Make key value storage abstractions more accurate (#1267)

* Layer do_atomically() abstractions properly

* Reduce allocs and DRY get_key_for_col()

* Parameterize HotColdDB with hot and cold item stores

* -impl Store for MemoryStore

* Replace Store uses with HotColdDB

* Ditch Store trait

* cargo fmt

* Style fix

* Readd missing dep that broke the build

Cargo.lock

@@ -4312,7 +4312,7 @@ checksum = "c111b5bd5695e56cffe5129854aa230b39c93a305372fdbb2668ca2394eea9f8"
 name = "slashing_protection"
 version = "0.1.0"
 dependencies = [
- "parking_lot 0.9.0",
+ "parking_lot 0.10.2",
  "r2d2",
  "r2d2_sqlite",
  "rayon",
@@ -4643,6 +4643,7 @@ dependencies = [
  "serde",
  "serde_derive",
  "slog",
+ "sloggers",
  "state_processing",
  "tempfile",
  "tree_hash",

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -40,7 +40,7 @@ use std::io::prelude::*;
 use std::sync::Arc;
 use std::time::{Duration, Instant};
 use store::iter::{BlockRootsIterator, ParentRootBlockIterator, StateRootsIterator};
-use store::{Error as DBError, Store};
+use store::{Error as DBError, HotColdDB};
 use types::*;
 
 // Text included in blocks.
@@ -148,10 +148,11 @@ pub struct HeadInfo {
 }
 
 pub trait BeaconChainTypes: Send + Sync + 'static {
-    type Store: store::Store<Self::EthSpec>;
+    type HotStore: store::ItemStore<Self::EthSpec>;
-    type StoreMigrator: Migrate<Self::EthSpec>;
+    type ColdStore: store::ItemStore<Self::EthSpec>;
+    type StoreMigrator: Migrate<Self::EthSpec, Self::HotStore, Self::ColdStore>;
     type SlotClock: slot_clock::SlotClock;
-    type Eth1Chain: Eth1ChainBackend<Self::EthSpec, Self::Store>;
+    type Eth1Chain: Eth1ChainBackend<Self::EthSpec>;
     type EthSpec: types::EthSpec;
     type EventHandler: EventHandler<Self::EthSpec>;
 }
@@ -161,7 +162,7 @@ pub trait BeaconChainTypes: Send + Sync + 'static {
 pub struct BeaconChain<T: BeaconChainTypes> {
     pub spec: ChainSpec,
     /// Persistent storage for blocks, states, etc. Typically an on-disk store, such as LevelDB.
-    pub store: Arc<T::Store>,
+    pub store: Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>,
     /// Database migrator for running background maintenance on the store.
     pub store_migrator: T::StoreMigrator,
     /// Reports the current slot, typically based upon the system clock.
@@ -185,7 +186,7 @@ pub struct BeaconChain<T: BeaconChainTypes> {
     /// Maintains a record of which validators have proposed blocks for each slot.
     pub observed_block_producers: ObservedBlockProducers<T::EthSpec>,
     /// Provides information from the Ethereum 1 (PoW) chain.
-    pub eth1_chain: Option<Eth1Chain<T::Eth1Chain, T::EthSpec, T::Store>>,
+    pub eth1_chain: Option<Eth1Chain<T::Eth1Chain, T::EthSpec>>,
     /// Stores a "snapshot" of the chain at the time the head-of-the-chain block was received.
     pub(crate) canonical_head: TimeoutRwLock<BeaconSnapshot<T::EthSpec>>,
     /// The root of the genesis block.
@@ -335,16 +336,18 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     pub fn forwards_iter_block_roots(
         &self,
         start_slot: Slot,
-    ) -> Result<<T::Store as Store<T::EthSpec>>::ForwardsBlockRootsIterator, Error> {
+    ) -> Result<impl Iterator<Item = Result<(Hash256, Slot), Error>>, Error> {
         let local_head = self.head()?;
 
-        Ok(T::Store::forwards_block_roots_iterator(
+        let iter = HotColdDB::forwards_block_roots_iterator(
             self.store.clone(),
             start_slot,
             local_head.beacon_state,
             local_head.beacon_block_root,
             &self.spec,
-        )?)
+        )?;
+
+        Ok(iter.map(|result| result.map_err(Into::into)))
     }
 
     /// Traverse backwards from `block_root` to find the block roots of its ancestors.

beacon_node/beacon_chain/src/builder.rs

@@ -24,7 +24,7 @@ use std::marker::PhantomData;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Duration;
-use store::Store;
+use store::{HotColdDB, ItemStore};
 use types::{
     BeaconBlock, BeaconState, ChainSpec, EthSpec, Hash256, Signature, SignedBeaconBlock, Slot,
 };
@@ -33,28 +33,48 @@ pub const PUBKEY_CACHE_FILENAME: &str = "pubkey_cache.ssz";
 
 /// An empty struct used to "witness" all the `BeaconChainTypes` traits. It has no user-facing
 /// functionality and only exists to satisfy the type system.
-pub struct Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>(
+pub struct Witness<
+    TStoreMigrator,
+    TSlotClock,
+    TEth1Backend,
+    TEthSpec,
+    TEventHandler,
+    THotStore,
+    TColdStore,
+>(
     PhantomData<(
-        TStore,
         TStoreMigrator,
         TSlotClock,
         TEth1Backend,
         TEthSpec,
         TEventHandler,
+        THotStore,
+        TColdStore,
     )>,
 );
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler> BeaconChainTypes
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
-    for Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
+    BeaconChainTypes
+    for Witness<
+        TStoreMigrator,
+        TSlotClock,
+        TEth1Backend,
+        TEthSpec,
+        TEventHandler,
+        THotStore,
+        TColdStore,
+    >
 where
-    TStore: Store<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore> + 'static,
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
 {
-    type Store = TStore;
+    type HotStore = THotStore;
+    type ColdStore = TColdStore;
     type StoreMigrator = TStoreMigrator;
     type SlotClock = TSlotClock;
     type Eth1Chain = TEth1Backend;
@@ -71,7 +91,7 @@ where
 ///
 /// See the tests for an example of a complete working example.
 pub struct BeaconChainBuilder<T: BeaconChainTypes> {
-    store: Option<Arc<T::Store>>,
+    store: Option<Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>>,
     store_migrator: Option<T::StoreMigrator>,
     canonical_head: Option<BeaconSnapshot<T::EthSpec>>,
     /// The finalized checkpoint to anchor the chain. May be genesis or a higher
@@ -80,7 +100,7 @@ pub struct BeaconChainBuilder<T: BeaconChainTypes> {
     genesis_block_root: Option<Hash256>,
     op_pool: Option<OperationPool<T::EthSpec>>,
     fork_choice: Option<ForkChoice<T>>,
-    eth1_chain: Option<Eth1Chain<T::Eth1Chain, T::EthSpec, T::Store>>,
+    eth1_chain: Option<Eth1Chain<T::Eth1Chain, T::EthSpec>>,
     event_handler: Option<T::EventHandler>,
     slot_clock: Option<T::SlotClock>,
     head_tracker: Option<HeadTracker>,
@@ -92,15 +112,24 @@ pub struct BeaconChainBuilder<T: BeaconChainTypes> {
     log: Option<Logger>,
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
     BeaconChainBuilder<
-        Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>,
+        Witness<
+            TStoreMigrator,
+            TSlotClock,
+            TEth1Backend,
+            TEthSpec,
+            TEventHandler,
+            THotStore,
+            TColdStore,
+        >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore> + 'static,
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
 {
@@ -142,7 +171,7 @@ where
     /// Sets the store (database).
     ///
     /// Should generally be called early in the build chain.
-    pub fn store(mut self, store: Arc<TStore>) -> Self {
+    pub fn store(mut self, store: Arc<HotColdDB<TEthSpec, THotStore, TColdStore>>) -> Self {
         self.store = Some(store);
         self
     }
@@ -379,7 +408,15 @@ where
         self,
     ) -> Result<
         BeaconChain<
-            Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>,
+            Witness<
+                TStoreMigrator,
+                TSlotClock,
+                TEth1Backend,
+                TEthSpec,
+                TEventHandler,
+                THotStore,
+                TColdStore,
+            >,
         >,
         String,
     > {
@@ -480,17 +517,26 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
     BeaconChainBuilder<
-        Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>,
+        Witness<
+            TStoreMigrator,
+            TSlotClock,
+            TEth1Backend,
+            TEthSpec,
+            TEventHandler,
+            THotStore,
+            TColdStore,
+        >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore> + 'static,
-    TStoreMigrator: Migrate<TEthSpec> + 'static,
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     /// Initializes a fork choice with the `ThreadSafeReducedTree` backend.
     ///
@@ -543,20 +589,22 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TSlotClock, TEthSpec, TEventHandler, THotStore, TColdStore>
     BeaconChainBuilder<
         Witness<
-            TStore,
             TStoreMigrator,
             TSlotClock,
-            CachingEth1Backend<TEthSpec, TStore>,
+            CachingEth1Backend<TEthSpec>,
             TEthSpec,
             TEventHandler,
+            THotStore,
+            TColdStore,
         >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore> + 'static,
     TSlotClock: SlotClock + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
@@ -572,12 +620,8 @@ where
             .log
             .as_ref()
             .ok_or_else(|| "dummy_eth1_backend requires a log".to_string())?;
-        let store = self
-            .store
-            .clone()
-            .ok_or_else(|| "dummy_eth1_backend requires a store.".to_string())?;
 
-        let backend = CachingEth1Backend::new(Eth1Config::default(), log.clone(), store);
+        let backend = CachingEth1Backend::new(Eth1Config::default(), log.clone());
 
         let mut eth1_chain = Eth1Chain::new(backend);
         eth1_chain.use_dummy_backend = true;
@@ -588,14 +632,23 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TEth1Backend, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
     BeaconChainBuilder<
-        Witness<TStore, TStoreMigrator, TestingSlotClock, TEth1Backend, TEthSpec, TEventHandler>,
+        Witness<
+            TStoreMigrator,
+            TestingSlotClock,
+            TEth1Backend,
+            TEthSpec,
+            TEventHandler,
+            THotStore,
+            TColdStore,
+        >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
 {
@@ -620,22 +673,24 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec>
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, THotStore, TColdStore>
     BeaconChainBuilder<
         Witness<
-            TStore,
             TStoreMigrator,
             TSlotClock,
             TEth1Backend,
             TEthSpec,
             NullEventHandler<TEthSpec>,
+            THotStore,
+            TColdStore,
         >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore> + 'static,
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
 {
     /// Sets the `BeaconChain` event handler to `NullEventHandler`.
@@ -665,12 +720,14 @@ fn genesis_block<T: EthSpec>(
 #[cfg(test)]
 mod test {
     use super::*;
-    use crate::migrate::{MemoryStore, NullMigrator};
+    use crate::migrate::NullMigrator;
     use eth2_hashing::hash;
     use genesis::{generate_deterministic_keypairs, interop_genesis_state};
     use sloggers::{null::NullLoggerBuilder, Build};
     use ssz::Encode;
     use std::time::Duration;
+    use store::config::StoreConfig;
+    use store::{HotColdDB, MemoryStore};
     use tempfile::tempdir;
     use types::{EthSpec, MinimalEthSpec, Slot};
 
@@ -687,7 +744,12 @@ mod test {
         let genesis_time = 13_371_337;
 
         let log = get_logger();
-        let store = Arc::new(MemoryStore::open());
+        let store: HotColdDB<
+            MinimalEthSpec,
+            MemoryStore<MinimalEthSpec>,
+            MemoryStore<MinimalEthSpec>,
+        > = HotColdDB::open_ephemeral(StoreConfig::default(), ChainSpec::minimal(), log.clone())
+            .unwrap();
         let spec = MinimalEthSpec::default_spec();
         let data_dir = tempdir().expect("should create temporary data_dir");
 
@@ -700,7 +762,7 @@ mod test {
 
         let chain = BeaconChainBuilder::new(MinimalEthSpec)
             .logger(log.clone())
-            .store(store)
+            .store(Arc::new(store))
             .store_migrator(NullMigrator)
             .data_dir(data_dir.path().to_path_buf())
             .genesis_state(genesis_state)

beacon_node/beacon_chain/src/eth1_chain.rs

@@ -10,8 +10,7 @@ use std::cmp::Ordering;
 use std::collections::HashMap;
 use std::iter::DoubleEndedIterator;
 use std::marker::PhantomData;
-use std::sync::Arc;
+use store::{DBColumn, Error as StoreError, StoreItem};
-use store::{DBColumn, Error as StoreError, Store, StoreItem};
 use types::{
     BeaconState, BeaconStateError, ChainSpec, Deposit, Eth1Data, EthSpec, Hash256, Slot, Unsigned,
     DEPOSIT_TREE_DEPTH,
@@ -75,24 +74,22 @@ impl StoreItem for SszEth1 {
 }
 
 /// Holds an `Eth1ChainBackend` and serves requests from the `BeaconChain`.
-pub struct Eth1Chain<T, E, S>
+pub struct Eth1Chain<T, E>
 where
-    T: Eth1ChainBackend<E, S>,
+    T: Eth1ChainBackend<E>,
     E: EthSpec,
-    S: Store<E>,
 {
     backend: T,
     /// When `true`, the backend will be ignored and dummy data from the 2019 Canada interop method
     /// will be used instead.
     pub use_dummy_backend: bool,
-    _phantom: PhantomData<(E, S)>,
+    _phantom: PhantomData<E>,
 }
 
-impl<T, E, S> Eth1Chain<T, E, S>
+impl<T, E> Eth1Chain<T, E>
 where
-    T: Eth1ChainBackend<E, S>,
+    T: Eth1ChainBackend<E>,
     E: EthSpec,
-    S: Store<E>,
 {
     pub fn new(backend: T) -> Self {
         Self {
@@ -110,7 +107,7 @@ where
         spec: &ChainSpec,
     ) -> Result<Eth1Data, Error> {
         if self.use_dummy_backend {
-            let dummy_backend: DummyEth1ChainBackend<E, S> = DummyEth1ChainBackend::default();
+            let dummy_backend: DummyEth1ChainBackend<E> = DummyEth1ChainBackend::default();
             dummy_backend.eth1_data(state, spec)
         } else {
             self.backend.eth1_data(state, spec)
@@ -132,7 +129,7 @@ where
         spec: &ChainSpec,
     ) -> Result<Vec<Deposit>, Error> {
         if self.use_dummy_backend {
-            let dummy_backend: DummyEth1ChainBackend<E, S> = DummyEth1ChainBackend::default();
+            let dummy_backend: DummyEth1ChainBackend<E> = DummyEth1ChainBackend::default();
             dummy_backend.queued_deposits(state, eth1_data_vote, spec)
         } else {
             self.backend.queued_deposits(state, eth1_data_vote, spec)
@@ -145,11 +142,10 @@ where
     pub fn from_ssz_container(
         ssz_container: &SszEth1,
         config: Eth1Config,
-        store: Arc<S>,
         log: &Logger,
     ) -> Result<Self, String> {
         let backend =
-            Eth1ChainBackend::from_bytes(&ssz_container.backend_bytes, config, store, log.clone())?;
+            Eth1ChainBackend::from_bytes(&ssz_container.backend_bytes, config, log.clone())?;
         Ok(Self {
             use_dummy_backend: ssz_container.use_dummy_backend,
             backend,
@@ -171,7 +167,7 @@ where
     }
 }
 
-pub trait Eth1ChainBackend<T: EthSpec, S: Store<T>>: Sized + Send + Sync {
+pub trait Eth1ChainBackend<T: EthSpec>: Sized + Send + Sync {
     /// Returns the `Eth1Data` that should be included in a block being produced for the given
     /// `state`.
     fn eth1_data(&self, beacon_state: &BeaconState<T>, spec: &ChainSpec)
@@ -195,12 +191,7 @@ pub trait Eth1ChainBackend<T: EthSpec, S: Store<T>>: Sized + Send + Sync {
     fn as_bytes(&self) -> Vec<u8>;
 
     /// Create a `Eth1ChainBackend` instance given encoded bytes.
-    fn from_bytes(
+    fn from_bytes(bytes: &[u8], config: Eth1Config, log: Logger) -> Result<Self, String>;
-        bytes: &[u8],
-        config: Eth1Config,
-        store: Arc<S>,
-        log: Logger,
-    ) -> Result<Self, String>;
 }
 
 /// Provides a simple, testing-only backend that generates deterministic, meaningless eth1 data.
@@ -208,9 +199,9 @@ pub trait Eth1ChainBackend<T: EthSpec, S: Store<T>>: Sized + Send + Sync {
 /// Never creates deposits, therefore the validator set is static.
 ///
 /// This was used in the 2019 Canada interop workshops.
-pub struct DummyEth1ChainBackend<T: EthSpec, S: Store<T>>(PhantomData<(T, S)>);
+pub struct DummyEth1ChainBackend<T: EthSpec>(PhantomData<T>);
 
-impl<T: EthSpec, S: Store<T>> Eth1ChainBackend<T, S> for DummyEth1ChainBackend<T, S> {
+impl<T: EthSpec> Eth1ChainBackend<T> for DummyEth1ChainBackend<T> {
     /// Produce some deterministic junk based upon the current epoch.
     fn eth1_data(&self, state: &BeaconState<T>, _spec: &ChainSpec) -> Result<Eth1Data, Error> {
         let current_epoch = state.current_epoch();
@@ -243,17 +234,12 @@ impl<T: EthSpec, S: Store<T>> Eth1ChainBackend<T, S> for DummyEth1ChainBackend<T
     }
 
     /// Create dummy eth1 backend.
-    fn from_bytes(
+    fn from_bytes(_bytes: &[u8], _config: Eth1Config, _log: Logger) -> Result<Self, String> {
-        _bytes: &[u8],
-        _config: Eth1Config,
-        _store: Arc<S>,
-        _log: Logger,
-    ) -> Result<Self, String> {
         Ok(Self(PhantomData))
     }
 }
 
-impl<T: EthSpec, S: Store<T>> Default for DummyEth1ChainBackend<T, S> {
+impl<T: EthSpec> Default for DummyEth1ChainBackend<T> {
     fn default() -> Self {
         Self(PhantomData)
     }
@@ -265,21 +251,19 @@ impl<T: EthSpec, S: Store<T>> Default for DummyEth1ChainBackend<T, S> {
 /// The `core` connects to some external eth1 client (e.g., Parity/Geth) and polls it for
 /// information.
 #[derive(Clone)]
-pub struct CachingEth1Backend<T: EthSpec, S> {
+pub struct CachingEth1Backend<T: EthSpec> {
     pub core: HttpService,
-    store: Arc<S>,
     log: Logger,
     _phantom: PhantomData<T>,
 }
 
-impl<T: EthSpec, S: Store<T>> CachingEth1Backend<T, S> {
+impl<T: EthSpec> CachingEth1Backend<T> {
     /// Instantiates `self` with empty caches.
     ///
     /// Does not connect to the eth1 node or start any tasks to keep the cache updated.
-    pub fn new(config: Eth1Config, log: Logger, store: Arc<S>) -> Self {
+    pub fn new(config: Eth1Config, log: Logger) -> Self {
         Self {
             core: HttpService::new(config, log.clone()),
-            store,
             log,
             _phantom: PhantomData,
         }
@@ -291,17 +275,16 @@ impl<T: EthSpec, S: Store<T>> CachingEth1Backend<T, S> {
     }
 
     /// Instantiates `self` from an existing service.
-    pub fn from_service(service: HttpService, store: Arc<S>) -> Self {
+    pub fn from_service(service: HttpService) -> Self {
         Self {
             log: service.log.clone(),
             core: service,
-            store,
             _phantom: PhantomData,
         }
     }
 }
 
-impl<T: EthSpec, S: Store<T>> Eth1ChainBackend<T, S> for CachingEth1Backend<T, S> {
+impl<T: EthSpec> Eth1ChainBackend<T> for CachingEth1Backend<T> {
     fn eth1_data(&self, state: &BeaconState<T>, spec: &ChainSpec) -> Result<Eth1Data, Error> {
         let period = T::SlotsPerEth1VotingPeriod::to_u64();
         let voting_period_start_slot = (state.slot / period) * period;
@@ -406,16 +389,10 @@ impl<T: EthSpec, S: Store<T>> Eth1ChainBackend<T, S> for CachingEth1Backend<T, S
     }
 
     /// Recover the cached backend from encoded bytes.
-    fn from_bytes(
+    fn from_bytes(bytes: &[u8], config: Eth1Config, log: Logger) -> Result<Self, String> {
-        bytes: &[u8],
-        config: Eth1Config,
-        store: Arc<S>,
-        log: Logger,
-    ) -> Result<Self, String> {
         let inner = HttpService::from_bytes(bytes, config, log.clone())?;
         Ok(Self {
             core: inner,
-            store,
             log,
             _phantom: PhantomData,
         })
@@ -572,17 +549,15 @@ mod test {
     mod eth1_chain_json_backend {
         use super::*;
         use eth1::DepositLog;
-        use store::MemoryStore;
         use types::test_utils::{generate_deterministic_keypair, TestingDepositBuilder};
 
-        fn get_eth1_chain() -> Eth1Chain<CachingEth1Backend<E, MemoryStore<E>>, E, MemoryStore<E>> {
+        fn get_eth1_chain() -> Eth1Chain<CachingEth1Backend<E>, E> {
             let eth1_config = Eth1Config {
                 ..Eth1Config::default()
             };
 
             let log = null_logger().unwrap();
-            let store = Arc::new(MemoryStore::open());
+            Eth1Chain::new(CachingEth1Backend::new(eth1_config, log))
-            Eth1Chain::new(CachingEth1Backend::new(eth1_config, log, store))
         }
 
         fn get_deposit_log(i: u64, spec: &ChainSpec) -> DepositLog {

beacon_node/beacon_chain/src/migrate.rs

@@ -9,14 +9,16 @@ use std::sync::Arc;
 use std::thread;
 use store::hot_cold_store::{process_finalization, HotColdDBError};
 use store::iter::{ParentRootBlockIterator, RootsIterator};
-use store::{Error, Store, StoreOp};
+use store::{Error, ItemStore, StoreOp};
 pub use store::{HotColdDB, MemoryStore};
 use types::*;
 use types::{BeaconState, EthSpec, Hash256, Slot};
 
 /// Trait for migration processes that update the database upon finalization.
-pub trait Migrate<E: EthSpec>: Send + Sync + 'static {
+pub trait Migrate<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>:
-    fn new(db: Arc<HotColdDB<E>>, log: Logger) -> Self;
+    Send + Sync + 'static
+{
+    fn new(db: Arc<HotColdDB<E, Hot, Cold>>, log: Logger) -> Self;
 
     fn process_finalization(
         &self,
@@ -30,13 +32,13 @@ pub trait Migrate<E: EthSpec>: Send + Sync + 'static {
     }
 
     /// Traverses live heads and prunes blocks and states of chains that we know can't be built
-    /// upon because finalization would prohibit it.  This is a optimisation intended to save disk
+    /// upon because finalization would prohibit it.  This is an optimisation intended to save disk
     /// space.
     ///
     /// Assumptions:
     ///  * It is called after every finalization.
     fn prune_abandoned_forks(
-        store: Arc<HotColdDB<E>>,
+        store: Arc<HotColdDB<E, Hot, Cold>>,
         head_tracker: Arc<HeadTracker>,
         old_finalized_block_hash: SignedBeaconBlockHash,
         new_finalized_block_hash: SignedBeaconBlockHash,
@@ -171,8 +173,8 @@ pub trait Migrate<E: EthSpec>: Send + Sync + 'static {
 /// Migrator that does nothing, for stores that don't need migration.
 pub struct NullMigrator;
 
-impl<E: EthSpec> Migrate<E> for NullMigrator {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> Migrate<E, Hot, Cold> for NullMigrator {
-    fn new(_: Arc<HotColdDB<E>>, _: Logger) -> Self {
+    fn new(_: Arc<HotColdDB<E, Hot, Cold>>, _: Logger) -> Self {
         NullMigrator
     }
 }
@@ -180,12 +182,14 @@ impl<E: EthSpec> Migrate<E> for NullMigrator {
 /// Migrator that immediately calls the store's migration function, blocking the current execution.
 ///
 /// Mostly useful for tests.
-pub struct BlockingMigrator<E: EthSpec> {
+pub struct BlockingMigrator<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
-    db: Arc<HotColdDB<E>>,
+    db: Arc<HotColdDB<E, Hot, Cold>>,
 }
 
-impl<E: EthSpec> Migrate<E> for BlockingMigrator<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> Migrate<E, Hot, Cold>
-    fn new(db: Arc<HotColdDB<E>>, _: Logger) -> Self {
+    for BlockingMigrator<E, Hot, Cold>
+{
+    fn new(db: Arc<HotColdDB<E, Hot, Cold>>, _: Logger) -> Self {
         BlockingMigrator { db }
     }
 
@@ -225,14 +229,16 @@ type MpscSender<E> = mpsc::Sender<(
 )>;
 
 /// Migrator that runs a background thread to migrate state from the hot to the cold database.
-pub struct BackgroundMigrator<E: EthSpec> {
+pub struct BackgroundMigrator<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
-    db: Arc<HotColdDB<E>>,
+    db: Arc<HotColdDB<E, Hot, Cold>>,
     tx_thread: Mutex<(MpscSender<E>, thread::JoinHandle<()>)>,
     log: Logger,
 }
 
-impl<E: EthSpec> Migrate<E> for BackgroundMigrator<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> Migrate<E, Hot, Cold>
-    fn new(db: Arc<HotColdDB<E>>, log: Logger) -> Self {
+    for BackgroundMigrator<E, Hot, Cold>
+{
+    fn new(db: Arc<HotColdDB<E, Hot, Cold>>, log: Logger) -> Self {
         let tx_thread = Mutex::new(Self::spawn_thread(db.clone(), log.clone()));
         Self { db, tx_thread, log }
     }
@@ -283,7 +289,7 @@ impl<E: EthSpec> Migrate<E> for BackgroundMigrator<E> {
     }
 }
 
-impl<E: EthSpec> BackgroundMigrator<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> BackgroundMigrator<E, Hot, Cold> {
     /// Return true if a migration needs to be performed, given a new `finalized_slot`.
     fn needs_migration(&self, finalized_slot: Slot, max_finality_distance: u64) -> bool {
         let finality_distance = finalized_slot - self.db.get_split_slot();
@@ -294,7 +300,7 @@ impl<E: EthSpec> BackgroundMigrator<E> {
     ///
     /// Return a channel handle for sending new finalized states to the thread.
     fn spawn_thread(
-        db: Arc<HotColdDB<E>>,
+        db: Arc<HotColdDB<E, Hot, Cold>>,
         log: Logger,
     ) -> (
         mpsc::Sender<(

beacon_node/beacon_chain/src/test_utils.rs

@@ -18,7 +18,7 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 use std::sync::Arc;
 use std::time::Duration;
-use store::{HotColdDB, MemoryStore, Store};
+use store::{config::StoreConfig, HotColdDB, ItemStore, LevelDB, MemoryStore};
 use tempfile::{tempdir, TempDir};
 use tree_hash::TreeHash;
 use types::{
@@ -34,17 +34,19 @@ pub const HARNESS_GENESIS_TIME: u64 = 1_567_552_690;
 // This parameter is required by a builder but not used because we use the `TestingSlotClock`.
 pub const HARNESS_SLOT_TIME: Duration = Duration::from_secs(1);
 
-pub type BaseHarnessType<TStore, TStoreMigrator, TEthSpec> = Witness<
+pub type BaseHarnessType<TStoreMigrator, TEthSpec, THotStore, TColdStore> = Witness<
-    TStore,
     TStoreMigrator,
     TestingSlotClock,
-    CachingEth1Backend<TEthSpec, TStore>,
+    CachingEth1Backend<TEthSpec>,
     TEthSpec,
     NullEventHandler<TEthSpec>,
+    THotStore,
+    TColdStore,
 >;
 
-pub type HarnessType<E> = BaseHarnessType<MemoryStore<E>, NullMigrator, E>;
+pub type HarnessType<E> = BaseHarnessType<NullMigrator, E, MemoryStore<E>, MemoryStore<E>>;
-pub type DiskHarnessType<E> = BaseHarnessType<HotColdDB<E>, BlockingMigrator<E>, E>;
+pub type DiskHarnessType<E> =
+    BaseHarnessType<BlockingMigrator<E, LevelDB<E>, LevelDB<E>>, E, LevelDB<E>, LevelDB<E>>;
 
 /// Indicates how the `BeaconChainHarness` should produce blocks.
 #[derive(Clone, Copy, Debug)]
@@ -84,12 +86,12 @@ pub struct BeaconChainHarness<T: BeaconChainTypes> {
 
 impl<E: EthSpec> BeaconChainHarness<HarnessType<E>> {
     /// Instantiate a new harness with `validator_count` initial validators.
-    pub fn new(eth_spec_instance: E, keypairs: Vec<Keypair>) -> Self {
+    pub fn new(eth_spec_instance: E, keypairs: Vec<Keypair>, config: StoreConfig) -> Self {
         // Setting the target aggregators to really high means that _all_ validators in the
         // committee are required to produce an aggregate. This is overkill, however with small
         // validator counts it's the only way to be certain there is _at least one_ aggregator per
         // committee.
-        Self::new_with_target_aggregators(eth_spec_instance, keypairs, 1 << 32)
+        Self::new_with_target_aggregators(eth_spec_instance, keypairs, 1 << 32, config)
     }
 
     /// Instantiate a new harness with `validator_count` initial validators and a custom
@@ -98,6 +100,7 @@ impl<E: EthSpec> BeaconChainHarness<HarnessType<E>> {
         eth_spec_instance: E,
         keypairs: Vec<Keypair>,
         target_aggregators_per_committee: u64,
+        config: StoreConfig,
     ) -> Self {
         let data_dir = tempdir().expect("should create temporary data_dir");
         let mut spec = E::default_spec();
@@ -105,11 +108,11 @@ impl<E: EthSpec> BeaconChainHarness<HarnessType<E>> {
         spec.target_aggregators_per_committee = target_aggregators_per_committee;
 
         let log = NullLoggerBuilder.build().expect("logger should build");
-
+        let store = HotColdDB::open_ephemeral(config, spec.clone(), log.clone()).unwrap();
         let chain = BeaconChainBuilder::new(eth_spec_instance)
-            .logger(log.clone())
+            .logger(log)
             .custom_spec(spec.clone())
-            .store(Arc::new(MemoryStore::open()))
+            .store(Arc::new(store))
             .store_migrator(NullMigrator)
             .data_dir(data_dir.path().to_path_buf())
             .genesis_state(
@@ -140,7 +143,7 @@ impl<E: EthSpec> BeaconChainHarness<DiskHarnessType<E>> {
     /// Instantiate a new harness with `validator_count` initial validators.
     pub fn new_with_disk_store(
         eth_spec_instance: E,
-        store: Arc<HotColdDB<E>>,
+        store: Arc<HotColdDB<E, LevelDB<E>, LevelDB<E>>>,
         keypairs: Vec<Keypair>,
     ) -> Self {
         let data_dir = tempdir().expect("should create temporary data_dir");
@@ -180,7 +183,7 @@ impl<E: EthSpec> BeaconChainHarness<DiskHarnessType<E>> {
     /// Instantiate a new harness with `validator_count` initial validators.
     pub fn resume_from_disk_store(
         eth_spec_instance: E,
-        store: Arc<HotColdDB<E>>,
+        store: Arc<HotColdDB<E, LevelDB<E>, LevelDB<E>>>,
         keypairs: Vec<Keypair>,
         data_dir: TempDir,
     ) -> Self {
@@ -192,7 +195,10 @@ impl<E: EthSpec> BeaconChainHarness<DiskHarnessType<E>> {
             .logger(log.clone())
             .custom_spec(spec)
             .store(store.clone())
-            .store_migrator(<BlockingMigrator<_> as Migrate<E>>::new(store, log.clone()))
+            .store_migrator(<BlockingMigrator<_, _, _> as Migrate<E, _, _>>::new(
+                store,
+                log.clone(),
+            ))
             .data_dir(data_dir.path().to_path_buf())
             .resume_from_db()
             .expect("should resume beacon chain from db")
@@ -215,11 +221,12 @@ impl<E: EthSpec> BeaconChainHarness<DiskHarnessType<E>> {
     }
 }
 
-impl<S, M, E> BeaconChainHarness<BaseHarnessType<S, M, E>>
+impl<M, E, Hot, Cold> BeaconChainHarness<BaseHarnessType<M, E, Hot, Cold>>
 where
-    S: Store<E>,
+    M: Migrate<E, Hot, Cold>,
-    M: Migrate<E>,
     E: EthSpec,
+    Hot: ItemStore<E>,
+    Cold: ItemStore<E>,
 {
     /// Advance the slot of the `BeaconChain`.
     ///

beacon_node/beacon_chain/tests/attestation_production.rs

@@ -7,6 +7,7 @@ use beacon_chain::{
     test_utils::{AttestationStrategy, BeaconChainHarness, BlockStrategy},
     StateSkipConfig,
 };
+use store::config::StoreConfig;
 use tree_hash::TreeHash;
 use types::{AggregateSignature, EthSpec, Keypair, MainnetEthSpec, RelativeEpoch, Slot};
 
@@ -25,7 +26,11 @@ lazy_static! {
 fn produces_attestations() {
     let num_blocks_produced = MainnetEthSpec::slots_per_epoch() * 4;
 
-    let harness = BeaconChainHarness::new(MainnetEthSpec, KEYPAIRS[..].to_vec());
+    let harness = BeaconChainHarness::new(
+        MainnetEthSpec,
+        KEYPAIRS[..].to_vec(),
+        StoreConfig::default(),
+    );
 
     // Skip past the genesis slot.
     harness.advance_slot();

beacon_node/beacon_chain/tests/attestation_verification.rs

@@ -9,7 +9,7 @@ use beacon_chain::{
     BeaconChain, BeaconChainTypes,
 };
 use state_processing::per_slot_processing;
-use store::Store;
+use store::config::StoreConfig;
 use tree_hash::TreeHash;
 use types::{
     test_utils::generate_deterministic_keypair, AggregateSignature, Attestation, EthSpec, Hash256,
@@ -36,6 +36,7 @@ fn get_harness(validator_count: usize) -> BeaconChainHarness<HarnessType<E>> {
         // A kind-of arbitrary number that ensures that _some_ validators are aggregators, but
         // not all.
         4,
+        StoreConfig::default(),
     );
 
     harness.advance_slot();

beacon_node/beacon_chain/tests/block_verification.rs

@@ -7,6 +7,7 @@ use beacon_chain::{
     test_utils::{AttestationStrategy, BeaconChainHarness, BlockStrategy, HarnessType},
     BeaconSnapshot, BlockError,
 };
+use store::config::StoreConfig;
 use types::{
     test_utils::generate_deterministic_keypair, AggregateSignature, AttestationData,
     AttesterSlashing, Checkpoint, Deposit, DepositData, Epoch, EthSpec, Hash256,
@@ -47,7 +48,11 @@ fn get_chain_segment() -> Vec<BeaconSnapshot<E>> {
 }
 
 fn get_harness(validator_count: usize) -> BeaconChainHarness<HarnessType<E>> {
-    let harness = BeaconChainHarness::new(MainnetEthSpec, KEYPAIRS[0..validator_count].to_vec());
+    let harness = BeaconChainHarness::new(
+        MainnetEthSpec,
+        KEYPAIRS[0..validator_count].to_vec(),
+        StoreConfig::default(),
+    );
 
     harness.advance_slot();
 

beacon_node/beacon_chain/tests/persistence_tests.rs

@@ -9,7 +9,7 @@ use beacon_chain::{
 };
 use sloggers::{null::NullLoggerBuilder, Build};
 use std::sync::Arc;
-use store::{HotColdDB, StoreConfig};
+use store::{HotColdDB, LevelDB, StoreConfig};
 use tempfile::{tempdir, TempDir};
 use types::{EthSpec, Keypair, MinimalEthSpec};
 
@@ -23,7 +23,7 @@ lazy_static! {
     static ref KEYPAIRS: Vec<Keypair> = types::test_utils::generate_deterministic_keypairs(VALIDATOR_COUNT);
 }
 
-fn get_store(db_path: &TempDir) -> Arc<HotColdDB<E>> {
+fn get_store(db_path: &TempDir) -> Arc<HotColdDB<E, LevelDB<E>, LevelDB<E>>> {
     let spec = E::default_spec();
     let hot_path = db_path.path().join("hot_db");
     let cold_path = db_path.path().join("cold_db");

beacon_node/beacon_chain/tests/store_tests.rs

@@ -16,7 +16,7 @@ use std::collections::HashSet;
 use std::sync::Arc;
 use store::{
     iter::{BlockRootsIterator, StateRootsIterator},
-    HotColdDB, Store, StoreConfig,
+    HotColdDB, LevelDB, StoreConfig,
 };
 use tempfile::{tempdir, TempDir};
 use tree_hash::TreeHash;
@@ -35,7 +35,7 @@ lazy_static! {
 type E = MinimalEthSpec;
 type TestHarness = BeaconChainHarness<DiskHarnessType<E>>;
 
-fn get_store(db_path: &TempDir) -> Arc<HotColdDB<E>> {
+fn get_store(db_path: &TempDir) -> Arc<HotColdDB<E, LevelDB<E>, LevelDB<E>>> {
     let spec = MinimalEthSpec::default_spec();
     let hot_path = db_path.path().join("hot_db");
     let cold_path = db_path.path().join("cold_db");
@@ -47,7 +47,10 @@ fn get_store(db_path: &TempDir) -> Arc<HotColdDB<E>> {
     )
 }
 
-fn get_harness(store: Arc<HotColdDB<E>>, validator_count: usize) -> TestHarness {
+fn get_harness(
+    store: Arc<HotColdDB<E, LevelDB<E>, LevelDB<E>>>,
+    validator_count: usize,
+) -> TestHarness {
     let harness = BeaconChainHarness::new_with_disk_store(
         MinimalEthSpec,
         store,
@@ -1310,7 +1313,7 @@ fn check_finalization(harness: &TestHarness, expected_slot: u64) {
 }
 
 /// Check that the HotColdDB's split_slot is equal to the start slot of the last finalized epoch.
-fn check_split_slot(harness: &TestHarness, store: Arc<HotColdDB<E>>) {
+fn check_split_slot(harness: &TestHarness, store: Arc<HotColdDB<E, LevelDB<E>, LevelDB<E>>>) {
     let split_slot = store.get_split_slot();
     assert_eq!(
         harness
@@ -1361,7 +1364,7 @@ fn check_chain_dump(harness: &TestHarness, expected_len: u64) {
         .collect::<Vec<_>>();
 
     let head = harness.chain.head().expect("should get head");
-    let mut forward_block_roots = Store::forwards_block_roots_iterator(
+    let mut forward_block_roots = HotColdDB::forwards_block_roots_iterator(
         harness.chain.store.clone(),
         Slot::new(0),
         head.beacon_state,

beacon_node/beacon_chain/tests/tests.rs

@@ -13,7 +13,7 @@ use operation_pool::PersistedOperationPool;
 use state_processing::{
     per_slot_processing, per_slot_processing::Error as SlotProcessingError, EpochProcessingError,
 };
-use store::Store;
+use store::config::StoreConfig;
 use types::{BeaconStateError, EthSpec, Hash256, Keypair, MinimalEthSpec, RelativeEpoch, Slot};
 
 // Should ideally be divisible by 3.
@@ -25,7 +25,11 @@ lazy_static! {
 }
 
 fn get_harness(validator_count: usize) -> BeaconChainHarness<HarnessType<MinimalEthSpec>> {
-    let harness = BeaconChainHarness::new(MinimalEthSpec, KEYPAIRS[0..validator_count].to_vec());
+    let harness = BeaconChainHarness::new(
+        MinimalEthSpec,
+        KEYPAIRS[0..validator_count].to_vec(),
+        StoreConfig::default(),
+    );
 
     harness.advance_slot();
 

beacon_node/client/src/builder.rs

@@ -5,9 +5,9 @@ use beacon_chain::events::TeeEventHandler;
 use beacon_chain::{
     builder::{BeaconChainBuilder, Witness},
     eth1_chain::{CachingEth1Backend, Eth1Chain},
-    migrate::{BackgroundMigrator, Migrate, NullMigrator},
+    migrate::{BackgroundMigrator, Migrate},
     slot_clock::{SlotClock, SystemTimeSlotClock},
-    store::{HotColdDB, MemoryStore, Store, StoreConfig},
+    store::{HotColdDB, ItemStore, LevelDB, StoreConfig},
     BeaconChain, BeaconChainTypes, Eth1ChainBackend, EventHandler,
 };
 use bus::Bus;
@@ -50,7 +50,7 @@ pub const ETH1_GENESIS_UPDATE_INTERVAL_MILLIS: u64 = 7_000;
 /// `self.memory_store(..)` has been called.
 pub struct ClientBuilder<T: BeaconChainTypes> {
     slot_clock: Option<T::SlotClock>,
-    store: Option<Arc<T::Store>>,
+    store: Option<Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>>,
     store_migrator: Option<T::StoreMigrator>,
     runtime_context: Option<RuntimeContext<T::EthSpec>>,
     chain_spec: Option<ChainSpec>,
@@ -65,17 +65,26 @@ pub struct ClientBuilder<T: BeaconChainTypes> {
     eth_spec_instance: T::EthSpec,
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
     ClientBuilder<
-        Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>,
+        Witness<
+            TStoreMigrator,
+            TSlotClock,
+            TEth1Backend,
+            TEthSpec,
+            TEventHandler,
+            THotStore,
+            TColdStore,
+        >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore>,
-    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + Clone + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     /// Instantiates a new, empty builder.
     ///
@@ -350,8 +359,17 @@ where
     /// If type inference errors are being raised, see the comment on the definition of `Self`.
     pub fn build(
         self,
-    ) -> Client<Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>>
+    ) -> Client<
-    {
+        Witness<
+            TStoreMigrator,
+            TSlotClock,
+            TEth1Backend,
+            TEthSpec,
+            TEventHandler,
+            THotStore,
+            TColdStore,
+        >,
+    > {
         Client {
             beacon_chain: self.beacon_chain,
             network_globals: self.network_globals,
@@ -361,17 +379,26 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
     ClientBuilder<
-        Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>,
+        Witness<
+            TStoreMigrator,
+            TSlotClock,
+            TEth1Backend,
+            TEthSpec,
+            TEventHandler,
+            THotStore,
+            TColdStore,
+        >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore>,
-    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + Clone + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     /// Consumes the internal `BeaconChainBuilder`, attaching the resulting `BeaconChain` to self.
     pub fn build_beacon_chain(mut self) -> Result<Self, String> {
@@ -401,23 +428,25 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec>
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, THotStore, TColdStore>
     ClientBuilder<
         Witness<
-            TStore,
             TStoreMigrator,
             TSlotClock,
             TEth1Backend,
             TEthSpec,
             WebSocketSender<TEthSpec>,
+            THotStore,
+            TColdStore,
         >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore>,
-    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     /// Specifies that the `BeaconChain` should publish events using the WebSocket server.
     pub fn websocket_event_handler(mut self, config: WebSocketConfig) -> Result<Self, String> {
@@ -442,23 +471,25 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec>
+impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, THotStore, TColdStore>
     ClientBuilder<
         Witness<
-            TStore,
             TStoreMigrator,
             TSlotClock,
             TEth1Backend,
             TEthSpec,
             TeeEventHandler<TEthSpec>,
+            THotStore,
+            TColdStore,
         >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore>,
-    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     /// Specifies that the `BeaconChain` should publish events using the WebSocket server.
     pub fn tee_event_handler(
@@ -490,18 +521,19 @@ where
 impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     ClientBuilder<
         Witness<
-            HotColdDB<TEthSpec>,
             TStoreMigrator,
             TSlotClock,
             TEth1Backend,
             TEthSpec,
             TEventHandler,
+            LevelDB<TEthSpec>,
+            LevelDB<TEthSpec>,
         >,
     >
 where
     TSlotClock: SlotClock + 'static,
-    TStoreMigrator: Migrate<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, LevelDB<TEthSpec>, LevelDB<TEthSpec>> + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, HotColdDB<TEthSpec>> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
 {
@@ -529,50 +561,25 @@ where
     }
 }
 
-impl<TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
+impl<TSlotClock, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
     ClientBuilder<
         Witness<
-            MemoryStore<TEthSpec>,
+            BackgroundMigrator<TEthSpec, THotStore, TColdStore>,
-            NullMigrator,
             TSlotClock,
             TEth1Backend,
             TEthSpec,
             TEventHandler,
+            THotStore,
+            TColdStore,
         >,
     >
 where
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, MemoryStore<TEthSpec>> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
-    TEthSpec: EthSpec + 'static,
-    TEventHandler: EventHandler<TEthSpec> + 'static,
-{
-    /// Specifies that the `Client` should use a `MemoryStore` database.
-    ///
-    /// Also sets the `store_migrator` to the `NullMigrator`, as that's the only viable choice.
-    pub fn memory_store(mut self) -> Self {
-        let store = MemoryStore::open();
-        self.store = Some(Arc::new(store));
-        self.store_migrator = Some(NullMigrator);
-        self
-    }
-}
-
-impl<TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
-    ClientBuilder<
-        Witness<
-            HotColdDB<TEthSpec>,
-            BackgroundMigrator<TEthSpec>,
-            TSlotClock,
-            TEth1Backend,
-            TEthSpec,
-            TEventHandler,
-        >,
-    >
-where
-    TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, HotColdDB<TEthSpec>> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     pub fn background_migrator(mut self) -> Result<Self, String> {
         let context = self
@@ -588,23 +595,25 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TSlotClock, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TSlotClock, TEthSpec, TEventHandler, THotStore, TColdStore>
     ClientBuilder<
         Witness<
-            TStore,
             TStoreMigrator,
             TSlotClock,
-            CachingEth1Backend<TEthSpec, TStore>,
+            CachingEth1Backend<TEthSpec>,
             TEthSpec,
             TEventHandler,
+            THotStore,
+            TColdStore,
         >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore>,
-    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     /// Specifies that the `BeaconChain` should cache eth1 blocks/logs from a remote eth1 node
     /// (e.g., Parity/Geth) and refer to that cache when collecting deposits or eth1 votes during
@@ -618,10 +627,6 @@ where
         let beacon_chain_builder = self
             .beacon_chain_builder
             .ok_or_else(|| "caching_eth1_backend requires a beacon_chain_builder")?;
-        let store = self
-            .store
-            .clone()
-            .ok_or_else(|| "caching_eth1_backend requires a store".to_string())?;
 
         let backend = if let Some(eth1_service_from_genesis) = self.eth1_service {
             eth1_service_from_genesis.update_config(config)?;
@@ -636,7 +641,7 @@ where
             // adding earlier blocks too.
             eth1_service_from_genesis.drop_block_cache();
 
-            CachingEth1Backend::from_service(eth1_service_from_genesis, store)
+            CachingEth1Backend::from_service(eth1_service_from_genesis)
         } else {
             beacon_chain_builder
                 .get_persisted_eth1_backend()?
@@ -644,18 +649,11 @@ where
                     Eth1Chain::from_ssz_container(
                         &persisted,
                         config.clone(),
-                        store.clone(),
                         &context.log().clone(),
                     )
                     .map(|chain| chain.into_backend())
                 })
-                .unwrap_or_else(|| {
+                .unwrap_or_else(|| Ok(CachingEth1Backend::new(config, context.log().clone())))?
-                    Ok(CachingEth1Backend::new(
-                        config,
-                        context.log().clone(),
-                        store,
-                    ))
-                })?
         };
 
         self.eth1_service = None;
@@ -699,16 +697,25 @@ where
     }
 }
 
-impl<TStore, TStoreMigrator, TEth1Backend, TEthSpec, TEventHandler>
+impl<TStoreMigrator, TEth1Backend, TEthSpec, TEventHandler, THotStore, TColdStore>
     ClientBuilder<
-        Witness<TStore, TStoreMigrator, SystemTimeSlotClock, TEth1Backend, TEthSpec, TEventHandler>,
+        Witness<
+            TStoreMigrator,
+            SystemTimeSlotClock,
+            TEth1Backend,
+            TEthSpec,
+            TEventHandler,
+            THotStore,
+            TColdStore,
+        >,
     >
 where
-    TStore: Store<TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec, THotStore, TColdStore>,
-    TStoreMigrator: Migrate<TEthSpec>,
+    TEth1Backend: Eth1ChainBackend<TEthSpec> + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
+    THotStore: ItemStore<TEthSpec> + 'static,
+    TColdStore: ItemStore<TEthSpec> + 'static,
 {
     /// Specifies that the slot clock should read the time from the computers system clock.
     pub fn system_time_slot_clock(mut self) -> Result<Self, String> {

beacon_node/network/src/attestation_service/tests/mod.rs

@@ -17,19 +17,21 @@ mod tests {
     use sloggers::{null::NullLoggerBuilder, Build};
     use slot_clock::{SlotClock, SystemTimeSlotClock};
     use std::time::{Duration, SystemTime};
-    use store::MemoryStore;
+    use store::config::StoreConfig;
+    use store::{HotColdDB, MemoryStore};
     use tempfile::tempdir;
     use types::{CommitteeIndex, EnrForkId, EthSpec, MinimalEthSpec};
 
     const SLOT_DURATION_MILLIS: u64 = 200;
 
     type TestBeaconChainType = Witness<
-        MemoryStore<MinimalEthSpec>,
         NullMigrator,
         SystemTimeSlotClock,
-        CachingEth1Backend<MinimalEthSpec, MemoryStore<MinimalEthSpec>>,
+        CachingEth1Backend<MinimalEthSpec>,
         MinimalEthSpec,
         NullEventHandler<MinimalEthSpec>,
+        MemoryStore<MinimalEthSpec>,
+        MemoryStore<MinimalEthSpec>,
     >;
 
     pub struct TestBeaconChain {
@@ -44,11 +46,14 @@ mod tests {
             let keypairs = generate_deterministic_keypairs(1);
 
             let log = get_logger();
+            let store =
+                HotColdDB::open_ephemeral(StoreConfig::default(), spec.clone(), log.clone())
+                    .unwrap();
             let chain = Arc::new(
                 BeaconChainBuilder::new(MinimalEthSpec)
                     .logger(log.clone())
                     .custom_spec(spec.clone())
-                    .store(Arc::new(MemoryStore::open()))
+                    .store(Arc::new(store))
                     .store_migrator(NullMigrator)
                     .data_dir(data_dir.path().to_path_buf())
                     .genesis_state(
@@ -85,7 +90,7 @@ mod tests {
     }
 
     lazy_static! {
-        static ref CHAIN: TestBeaconChain = { TestBeaconChain::new_with_system_clock() };
+        static ref CHAIN: TestBeaconChain = TestBeaconChain::new_with_system_clock();
     }
 
     fn get_attestation_service() -> AttestationService<TestBeaconChainType> {

beacon_node/network/src/persisted_dht.rs

@@ -1,13 +1,15 @@
 use eth2_libp2p::Enr;
 use rlp;
 use std::sync::Arc;
-use store::{DBColumn, Error as StoreError, Store, StoreItem};
+use store::{DBColumn, Error as StoreError, HotColdDB, ItemStore, StoreItem};
 use types::{EthSpec, Hash256};
 
 /// 32-byte key for accessing the `DhtEnrs`.
 pub const DHT_DB_KEY: &str = "PERSISTEDDHTPERSISTEDDHTPERSISTE";
 
-pub fn load_dht<T: Store<E>, E: EthSpec>(store: Arc<T>) -> Vec<Enr> {
+pub fn load_dht<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>(
+    store: Arc<HotColdDB<E, Hot, Cold>>,
+) -> Vec<Enr> {
     // Load DHT from store
     let key = Hash256::from_slice(&DHT_DB_KEY.as_bytes());
     match store.get_item(&key) {
@@ -20,8 +22,8 @@ pub fn load_dht<T: Store<E>, E: EthSpec>(store: Arc<T>) -> Vec<Enr> {
 }
 
 /// Attempt to persist the ENR's in the DHT to `self.store`.
-pub fn persist_dht<T: Store<E>, E: EthSpec>(
+pub fn persist_dht<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>(
-    store: Arc<T>,
+    store: Arc<HotColdDB<E, Hot, Cold>>,
     enrs: Vec<Enr>,
 ) -> Result<(), store::Error> {
     let key = Hash256::from_slice(&DHT_DB_KEY.as_bytes());
@@ -56,14 +58,19 @@ impl StoreItem for PersistedDht {
 mod tests {
     use super::*;
     use eth2_libp2p::Enr;
+    use sloggers::{null::NullLoggerBuilder, Build};
     use std::str::FromStr;
-    use std::sync::Arc;
+    use store::config::StoreConfig;
-    use store::{MemoryStore, Store};
+    use store::{HotColdDB, MemoryStore};
-    use types::Hash256;
+    use types::{ChainSpec, Hash256, MinimalEthSpec};
-    use types::MinimalEthSpec;
     #[test]
     fn test_persisted_dht() {
-        let store = Arc::new(MemoryStore::<MinimalEthSpec>::open());
+        let log = NullLoggerBuilder.build().unwrap();
+        let store: HotColdDB<
+            MinimalEthSpec,
+            MemoryStore<MinimalEthSpec>,
+            MemoryStore<MinimalEthSpec>,
+        > = HotColdDB::open_ephemeral(StoreConfig::default(), ChainSpec::minimal(), log).unwrap();
         let enrs = vec![Enr::from_str("enr:-IS4QHCYrYZbAKWCBRlAy5zzaDZXJBGkcnh4MHcBFZntXNFrdvJjX04jRzjzCBOonrkTfj499SZuOh8R33Ls8RRcy5wBgmlkgnY0gmlwhH8AAAGJc2VjcDI1NmsxoQPKY0yuDUmstAHYpMa2_oxVtw0RW_QAdpzBQA8yWM0xOIN1ZHCCdl8").unwrap()];
         let key = Hash256::from_slice(&DHT_DB_KEY.as_bytes());
         store

beacon_node/network/src/router/processor.rs

@@ -13,7 +13,6 @@ use itertools::process_results;
 use slog::{debug, error, o, trace, warn};
 use ssz::Encode;
 use std::sync::Arc;
-use store::Store;
 use tokio::sync::mpsc;
 use types::{
     Attestation, ChainSpec, Epoch, EthSpec, Hash256, SignedAggregateAndProof, SignedBeaconBlock,

beacon_node/network/src/service.rs

@@ -17,6 +17,7 @@ use rest_types::ValidatorSubscription;
 use slog::{debug, error, info, o, trace};
 use std::sync::Arc;
 use std::time::Duration;
+use store::HotColdDB;
 use tokio::sync::mpsc;
 use tokio::time::Delay;
 use types::EthSpec;
@@ -40,7 +41,7 @@ pub struct NetworkService<T: BeaconChainTypes> {
     /// lighthouse.
     router_send: mpsc::UnboundedSender<RouterMessage<T::EthSpec>>,
     /// A reference to lighthouse's database to persist the DHT.
-    store: Arc<T::Store>,
+    store: Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>,
     /// A collection of global variables, accessible outside of the network service.
     network_globals: Arc<NetworkGlobals<T::EthSpec>>,
     /// A delay that expires when a new fork takes place.
@@ -78,7 +79,7 @@ impl<T: BeaconChainTypes> NetworkService<T> {
         let (network_globals, mut libp2p) =
             LibP2PService::new(executor.clone(), config, enr_fork_id, &network_log)?;
 
-        for enr in load_dht::<T::Store, T::EthSpec>(store.clone()) {
+        for enr in load_dht::<T::EthSpec, T::HotStore, T::ColdStore>(store.clone()) {
             libp2p.swarm.add_enr(enr);
         }
 
@@ -142,7 +143,7 @@ fn spawn_service<T: BeaconChainTypes>(
                         "Number of peers" => format!("{}", enrs.len()),
                     );
 
-                    match persist_dht::<T::Store, T::EthSpec>(service.store.clone(), enrs) {
+                    match persist_dht::<T::EthSpec, T::HotStore, T::ColdStore>(service.store.clone(), enrs) {
                         Err(e) => error!(
                             service.log,
                             "Failed to persist DHT on drop";

beacon_node/network/src/service/tests.rs

@@ -9,6 +9,7 @@ mod tests {
     use sloggers::{null::NullLoggerBuilder, Build};
     use std::str::FromStr;
     use std::sync::Arc;
+    use store::config::StoreConfig;
     use tokio::runtime::Runtime;
     use types::{test_utils::generate_deterministic_keypairs, MinimalEthSpec};
 
@@ -22,7 +23,12 @@ mod tests {
         let log = get_logger();
 
         let beacon_chain = Arc::new(
-            BeaconChainHarness::new(MinimalEthSpec, generate_deterministic_keypairs(8)).chain,
+            BeaconChainHarness::new(
+                MinimalEthSpec,
+                generate_deterministic_keypairs(8),
+                StoreConfig::default(),
+            )
+            .chain,
         );
 
         let store = beacon_chain.store.clone();

beacon_node/rest_api/src/beacon.rs

@@ -13,7 +13,6 @@ use rest_types::{
 };
 use std::io::Write;
 use std::sync::Arc;
-use store::Store;
 
 use slog::{error, Logger};
 use types::{

beacon_node/rest_api/src/helpers.rs

@@ -8,7 +8,7 @@ use hyper::{Body, Request};
 use itertools::process_results;
 use network::NetworkMessage;
 use ssz::Decode;
-use store::{iter::AncestorIter, Store};
+use store::iter::AncestorIter;
 use types::{
     BeaconState, CommitteeIndex, Epoch, EthSpec, Hash256, RelativeEpoch, SignedBeaconBlock, Slot,
 };

beacon_node/src/lib.rs

@@ -11,7 +11,8 @@ pub use config::{get_data_dir, get_eth2_testnet_config, get_testnet_dir};
 pub use eth2_config::Eth2Config;
 
 use beacon_chain::events::TeeEventHandler;
-use beacon_chain::migrate::{BackgroundMigrator, HotColdDB};
+use beacon_chain::migrate::BackgroundMigrator;
+use beacon_chain::store::LevelDB;
 use beacon_chain::{
     builder::Witness, eth1_chain::CachingEth1Backend, slot_clock::SystemTimeSlotClock,
 };
@@ -25,12 +26,13 @@ use types::EthSpec;
 /// A type-alias to the tighten the definition of a production-intended `Client`.
 pub type ProductionClient<E> = Client<
     Witness<
-        HotColdDB<E>,
+        BackgroundMigrator<E, LevelDB<E>, LevelDB<E>>,
-        BackgroundMigrator<E>,
         SystemTimeSlotClock,
-        CachingEth1Backend<E, HotColdDB<E>>,
+        CachingEth1Backend<E>,
         E,
         TeeEventHandler<E>,
+        LevelDB<E>,
+        LevelDB<E>,
     >,
 >;
 

beacon_node/store/Cargo.toml

@@ -29,3 +29,4 @@ serde_derive = "1.0.110"
 lazy_static = "1.4.0"
 lighthouse_metrics = { path = "../../common/lighthouse_metrics" }
 lru = "0.5.1"
+sloggers = "1.0.0"

beacon_node/store/src/chunked_iter.rs

@@ -1,5 +1,5 @@
 use crate::chunked_vector::{chunk_key, Chunk, Field};
-use crate::HotColdDB;
+use crate::{HotColdDB, ItemStore};
 use slog::error;
 use std::sync::Arc;
 use types::{ChainSpec, EthSpec, Slot};
@@ -7,22 +7,26 @@ use types::{ChainSpec, EthSpec, Slot};
 /// Iterator over the values of a `BeaconState` vector field (like `block_roots`).
 ///
 /// Uses the freezer DB's separate table to load the values.
-pub struct ChunkedVectorIter<F, E>
+pub struct ChunkedVectorIter<F, E, Hot, Cold>
 where
     F: Field<E>,
     E: EthSpec,
+    Hot: ItemStore<E>,
+    Cold: ItemStore<E>,
 {
-    pub(crate) store: Arc<HotColdDB<E>>,
+    pub(crate) store: Arc<HotColdDB<E, Hot, Cold>>,
     current_vindex: usize,
     pub(crate) end_vindex: usize,
     next_cindex: usize,
     current_chunk: Chunk<F::Value>,
 }
 
-impl<F, E> ChunkedVectorIter<F, E>
+impl<F, E, Hot, Cold> ChunkedVectorIter<F, E, Hot, Cold>
 where
     F: Field<E>,
     E: EthSpec,
+    Hot: ItemStore<E>,
+    Cold: ItemStore<E>,
 {
     /// Create a new iterator which can yield elements from `start_vindex` up to the last
     /// index stored by the restore point at `last_restore_point_slot`.
@@ -31,7 +35,7 @@ where
     /// `HotColdDB::get_latest_restore_point_slot`. We pass it as a parameter so that the caller can
     /// maintain a stable view of the database (see `HybridForwardsBlockRootsIterator`).
     pub fn new(
-        store: Arc<HotColdDB<E>>,
+        store: Arc<HotColdDB<E, Hot, Cold>>,
         start_vindex: usize,
         last_restore_point_slot: Slot,
         spec: &ChainSpec,
@@ -53,10 +57,12 @@ where
     }
 }
 
-impl<F, E> Iterator for ChunkedVectorIter<F, E>
+impl<F, E, Hot, Cold> Iterator for ChunkedVectorIter<F, E, Hot, Cold>
 where
     F: Field<E>,
     E: EthSpec,
+    Hot: ItemStore<E>,
+    Cold: ItemStore<E>,
 {
     type Item = (usize, F::Value);
 

beacon_node/store/src/forwards_iter.rs

@@ -2,14 +2,14 @@ use crate::chunked_iter::ChunkedVectorIter;
 use crate::chunked_vector::BlockRoots;
 use crate::errors::{Error, Result};
 use crate::iter::BlockRootsIterator;
-use crate::{HotColdDB, Store};
+use crate::{HotColdDB, ItemStore};
 use itertools::process_results;
 use std::sync::Arc;
 use types::{BeaconState, ChainSpec, EthSpec, Hash256, Slot};
 
 /// Forwards block roots iterator that makes use of the `block_roots` table in the freezer DB.
-pub struct FrozenForwardsBlockRootsIterator<E: EthSpec> {
+pub struct FrozenForwardsBlockRootsIterator<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
-    inner: ChunkedVectorIter<BlockRoots, E>,
+    inner: ChunkedVectorIter<BlockRoots, E, Hot, Cold>,
 }
 
 /// Forwards block roots iterator that reverses a backwards iterator (only good for short ranges).
@@ -19,9 +19,9 @@ pub struct SimpleForwardsBlockRootsIterator {
 }
 
 /// Fusion of the above two approaches to forwards iteration. Fast and efficient.
-pub enum HybridForwardsBlockRootsIterator<E: EthSpec> {
+pub enum HybridForwardsBlockRootsIterator<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
     PreFinalization {
-        iter: Box<FrozenForwardsBlockRootsIterator<E>>,
+        iter: Box<FrozenForwardsBlockRootsIterator<E, Hot, Cold>>,
         /// Data required by the `PostFinalization` iterator when we get to it.
         continuation_data: Box<Option<(BeaconState<E>, Hash256)>>,
     },
@@ -30,9 +30,11 @@ pub enum HybridForwardsBlockRootsIterator<E: EthSpec> {
     },
 }
 
-impl<E: EthSpec> FrozenForwardsBlockRootsIterator<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>
+    FrozenForwardsBlockRootsIterator<E, Hot, Cold>
+{
     pub fn new(
-        store: Arc<HotColdDB<E>>,
+        store: Arc<HotColdDB<E, Hot, Cold>>,
         start_slot: Slot,
         last_restore_point_slot: Slot,
         spec: &ChainSpec,
@@ -48,7 +50,9 @@ impl<E: EthSpec> FrozenForwardsBlockRootsIterator<E> {
     }
 }
 
-impl<E: EthSpec> Iterator for FrozenForwardsBlockRootsIterator<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> Iterator
+    for FrozenForwardsBlockRootsIterator<E, Hot, Cold>
+{
     type Item = (Hash256, Slot);
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -59,8 +63,8 @@ impl<E: EthSpec> Iterator for FrozenForwardsBlockRootsIterator<E> {
 }
 
 impl SimpleForwardsBlockRootsIterator {
-    pub fn new<S: Store<E>, E: EthSpec>(
+    pub fn new<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>(
-        store: Arc<S>,
+        store: Arc<HotColdDB<E, Hot, Cold>>,
         start_slot: Slot,
         end_state: BeaconState<E>,
         end_block_root: Hash256,
@@ -87,9 +91,11 @@ impl Iterator for SimpleForwardsBlockRootsIterator {
     }
 }
 
-impl<E: EthSpec> HybridForwardsBlockRootsIterator<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>
+    HybridForwardsBlockRootsIterator<E, Hot, Cold>
+{
     pub fn new(
-        store: Arc<HotColdDB<E>>,
+        store: Arc<HotColdDB<E, Hot, Cold>>,
         start_slot: Slot,
         end_state: BeaconState<E>,
         end_block_root: Hash256,
@@ -157,7 +163,9 @@ impl<E: EthSpec> HybridForwardsBlockRootsIterator<E> {
     }
 }
 
-impl<E: EthSpec> Iterator for HybridForwardsBlockRootsIterator<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> Iterator
+    for HybridForwardsBlockRootsIterator<E, Hot, Cold>
+{
     type Item = Result<(Hash256, Slot)>;
 
     fn next(&mut self) -> Option<Self::Item> {

beacon_node/store/src/hot_cold_store.rs

@@ -5,10 +5,12 @@ use crate::config::StoreConfig;
 use crate::forwards_iter::HybridForwardsBlockRootsIterator;
 use crate::impls::beacon_state::{get_full_state, store_full_state};
 use crate::iter::{ParentRootBlockIterator, StateRootsIterator};
+use crate::leveldb_store::LevelDB;
+use crate::memory_store::MemoryStore;
 use crate::metrics;
 use crate::{
-    leveldb_store::LevelDB, DBColumn, Error, ItemStore, KeyValueStore, PartialBeaconState, Store,
+    get_key_for_col, DBColumn, Error, ItemStore, KeyValueStoreOp, PartialBeaconState, StoreItem,
-    StoreItem, StoreOp,
+    StoreOp,
 };
 use lru::LruCache;
 use parking_lot::{Mutex, RwLock};
@@ -32,7 +34,7 @@ pub const SPLIT_DB_KEY: &str = "FREEZERDBSPLITFREEZERDBSPLITFREE";
 ///
 /// Stores vector fields like the `block_roots` and `state_roots` separately, and only stores
 /// intermittent "restore point" states pre-finalization.
-pub struct HotColdDB<E: EthSpec> {
+pub struct HotColdDB<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
     /// The slot and state root at the point where the database is split between hot and cold.
     ///
     /// States with slots less than `split.slot` are in the cold DB, while states with slots
@@ -40,11 +42,11 @@ pub struct HotColdDB<E: EthSpec> {
     split: RwLock<Split>,
     config: StoreConfig,
     /// Cold database containing compact historical data.
-    pub(crate) cold_db: LevelDB<E>,
+    pub(crate) cold_db: Cold,
     /// Hot database containing duplicated but quick-to-access recent data.
     ///
     /// The hot database also contains all blocks.
-    pub(crate) hot_db: LevelDB<E>,
+    pub(crate) hot_db: Hot,
     /// LRU cache of deserialized blocks. Updated whenever a block is loaded.
     block_cache: Mutex<LruCache<Hash256, SignedBeaconBlock<E>>>,
     /// Chain spec.
@@ -84,11 +86,13 @@ pub enum HotColdDBError {
     RestorePointBlockHashError(BeaconStateError),
 }
 
-impl<E: EthSpec> Store<E> for HotColdDB<E> {
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold> {
-    type ForwardsBlockRootsIterator = HybridForwardsBlockRootsIterator<E>;
-
     /// Store a block and update the LRU cache.
-    fn put_block(&self, block_root: &Hash256, block: SignedBeaconBlock<E>) -> Result<(), Error> {
+    pub fn put_block(
+        &self,
+        block_root: &Hash256,
+        block: SignedBeaconBlock<E>,
+    ) -> Result<(), Error> {
         // Store on disk.
         self.hot_db.put(block_root, &block)?;
 
@@ -99,7 +103,7 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
     }
 
     /// Fetch a block from the store.
-    fn get_block(&self, block_root: &Hash256) -> Result<Option<SignedBeaconBlock<E>>, Error> {
+    pub fn get_block(&self, block_root: &Hash256) -> Result<Option<SignedBeaconBlock<E>>, Error> {
         metrics::inc_counter(&metrics::BEACON_BLOCK_GET_COUNT);
 
         // Check the cache.
@@ -120,12 +124,12 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
     }
 
     /// Delete a block from the store and the block cache.
-    fn delete_block(&self, block_root: &Hash256) -> Result<(), Error> {
+    pub fn delete_block(&self, block_root: &Hash256) -> Result<(), Error> {
         self.block_cache.lock().pop(block_root);
         self.hot_db.delete::<SignedBeaconBlock<E>>(block_root)
     }
 
-    fn put_state_summary(
+    pub fn put_state_summary(
         &self,
         state_root: &Hash256,
         summary: HotStateSummary,
@@ -134,7 +138,7 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
     }
 
     /// Store a state in the store.
-    fn put_state(&self, state_root: &Hash256, state: &BeaconState<E>) -> Result<(), Error> {
+    pub fn put_state(&self, state_root: &Hash256, state: &BeaconState<E>) -> Result<(), Error> {
         if state.slot < self.get_split_slot() {
             self.store_cold_state(state_root, &state)
         } else {
@@ -143,7 +147,7 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
     }
 
     /// Fetch a state from the store.
-    fn get_state(
+    pub fn get_state(
         &self,
         state_root: &Hash256,
         slot: Option<Slot>,
@@ -170,7 +174,7 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
     /// than the split point. You shouldn't delete states from the finalized portion of the chain
     /// (which are frozen, and won't be deleted), or valid descendents of the finalized checkpoint
     /// (which will be deleted by this function but shouldn't be).
-    fn delete_state(&self, state_root: &Hash256, slot: Slot) -> Result<(), Error> {
+    pub fn delete_state(&self, state_root: &Hash256, slot: Slot) -> Result<(), Error> {
         // Delete the state summary.
         self.hot_db
             .key_delete(DBColumn::BeaconStateSummary.into(), state_root.as_bytes())?;
@@ -184,20 +188,20 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
         Ok(())
     }
 
-    fn forwards_block_roots_iterator(
+    pub fn forwards_block_roots_iterator(
         store: Arc<Self>,
         start_slot: Slot,
         end_state: BeaconState<E>,
         end_block_root: Hash256,
         spec: &ChainSpec,
-    ) -> Result<Self::ForwardsBlockRootsIterator, Error> {
+    ) -> Result<impl Iterator<Item = Result<(Hash256, Slot), Error>>, Error> {
         HybridForwardsBlockRootsIterator::new(store, start_slot, end_state, end_block_root, spec)
     }
 
     /// Load an epoch boundary state by using the hot state summary look-up.
     ///
     /// Will fall back to the cold DB if a hot state summary is not found.
-    fn load_epoch_boundary_state(
+    pub fn load_epoch_boundary_state(
         &self,
         state_root: &Hash256,
     ) -> Result<Option<BeaconState<E>>, Error> {
@@ -226,21 +230,49 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
         }
     }
 
-    fn put_item<I: StoreItem>(&self, key: &Hash256, item: &I) -> Result<(), Error> {
+    pub fn put_item<I: StoreItem>(&self, key: &Hash256, item: &I) -> Result<(), Error> {
         self.hot_db.put(key, item)
     }
 
-    fn get_item<I: StoreItem>(&self, key: &Hash256) -> Result<Option<I>, Error> {
+    pub fn get_item<I: StoreItem>(&self, key: &Hash256) -> Result<Option<I>, Error> {
         self.hot_db.get(key)
     }
 
-    fn item_exists<I: StoreItem>(&self, key: &Hash256) -> Result<bool, Error> {
+    pub fn item_exists<I: StoreItem>(&self, key: &Hash256) -> Result<bool, Error> {
         self.hot_db.exists::<I>(key)
     }
 
-    fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error> {
+    pub fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error> {
         let mut guard = self.block_cache.lock();
-        self.hot_db.do_atomically(batch)?;
+
+        let mut key_value_batch: Vec<KeyValueStoreOp> = Vec::with_capacity(batch.len());
+        for op in batch {
+            match op {
+                StoreOp::DeleteBlock(block_hash) => {
+                    let untyped_hash: Hash256 = (*block_hash).into();
+                    let key =
+                        get_key_for_col(DBColumn::BeaconBlock.into(), untyped_hash.as_bytes());
+                    key_value_batch.push(KeyValueStoreOp::DeleteKey(key));
+                }
+
+                StoreOp::DeleteState(state_hash, slot) => {
+                    let untyped_hash: Hash256 = (*state_hash).into();
+                    let state_summary_key = get_key_for_col(
+                        DBColumn::BeaconStateSummary.into(),
+                        untyped_hash.as_bytes(),
+                    );
+                    key_value_batch.push(KeyValueStoreOp::DeleteKey(state_summary_key));
+
+                    if *slot % E::slots_per_epoch() == 0 {
+                        let state_key =
+                            get_key_for_col(DBColumn::BeaconState.into(), untyped_hash.as_bytes());
+                        key_value_batch.push(KeyValueStoreOp::DeleteKey(state_key));
+                    }
+                }
+            }
+        }
+        self.hot_db.do_atomically(&key_value_batch)?;
+
         for op in batch {
             match op {
                 StoreOp::DeleteBlock(block_hash) => {
@@ -254,7 +286,30 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
     }
 }
 
-impl<E: EthSpec> HotColdDB<E> {
+impl<E: EthSpec> HotColdDB<E, MemoryStore<E>, MemoryStore<E>> {
+    pub fn open_ephemeral(
+        config: StoreConfig,
+        spec: ChainSpec,
+        log: Logger,
+    ) -> Result<HotColdDB<E, MemoryStore<E>, MemoryStore<E>>, Error> {
+        Self::verify_slots_per_restore_point(config.slots_per_restore_point)?;
+
+        let db = HotColdDB {
+            split: RwLock::new(Split::default()),
+            cold_db: MemoryStore::open(),
+            hot_db: MemoryStore::open(),
+            block_cache: Mutex::new(LruCache::new(config.block_cache_size)),
+            config,
+            spec,
+            log,
+            _phantom: PhantomData,
+        };
+
+        Ok(db)
+    }
+}
+
+impl<E: EthSpec> HotColdDB<E, LevelDB<E>, LevelDB<E>> {
     /// Open a new or existing database, with the given paths to the hot and cold DBs.
     ///
     /// The `slots_per_restore_point` parameter must be a divisor of `SLOTS_PER_HISTORICAL_ROOT`.
@@ -264,7 +319,7 @@ impl<E: EthSpec> HotColdDB<E> {
         config: StoreConfig,
         spec: ChainSpec,
         log: Logger,
-    ) -> Result<Self, Error> {
+    ) -> Result<HotColdDB<E, LevelDB<E>, LevelDB<E>>, Error> {
         Self::verify_slots_per_restore_point(config.slots_per_restore_point)?;
 
         let db = HotColdDB {
@@ -285,7 +340,9 @@ impl<E: EthSpec> HotColdDB<E> {
         }
         Ok(db)
     }
+}
 
+impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold> {
     /// Store a post-finalization state efficiently in the hot database.
     ///
     /// On an epoch boundary, store a full state. On an intermediate slot, store
@@ -675,8 +732,8 @@ impl<E: EthSpec> HotColdDB<E> {
 }
 
 /// Advance the split point of the store, moving new finalized states to the freezer.
-pub fn process_finalization<E: EthSpec>(
+pub fn process_finalization<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>(
-    store: Arc<HotColdDB<E>>,
+    store: Arc<HotColdDB<E, Hot, Cold>>,
     frozen_head_root: Hash256,
     frozen_head: &BeaconState<E>,
 ) -> Result<(), Error> {

beacon_node/store/src/iter.rs

@@ -1,4 +1,4 @@
-use crate::{Error, Store};
+use crate::{Error, HotColdDB, ItemStore};
 use std::borrow::Cow;
 use std::marker::PhantomData;
 use std::sync::Arc;
@@ -12,17 +12,20 @@ use types::{
 ///
 /// It is assumed that all ancestors for this object are stored in the database. If this is not the
 /// case, the iterator will start returning `None` prior to genesis.
-pub trait AncestorIter<U: Store<E>, E: EthSpec, I: Iterator> {
+pub trait AncestorIter<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>, I: Iterator> {
     /// Returns an iterator over the roots of the ancestors of `self`.
-    fn try_iter_ancestor_roots(&self, store: Arc<U>) -> Option<I>;
+    fn try_iter_ancestor_roots(&self, store: Arc<HotColdDB<E, Hot, Cold>>) -> Option<I>;
 }
 
-impl<'a, U: Store<E>, E: EthSpec> AncestorIter<U, E, BlockRootsIterator<'a, E, U>>
+impl<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>
-    for SignedBeaconBlock<E>
+    AncestorIter<E, Hot, Cold, BlockRootsIterator<'a, E, Hot, Cold>> for SignedBeaconBlock<E>
 {
     /// Iterates across all available prior block roots of `self`, starting at the most recent and ending
     /// at genesis.
-    fn try_iter_ancestor_roots(&self, store: Arc<U>) -> Option<BlockRootsIterator<'a, E, U>> {
+    fn try_iter_ancestor_roots(
+        &self,
+        store: Arc<HotColdDB<E, Hot, Cold>>,
+    ) -> Option<BlockRootsIterator<'a, E, Hot, Cold>> {
         let state = store
             .get_state(&self.message.state_root, Some(self.message.slot))
             .ok()??;
@@ -31,22 +34,27 @@ impl<'a, U: Store<E>, E: EthSpec> AncestorIter<U, E, BlockRootsIterator<'a, E, U
     }
 }
 
-impl<'a, U: Store<E>, E: EthSpec> AncestorIter<U, E, StateRootsIterator<'a, E, U>>
+impl<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>
-    for BeaconState<E>
+    AncestorIter<E, Hot, Cold, StateRootsIterator<'a, E, Hot, Cold>> for BeaconState<E>
 {
     /// Iterates across all available prior state roots of `self`, starting at the most recent and ending
     /// at genesis.
-    fn try_iter_ancestor_roots(&self, store: Arc<U>) -> Option<StateRootsIterator<'a, E, U>> {
+    fn try_iter_ancestor_roots(
+        &self,
+        store: Arc<HotColdDB<E, Hot, Cold>>,
+    ) -> Option<StateRootsIterator<'a, E, Hot, Cold>> {
         // The `self.clone()` here is wasteful.
         Some(StateRootsIterator::owned(store, self.clone()))
     }
 }
 
-pub struct StateRootsIterator<'a, T: EthSpec, U: Store<T>> {
+pub struct StateRootsIterator<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> {
-    inner: RootsIterator<'a, T, U>,
+    inner: RootsIterator<'a, T, Hot, Cold>,
 }
 
-impl<'a, T: EthSpec, U: Store<T>> Clone for StateRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> Clone
+    for StateRootsIterator<'a, T, Hot, Cold>
+{
     fn clone(&self) -> Self {
         Self {
             inner: self.inner.clone(),
@@ -54,21 +62,23 @@ impl<'a, T: EthSpec, U: Store<T>> Clone for StateRootsIterator<'a, T, U> {
     }
 }
 
-impl<'a, T: EthSpec, U: Store<T>> StateRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> StateRootsIterator<'a, T, Hot, Cold> {
-    pub fn new(store: Arc<U>, beacon_state: &'a BeaconState<T>) -> Self {
+    pub fn new(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: &'a BeaconState<T>) -> Self {
         Self {
             inner: RootsIterator::new(store, beacon_state),
         }
     }
 
-    pub fn owned(store: Arc<U>, beacon_state: BeaconState<T>) -> Self {
+    pub fn owned(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: BeaconState<T>) -> Self {
         Self {
             inner: RootsIterator::owned(store, beacon_state),
         }
     }
 }
 
-impl<'a, T: EthSpec, U: Store<T>> Iterator for StateRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> Iterator
+    for StateRootsIterator<'a, T, Hot, Cold>
+{
     type Item = Result<(Hash256, Slot), Error>;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -86,11 +96,13 @@ impl<'a, T: EthSpec, U: Store<T>> Iterator for StateRootsIterator<'a, T, U> {
 /// exhausted.
 ///
 /// Returns `None` for roots prior to genesis or when there is an error reading from `Store`.
-pub struct BlockRootsIterator<'a, T: EthSpec, U: Store<T>> {
+pub struct BlockRootsIterator<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> {
-    inner: RootsIterator<'a, T, U>,
+    inner: RootsIterator<'a, T, Hot, Cold>,
 }
 
-impl<'a, T: EthSpec, U: Store<T>> Clone for BlockRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> Clone
+    for BlockRootsIterator<'a, T, Hot, Cold>
+{
     fn clone(&self) -> Self {
         Self {
             inner: self.inner.clone(),
@@ -98,23 +110,25 @@ impl<'a, T: EthSpec, U: Store<T>> Clone for BlockRootsIterator<'a, T, U> {
     }
 }
 
-impl<'a, T: EthSpec, U: Store<T>> BlockRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> BlockRootsIterator<'a, T, Hot, Cold> {
     /// Create a new iterator over all block roots in the given `beacon_state` and prior states.
-    pub fn new(store: Arc<U>, beacon_state: &'a BeaconState<T>) -> Self {
+    pub fn new(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: &'a BeaconState<T>) -> Self {
         Self {
             inner: RootsIterator::new(store, beacon_state),
         }
     }
 
     /// Create a new iterator over all block roots in the given `beacon_state` and prior states.
-    pub fn owned(store: Arc<U>, beacon_state: BeaconState<T>) -> Self {
+    pub fn owned(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: BeaconState<T>) -> Self {
         Self {
             inner: RootsIterator::owned(store, beacon_state),
         }
     }
 }
 
-impl<'a, T: EthSpec, U: Store<T>> Iterator for BlockRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> Iterator
+    for BlockRootsIterator<'a, T, Hot, Cold>
+{
     type Item = Result<(Hash256, Slot), Error>;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -125,13 +139,15 @@ impl<'a, T: EthSpec, U: Store<T>> Iterator for BlockRootsIterator<'a, T, U> {
 }
 
 /// Iterator over state and block roots that backtracks using the vectors from a `BeaconState`.
-pub struct RootsIterator<'a, T: EthSpec, U: Store<T>> {
+pub struct RootsIterator<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> {
-    store: Arc<U>,
+    store: Arc<HotColdDB<T, Hot, Cold>>,
     beacon_state: Cow<'a, BeaconState<T>>,
     slot: Slot,
 }
 
-impl<'a, T: EthSpec, U: Store<T>> Clone for RootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> Clone
+    for RootsIterator<'a, T, Hot, Cold>
+{
     fn clone(&self) -> Self {
         Self {
             store: self.store.clone(),
@@ -141,8 +157,8 @@ impl<'a, T: EthSpec, U: Store<T>> Clone for RootsIterator<'a, T, U> {
     }
 }
 
-impl<'a, T: EthSpec, U: Store<T>> RootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> RootsIterator<'a, T, Hot, Cold> {
-    pub fn new(store: Arc<U>, beacon_state: &'a BeaconState<T>) -> Self {
+    pub fn new(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: &'a BeaconState<T>) -> Self {
         Self {
             store,
             slot: beacon_state.slot,
@@ -150,7 +166,7 @@ impl<'a, T: EthSpec, U: Store<T>> RootsIterator<'a, T, U> {
         }
     }
 
-    pub fn owned(store: Arc<U>, beacon_state: BeaconState<T>) -> Self {
+    pub fn owned(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: BeaconState<T>) -> Self {
         Self {
             store,
             slot: beacon_state.slot,
@@ -158,7 +174,10 @@ impl<'a, T: EthSpec, U: Store<T>> RootsIterator<'a, T, U> {
         }
     }
 
-    pub fn from_block(store: Arc<U>, block_hash: Hash256) -> Result<Self, Error> {
+    pub fn from_block(
+        store: Arc<HotColdDB<T, Hot, Cold>>,
+        block_hash: Hash256,
+    ) -> Result<Self, Error> {
         let block = store
             .get_block(&block_hash)?
             .ok_or_else(|| BeaconStateError::MissingBeaconBlock(block_hash.into()))?;
@@ -198,7 +217,9 @@ impl<'a, T: EthSpec, U: Store<T>> RootsIterator<'a, T, U> {
     }
 }
 
-impl<'a, T: EthSpec, U: Store<T>> Iterator for RootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> Iterator
+    for RootsIterator<'a, T, Hot, Cold>
+{
     /// (block_root, state_root, slot)
     type Item = Result<(Hash256, Hash256, Slot), Error>;
 
@@ -208,14 +229,16 @@ impl<'a, T: EthSpec, U: Store<T>> Iterator for RootsIterator<'a, T, U> {
 }
 
 /// Block iterator that uses the `parent_root` of each block to backtrack.
-pub struct ParentRootBlockIterator<'a, E: EthSpec, S: Store<E>> {
+pub struct ParentRootBlockIterator<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
-    store: &'a S,
+    store: &'a HotColdDB<E, Hot, Cold>,
     next_block_root: Hash256,
     _phantom: PhantomData<E>,
 }
 
-impl<'a, E: EthSpec, S: Store<E>> ParentRootBlockIterator<'a, E, S> {
+impl<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>
-    pub fn new(store: &'a S, start_block_root: Hash256) -> Self {
+    ParentRootBlockIterator<'a, E, Hot, Cold>
+{
+    pub fn new(store: &'a HotColdDB<E, Hot, Cold>, start_block_root: Hash256) -> Self {
         Self {
             store,
             next_block_root: start_block_root,
@@ -240,7 +263,9 @@ impl<'a, E: EthSpec, S: Store<E>> ParentRootBlockIterator<'a, E, S> {
     }
 }
 
-impl<'a, E: EthSpec, S: Store<E>> Iterator for ParentRootBlockIterator<'a, E, S> {
+impl<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> Iterator
+    for ParentRootBlockIterator<'a, E, Hot, Cold>
+{
     type Item = Result<(Hash256, SignedBeaconBlock<E>), Error>;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -250,20 +275,20 @@ impl<'a, E: EthSpec, S: Store<E>> Iterator for ParentRootBlockIterator<'a, E, S>
 
 #[derive(Clone)]
 /// Extends `BlockRootsIterator`, returning `SignedBeaconBlock` instances, instead of their roots.
-pub struct BlockIterator<'a, T: EthSpec, U: Store<T>> {
+pub struct BlockIterator<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> {
-    roots: BlockRootsIterator<'a, T, U>,
+    roots: BlockRootsIterator<'a, T, Hot, Cold>,
 }
 
-impl<'a, T: EthSpec, U: Store<T>> BlockIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> BlockIterator<'a, T, Hot, Cold> {
     /// Create a new iterator over all blocks in the given `beacon_state` and prior states.
-    pub fn new(store: Arc<U>, beacon_state: &'a BeaconState<T>) -> Self {
+    pub fn new(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: &'a BeaconState<T>) -> Self {
         Self {
             roots: BlockRootsIterator::new(store, beacon_state),
         }
     }
 
     /// Create a new iterator over all blocks in the given `beacon_state` and prior states.
-    pub fn owned(store: Arc<U>, beacon_state: BeaconState<T>) -> Self {
+    pub fn owned(store: Arc<HotColdDB<T, Hot, Cold>>, beacon_state: BeaconState<T>) -> Self {
         Self {
             roots: BlockRootsIterator::owned(store, beacon_state),
         }
@@ -279,7 +304,9 @@ impl<'a, T: EthSpec, U: Store<T>> BlockIterator<'a, T, U> {
     }
 }
 
-impl<'a, T: EthSpec, U: Store<T>> Iterator for BlockIterator<'a, T, U> {
+impl<'a, T: EthSpec, Hot: ItemStore<T>, Cold: ItemStore<T>> Iterator
+    for BlockIterator<'a, T, Hot, Cold>
+{
     type Item = Result<SignedBeaconBlock<T>, Error>;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -288,8 +315,8 @@ impl<'a, T: EthSpec, U: Store<T>> Iterator for BlockIterator<'a, T, U> {
 }
 
 /// Fetch the next state to use whilst backtracking in `*RootsIterator`.
-fn next_historical_root_backtrack_state<E: EthSpec, S: Store<E>>(
+fn next_historical_root_backtrack_state<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>>(
-    store: &S,
+    store: &HotColdDB<E, Hot, Cold>,
     current_state: &BeaconState<E>,
 ) -> Result<BeaconState<E>, Error> {
     // For compatibility with the freezer database's restore points, we load a state at
@@ -312,8 +339,10 @@ fn slot_of_prev_restore_point<E: EthSpec>(current_slot: Slot) -> Slot {
 #[cfg(test)]
 mod test {
     use super::*;
-    use crate::MemoryStore;
+    use crate::config::StoreConfig;
-    use types::{test_utils::TestingBeaconStateBuilder, Keypair, MainnetEthSpec};
+    use crate::HotColdDB;
+    use sloggers::{null::NullLoggerBuilder, Build};
+    use types::{test_utils::TestingBeaconStateBuilder, ChainSpec, Keypair, MainnetEthSpec};
 
     fn get_state<T: EthSpec>() -> BeaconState<T> {
         let builder = TestingBeaconStateBuilder::from_single_keypair(
@@ -327,7 +356,10 @@ mod test {
 
     #[test]
     fn block_root_iter() {
-        let store = Arc::new(MemoryStore::open());
+        let log = NullLoggerBuilder.build().unwrap();
+        let store = Arc::new(
+            HotColdDB::open_ephemeral(StoreConfig::default(), ChainSpec::minimal(), log).unwrap(),
+        );
         let slots_per_historical_root = MainnetEthSpec::slots_per_historical_root();
 
         let mut state_a: BeaconState<MainnetEthSpec> = get_state();
@@ -371,7 +403,10 @@ mod test {
 
     #[test]
     fn state_root_iter() {
-        let store = Arc::new(MemoryStore::open());
+        let log = NullLoggerBuilder.build().unwrap();
+        let store = Arc::new(
+            HotColdDB::open_ephemeral(StoreConfig::default(), ChainSpec::minimal(), log).unwrap(),
+        );
         let slots_per_historical_root = MainnetEthSpec::slots_per_historical_root();
 
         let mut state_a: BeaconState<MainnetEthSpec> = get_state();

beacon_node/store/src/leveldb_store.rs

@@ -48,7 +48,7 @@ impl<E: EthSpec> KeyValueStore<E> for LevelDB<E> {
         let timer = metrics::start_timer(&metrics::DISK_DB_READ_TIMES);
 
         self.db
-            .get(self.read_options(), column_key)
+            .get(self.read_options(), BytesKey::from_vec(column_key))
             .map_err(Into::into)
             .map(|opt| {
                 opt.map(|bytes| {
@@ -68,7 +68,7 @@ impl<E: EthSpec> KeyValueStore<E> for LevelDB<E> {
         let timer = metrics::start_timer(&metrics::DISK_DB_WRITE_TIMES);
 
         self.db
-            .put(self.write_options(), column_key, val)
+            .put(self.write_options(), BytesKey::from_vec(column_key), val)
             .map_err(Into::into)
             .map(|()| {
                 metrics::stop_timer(timer);
@@ -82,7 +82,7 @@ impl<E: EthSpec> KeyValueStore<E> for LevelDB<E> {
         metrics::inc_counter(&metrics::DISK_DB_EXISTS_COUNT);
 
         self.db
-            .get(self.read_options(), column_key)
+            .get(self.read_options(), BytesKey::from_vec(column_key))
             .map_err(Into::into)
             .and_then(|val| Ok(val.is_some()))
     }
@@ -94,34 +94,16 @@ impl<E: EthSpec> KeyValueStore<E> for LevelDB<E> {
         metrics::inc_counter(&metrics::DISK_DB_DELETE_COUNT);
 
         self.db
-            .delete(self.write_options(), column_key)
+            .delete(self.write_options(), BytesKey::from_vec(column_key))
             .map_err(Into::into)
     }
 
-    fn do_atomically(&self, ops_batch: &[StoreOp]) -> Result<(), Error> {
+    fn do_atomically(&self, ops_batch: &[KeyValueStoreOp]) -> Result<(), Error> {
         let mut leveldb_batch = Writebatch::new();
-        for op in ops_batch {
+        for op in ops_batch.into_iter() {
             match op {
-                StoreOp::DeleteBlock(block_hash) => {
+                KeyValueStoreOp::DeleteKey(key) => {
-                    let untyped_hash: Hash256 = (*block_hash).into();
+                    leveldb_batch.delete(BytesKey::from_vec(key.to_vec()));
-                    let key =
-                        get_key_for_col(DBColumn::BeaconBlock.into(), untyped_hash.as_bytes());
-                    leveldb_batch.delete(key);
-                }
-
-                StoreOp::DeleteState(state_hash, slot) => {
-                    let untyped_hash: Hash256 = (*state_hash).into();
-                    let state_summary_key = get_key_for_col(
-                        DBColumn::BeaconStateSummary.into(),
-                        untyped_hash.as_bytes(),
-                    );
-                    leveldb_batch.delete(state_summary_key);
-
-                    if *slot % E::slots_per_epoch() == 0 {
-                        let state_key =
-                            get_key_for_col(DBColumn::BeaconState.into(), untyped_hash.as_bytes());
-                        leveldb_batch.delete(state_key);
-                    }
                 }
             }
         }
@@ -147,10 +129,10 @@ impl Key for BytesKey {
     }
 }
 
-fn get_key_for_col(col: &str, key: &[u8]) -> BytesKey {
+impl BytesKey {
-    let mut col = col.as_bytes().to_vec();
+    fn from_vec(key: Vec<u8>) -> Self {
-    col.append(&mut key.to_vec());
+        Self { key }
-    BytesKey { key: col }
+    }
 }
 
 impl From<LevelDBError> for Error {

beacon_node/store/src/lib.rs

@@ -25,8 +25,6 @@ mod state_batch;
 
 pub mod iter;
 
-use std::sync::Arc;
-
 pub use self::config::StoreConfig;
 pub use self::hot_cold_store::{HotColdDB, HotStateSummary};
 pub use self::leveldb_store::LevelDB;
@@ -52,7 +50,17 @@ pub trait KeyValueStore<E: EthSpec>: Sync + Send + Sized + 'static {
     fn key_delete(&self, column: &str, key: &[u8]) -> Result<(), Error>;
 
     /// Execute either all of the operations in `batch` or none at all, returning an error.
-    fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error>;
+    fn do_atomically(&self, batch: &[KeyValueStoreOp]) -> Result<(), Error>;
+}
+
+pub fn get_key_for_col(column: &str, key: &[u8]) -> Vec<u8> {
+    let mut result = column.as_bytes().to_vec();
+    result.extend_from_slice(key);
+    result
+}
+
+pub enum KeyValueStoreOp {
+    DeleteKey(Vec<u8>),
 }
 
 pub trait ItemStore<E: EthSpec>: KeyValueStore<E> + Sync + Send + Sized + 'static {
@@ -93,75 +101,6 @@ pub trait ItemStore<E: EthSpec>: KeyValueStore<E> + Sync + Send + Sized + 'stati
     }
 }
 
-/// An object capable of storing and retrieving objects implementing `StoreItem`.
-///
-/// A `Store` is fundamentally backed by a key-value database, however it provides support for
-/// columns. A simple column implementation might involve prefixing a key with some bytes unique to
-/// each column.
-pub trait Store<E: EthSpec>: Sync + Send + Sized + 'static {
-    type ForwardsBlockRootsIterator: Iterator<Item = Result<(Hash256, Slot), Error>>;
-
-    /// Store a block in the store.
-    fn put_block(&self, block_root: &Hash256, block: SignedBeaconBlock<E>) -> Result<(), Error>;
-
-    /// Fetch a block from the store.
-    fn get_block(&self, block_root: &Hash256) -> Result<Option<SignedBeaconBlock<E>>, Error>;
-
-    /// Delete a block from the store.
-    fn delete_block(&self, block_root: &Hash256) -> Result<(), Error>;
-
-    /// Store a state in the store.
-    fn put_state(&self, state_root: &Hash256, state: &BeaconState<E>) -> Result<(), Error>;
-
-    /// Store a state summary in the store.
-    fn put_state_summary(
-        &self,
-        state_root: &Hash256,
-        summary: HotStateSummary,
-    ) -> Result<(), Error>;
-
-    /// Fetch a state from the store.
-    fn get_state(
-        &self,
-        state_root: &Hash256,
-        slot: Option<Slot>,
-    ) -> Result<Option<BeaconState<E>>, Error>;
-
-    /// Delete a state from the store.
-    fn delete_state(&self, state_root: &Hash256, _slot: Slot) -> Result<(), Error>;
-
-    /// Get a forwards (slot-ascending) iterator over the beacon block roots since `start_slot`.
-    ///
-    /// Will be efficient for frozen portions of the database if using `HotColdDB`.
-    ///
-    /// The `end_state` and `end_block_root` are required for backtracking in the post-finalization
-    /// part of the chain, and should be usually be set to the current head. Importantly, the
-    /// `end_state` must be a state that has had a block applied to it, and the hash of that
-    /// block must be `end_block_root`.
-    // NOTE: could maybe optimise by getting the `BeaconState` and end block root from a closure, as
-    // it's not always required.
-    fn forwards_block_roots_iterator(
-        store: Arc<Self>,
-        start_slot: Slot,
-        end_state: BeaconState<E>,
-        end_block_root: Hash256,
-        spec: &ChainSpec,
-    ) -> Result<Self::ForwardsBlockRootsIterator, Error>;
-
-    fn load_epoch_boundary_state(
-        &self,
-        state_root: &Hash256,
-    ) -> Result<Option<BeaconState<E>>, Error>;
-
-    fn put_item<I: StoreItem>(&self, key: &Hash256, item: &I) -> Result<(), Error>;
-
-    fn get_item<I: StoreItem>(&self, key: &Hash256) -> Result<Option<I>, Error>;
-
-    fn item_exists<I: StoreItem>(&self, key: &Hash256) -> Result<bool, Error>;
-
-    fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error>;
-}
-
 /// Reified key-value storage operation.  Helps in modifying the storage atomically.
 /// See also https://github.com/sigp/lighthouse/issues/692
 pub enum StoreOp {

beacon_node/store/src/memory_store.rs

@@ -1,12 +1,7 @@
-use super::{DBColumn, Error, ItemStore, KeyValueStore, Store, StoreOp};
+use super::{Error, ItemStore, KeyValueStore, KeyValueStoreOp};
-use crate::forwards_iter::SimpleForwardsBlockRootsIterator;
-use crate::hot_cold_store::HotStateSummary;
-use crate::impls::beacon_state::{get_full_state, store_full_state};
-use crate::StoreItem;
 use parking_lot::RwLock;
 use std::collections::HashMap;
 use std::marker::PhantomData;
-use std::sync::Arc;
 use types::*;
 
 type DBHashMap = HashMap<Vec<u8>, Vec<u8>>;
@@ -46,53 +41,34 @@ impl<E: EthSpec> KeyValueStore<E> for MemoryStore<E> {
     /// Get the value of some key from the database. Returns `None` if the key does not exist.
     fn get_bytes(&self, col: &str, key: &[u8]) -> Result<Option<Vec<u8>>, Error> {
         let column_key = Self::get_key_for_col(col, key);
-
         Ok(self.db.read().get(&column_key).cloned())
     }
 
     /// Puts a key in the database.
     fn put_bytes(&self, col: &str, key: &[u8], val: &[u8]) -> Result<(), Error> {
         let column_key = Self::get_key_for_col(col, key);
-
         self.db.write().insert(column_key, val.to_vec());
-
         Ok(())
     }
 
     /// Return true if some key exists in some column.
     fn key_exists(&self, col: &str, key: &[u8]) -> Result<bool, Error> {
         let column_key = Self::get_key_for_col(col, key);
-
         Ok(self.db.read().contains_key(&column_key))
     }
 
     /// Delete some key from the database.
     fn key_delete(&self, col: &str, key: &[u8]) -> Result<(), Error> {
         let column_key = Self::get_key_for_col(col, key);
-
         self.db.write().remove(&column_key);
-
         Ok(())
     }
 
-    fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error> {
+    fn do_atomically(&self, batch: &[KeyValueStoreOp]) -> Result<(), Error> {
         for op in batch {
             match op {
-                StoreOp::DeleteBlock(block_hash) => {
+                KeyValueStoreOp::DeleteKey(hash) => {
-                    let untyped_hash: Hash256 = (*block_hash).into();
+                    self.db.write().remove(hash);
-                    self.key_delete(DBColumn::BeaconBlock.into(), untyped_hash.as_bytes())?;
-                }
-
-                StoreOp::DeleteState(state_hash, slot) => {
-                    let untyped_hash: Hash256 = (*state_hash).into();
-                    if *slot % E::slots_per_epoch() == 0 {
-                        self.key_delete(DBColumn::BeaconState.into(), untyped_hash.as_bytes())?;
-                    } else {
-                        self.key_delete(
-                            DBColumn::BeaconStateSummary.into(),
-                            untyped_hash.as_bytes(),
-                        )?;
-                    }
                 }
             }
         }
@@ -101,94 +77,3 @@ impl<E: EthSpec> KeyValueStore<E> for MemoryStore<E> {
 }
 
 impl<E: EthSpec> ItemStore<E> for MemoryStore<E> {}
-
-impl<E: EthSpec> Store<E> for MemoryStore<E> {
-    type ForwardsBlockRootsIterator = SimpleForwardsBlockRootsIterator;
-
-    fn put_block(&self, block_root: &Hash256, block: SignedBeaconBlock<E>) -> Result<(), Error> {
-        self.put(block_root, &block)
-    }
-
-    fn get_block(&self, block_root: &Hash256) -> Result<Option<SignedBeaconBlock<E>>, Error> {
-        self.get(block_root)
-    }
-
-    fn delete_block(&self, block_root: &Hash256) -> Result<(), Error> {
-        self.key_delete(DBColumn::BeaconBlock.into(), block_root.as_bytes())
-    }
-
-    fn put_state_summary(
-        &self,
-        state_root: &Hash256,
-        summary: HotStateSummary,
-    ) -> Result<(), Error> {
-        self.put(state_root, &summary).map_err(Into::into)
-    }
-
-    /// Store a state in the store.
-    fn put_state(&self, state_root: &Hash256, state: &BeaconState<E>) -> Result<(), Error> {
-        store_full_state(self, state_root, &state)
-    }
-
-    /// Fetch a state from the store.
-    fn get_state(
-        &self,
-        state_root: &Hash256,
-        _: Option<Slot>,
-    ) -> Result<Option<BeaconState<E>>, Error> {
-        get_full_state(self, state_root)
-    }
-
-    fn delete_state(&self, state_root: &Hash256, _slot: Slot) -> Result<(), Error> {
-        self.key_delete(DBColumn::BeaconState.into(), state_root.as_bytes())
-    }
-
-    fn forwards_block_roots_iterator(
-        store: Arc<Self>,
-        start_slot: Slot,
-        end_state: BeaconState<E>,
-        end_block_root: Hash256,
-        _: &ChainSpec,
-    ) -> Result<Self::ForwardsBlockRootsIterator, Error> {
-        SimpleForwardsBlockRootsIterator::new(store, start_slot, end_state, end_block_root)
-    }
-
-    /// Load the most recent ancestor state of `state_root` which lies on an epoch boundary.
-    ///
-    /// If `state_root` corresponds to an epoch boundary state, then that state itself should be
-    /// returned.
-    fn load_epoch_boundary_state(
-        &self,
-        state_root: &Hash256,
-    ) -> Result<Option<BeaconState<E>>, Error> {
-        // The default implementation is not very efficient, but isn't used in prod.
-        // See `HotColdDB` for the optimized implementation.
-        if let Some(state) = self.get_state(state_root, None)? {
-            let epoch_boundary_slot = state.slot / E::slots_per_epoch() * E::slots_per_epoch();
-            if state.slot == epoch_boundary_slot {
-                Ok(Some(state))
-            } else {
-                let epoch_boundary_state_root = state.get_state_root(epoch_boundary_slot)?;
-                self.get_state(epoch_boundary_state_root, Some(epoch_boundary_slot))
-            }
-        } else {
-            Ok(None)
-        }
-    }
-
-    fn put_item<I: StoreItem>(&self, key: &Hash256, item: &I) -> Result<(), Error> {
-        self.put(key, item)
-    }
-
-    fn get_item<I: StoreItem>(&self, key: &Hash256) -> Result<Option<I>, Error> {
-        self.get(key)
-    }
-
-    fn item_exists<I: StoreItem>(&self, key: &Hash256) -> Result<bool, Error> {
-        self.exists::<I>(key)
-    }
-
-    fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error> {
-        KeyValueStore::do_atomically(self, batch)
-    }
-}

beacon_node/store/src/state_batch.rs

@@ -1,4 +1,4 @@
-use crate::{Error, HotStateSummary, Store};
+use crate::{Error, HotColdDB, HotStateSummary, ItemStore};
 use types::{BeaconState, EthSpec, Hash256};
 
 /// A collection of states to be stored in the database.
@@ -36,7 +36,10 @@ impl<E: EthSpec> StateBatch<E> {
     /// Write the batch to the database.
     ///
     /// May fail to write the full batch if any of the items error (i.e. not atomic!)
-    pub fn commit<S: Store<E>>(self, store: &S) -> Result<(), Error> {
+    pub fn commit<Hot: ItemStore<E>, Cold: ItemStore<E>>(
+        self,
+        store: &HotColdDB<E, Hot, Cold>,
+    ) -> Result<(), Error> {
         self.items.into_iter().try_for_each(|item| match item {
             BatchItem::Full(state_root, state) => store.put_state(&state_root, &state),
             BatchItem::Summary(state_root, summary) => {