Clean up database abstractions (#1200)

* Remove redundant method

* Pull out a method out of a struct

* More precise db access abstractions

* Move fake trait method out of it

* cargo fmt

* Fix compilation error after refactoring

* Move another fake method out the Store trait

* Get rid of superfluous method

* Fix refactoring bug

* Rename: SimpleStoreItem -> StoreItem

* Get rid of the confusing DiskStore type alias

* Get rid of SimpleDiskStore type alias

* Correction: A method took both self and a ref to Self

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -151,7 +151,7 @@ pub struct HeadInfo {
 
 pub trait BeaconChainTypes: Send + Sync + 'static {
     type Store: store::Store<Self::EthSpec>;
-    type StoreMigrator: Migrate<Self::Store, Self::EthSpec>;
+    type StoreMigrator: Migrate<Self::EthSpec>;
     type SlotClock: slot_clock::SlotClock;
     type Eth1Chain: Eth1ChainBackend<Self::EthSpec, Self::Store>;
     type EthSpec: types::EthSpec;
@@ -241,7 +241,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
 
         let fork_choice_timer = metrics::start_timer(&metrics::PERSIST_FORK_CHOICE);
 
-        self.store.put(
+        self.store.put_item(
             &Hash256::from_slice(&FORK_CHOICE_DB_KEY),
             &self.fork_choice.as_ssz_container(),
         )?;
@@ -250,7 +250,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         let head_timer = metrics::start_timer(&metrics::PERSIST_HEAD);
 
         self.store
-            .put(&Hash256::from_slice(&BEACON_CHAIN_DB_KEY), &persisted_head)?;
+            .put_item(&Hash256::from_slice(&BEACON_CHAIN_DB_KEY), &persisted_head)?;
 
         metrics::stop_timer(head_timer);
 
@@ -266,7 +266,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     pub fn persist_op_pool(&self) -> Result<(), Error> {
         let timer = metrics::start_timer(&metrics::PERSIST_OP_POOL);
 
-        self.store.put(
+        self.store.put_item(
             &Hash256::from_slice(&OP_POOL_DB_KEY),
             &PersistedOperationPool::from_operation_pool(&self.op_pool),
         )?;
@@ -281,7 +281,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         let timer = metrics::start_timer(&metrics::PERSIST_OP_POOL);
 
         if let Some(eth1_chain) = self.eth1_chain.as_ref() {
-            self.store.put(
+            self.store.put_item(
                 &Hash256::from_slice(&ETH1_CACHE_DB_KEY),
                 &eth1_chain.as_ssz_container(),
             )?;
@@ -426,7 +426,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             .map(|(root, _)| root);
 
         if let Some(block_root) = root {
-            Ok(self.store.get(&block_root)?)
+            Ok(self.store.get_item(&block_root)?)
         } else {
             Ok(None)
         }
@@ -1934,7 +1934,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     pub fn is_new_block_root(&self, beacon_block_root: &Hash256) -> Result<bool, Error> {
         Ok(!self
             .store
-            .exists::<SignedBeaconBlock<T::EthSpec>>(beacon_block_root)?)
+            .item_exists::<SignedBeaconBlock<T::EthSpec>>(beacon_block_root)?)
     }
 
     /// Dumps the entire canonical chain, from the head to genesis to a vector for analysis.

beacon_node/beacon_chain/src/builder.rs

@@ -48,7 +48,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     for Witness<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec> + 'static,
     TSlotClock: SlotClock + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
@@ -98,7 +98,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec> + 'static,
     TSlotClock: SlotClock + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
@@ -184,7 +184,7 @@ where
             .ok_or_else(|| "get_persisted_eth1_backend requires a store.".to_string())?;
 
         store
-            .get::<SszEth1>(&Hash256::from_slice(&ETH1_CACHE_DB_KEY))
+            .get_item::<SszEth1>(&Hash256::from_slice(&ETH1_CACHE_DB_KEY))
             .map_err(|e| format!("DB error whilst reading eth1 cache: {:?}", e))
     }
 
@@ -196,7 +196,7 @@ where
             .ok_or_else(|| "store_contains_beacon_chain requires a store.".to_string())?;
 
         Ok(store
-            .get::<PersistedBeaconChain>(&Hash256::from_slice(&BEACON_CHAIN_DB_KEY))
+            .get_item::<PersistedBeaconChain>(&Hash256::from_slice(&BEACON_CHAIN_DB_KEY))
             .map_err(|e| format!("DB error when reading persisted beacon chain: {:?}", e))?
             .is_some())
     }
@@ -227,7 +227,7 @@ where
             .ok_or_else(|| "resume_from_db requires a store.".to_string())?;
 
         let chain = store
-            .get::<PersistedBeaconChain>(&Hash256::from_slice(&BEACON_CHAIN_DB_KEY))
+            .get_item::<PersistedBeaconChain>(&Hash256::from_slice(&BEACON_CHAIN_DB_KEY))
             .map_err(|e| format!("DB error when reading persisted beacon chain: {:?}", e))?
             .ok_or_else(|| {
                 "No persisted beacon chain found in store. Try purging the beacon chain database."
@@ -242,7 +242,7 @@ where
 
         let head_block_root = chain.canonical_head_block_root;
         let head_block = store
-            .get::<SignedBeaconBlock<TEthSpec>>(&head_block_root)
+            .get_item::<SignedBeaconBlock<TEthSpec>>(&head_block_root)
             .map_err(|e| format!("DB error when reading head block: {:?}", e))?
             .ok_or_else(|| "Head block not found in store".to_string())?;
         let head_state_root = head_block.state_root();
@@ -253,7 +253,7 @@ where
 
         self.op_pool = Some(
             store
-                .get::<PersistedOperationPool<TEthSpec>>(&Hash256::from_slice(&OP_POOL_DB_KEY))
+                .get_item::<PersistedOperationPool<TEthSpec>>(&Hash256::from_slice(&OP_POOL_DB_KEY))
                 .map_err(|e| format!("DB error whilst reading persisted op pool: {:?}", e))?
                 .map(|persisted| persisted.into_operation_pool(&head_state, &self.spec))
                 .unwrap_or_else(|| OperationPool::new()),
@@ -261,7 +261,7 @@ where
 
         let finalized_block_root = head_state.finalized_checkpoint.root;
         let finalized_block = store
-            .get::<SignedBeaconBlock<TEthSpec>>(&finalized_block_root)
+            .get_item::<SignedBeaconBlock<TEthSpec>>(&finalized_block_root)
             .map_err(|e| format!("DB error when reading finalized block: {:?}", e))?
             .ok_or_else(|| "Finalized block not found in store".to_string())?;
         let finalized_state_root = finalized_block.state_root();
@@ -317,11 +317,13 @@ where
             .put_state(&beacon_state_root, &beacon_state)
             .map_err(|e| format!("Failed to store genesis state: {:?}", e))?;
         store
-            .put(&beacon_block_root, &beacon_block)
+            .put_item(&beacon_block_root, &beacon_block)
             .map_err(|e| format!("Failed to store genesis block: {:?}", e))?;
 
         // Store the genesis block under the `ZERO_HASH` key.
-        store.put(&Hash256::zero(), &beacon_block).map_err(|e| {
+        store
+            .put_item(&Hash256::zero(), &beacon_block)
+            .map_err(|e| {
                 format!(
                     "Failed to store genesis block under 0x00..00 alias: {:?}",
                     e
@@ -484,7 +486,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec> + 'static,
     TSlotClock: SlotClock + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
@@ -501,7 +503,7 @@ where
             .ok_or_else(|| "reduced_tree_fork_choice requires a store.".to_string())?;
 
         let persisted_fork_choice = store
-            .get::<SszForkChoice>(&Hash256::from_slice(&FORK_CHOICE_DB_KEY))
+            .get_item::<SszForkChoice>(&Hash256::from_slice(&FORK_CHOICE_DB_KEY))
             .map_err(|e| format!("DB error when reading persisted fork choice: {:?}", e))?;
 
         let fork_choice = if let Some(persisted) = persisted_fork_choice {
@@ -554,7 +556,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec> + 'static,
     TSlotClock: SlotClock + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
@@ -592,7 +594,7 @@ impl<TStore, TStoreMigrator, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec> + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
@@ -631,7 +633,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec> + 'static,
     TSlotClock: SlotClock + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,

beacon_node/beacon_chain/src/eth1_chain.rs

@@ -10,7 +10,7 @@ use std::collections::HashMap;
 use std::iter::DoubleEndedIterator;
 use std::marker::PhantomData;
 use std::sync::Arc;
-use store::{DBColumn, Error as StoreError, SimpleStoreItem, Store};
+use store::{DBColumn, Error as StoreError, Store, StoreItem};
 use types::{
     BeaconState, BeaconStateError, ChainSpec, Deposit, Eth1Data, EthSpec, Hash256, Slot, Unsigned,
     DEPOSIT_TREE_DEPTH,
@@ -59,7 +59,7 @@ pub struct SszEth1 {
     backend_bytes: Vec<u8>,
 }
 
-impl SimpleStoreItem for SszEth1 {
+impl StoreItem for SszEth1 {
     fn db_column() -> DBColumn {
         DBColumn::Eth1Cache
     }

beacon_node/beacon_chain/src/fork_choice.rs

@@ -8,7 +8,7 @@ use ssz::{Decode, Encode};
 use ssz_derive::{Decode, Encode};
 use state_processing::common::get_indexed_attestation;
 use std::marker::PhantomData;
-use store::{DBColumn, Error as StoreError, SimpleStoreItem};
+use store::{DBColumn, Error as StoreError, StoreItem};
 use types::{BeaconBlock, BeaconState, BeaconStateError, Epoch, Hash256, IndexedAttestation, Slot};
 
 type Result<T> = std::result::Result<T, Error>;
@@ -285,7 +285,7 @@ impl From<String> for Error {
     }
 }
 
-impl SimpleStoreItem for SszForkChoice {
+impl StoreItem for SszForkChoice {
     fn db_column() -> DBColumn {
         DBColumn::ForkChoice
     }

beacon_node/beacon_chain/src/migrate.rs

@@ -7,15 +7,16 @@ use std::mem;
 use std::sync::mpsc;
 use std::sync::Arc;
 use std::thread;
+use store::hot_cold_store::{process_finalization, HotColdDBError};
 use store::iter::{ParentRootBlockIterator, RootsIterator};
-use store::{hot_cold_store::HotColdDBError, Error, SimpleDiskStore, Store, StoreOp};
+use store::{Error, Store, StoreOp};
-pub use store::{DiskStore, MemoryStore};
+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<S: Store<E>, E: EthSpec>: Send + Sync + 'static {
+pub trait Migrate<E: EthSpec>: Send + Sync + 'static {
-    fn new(db: Arc<S>, log: Logger) -> Self;
+    fn new(db: Arc<HotColdDB<E>>, log: Logger) -> Self;
 
     fn process_finalization(
         &self,
@@ -35,7 +36,7 @@ pub trait Migrate<S: Store<E>, E: EthSpec>: Send + Sync + 'static {
     /// Assumptions:
     ///  * It is called after every finalization.
     fn prune_abandoned_forks(
-        store: Arc<S>,
+        store: Arc<HotColdDB<E>>,
         head_tracker: Arc<HeadTracker>,
         old_finalized_block_hash: SignedBeaconBlockHash,
         new_finalized_block_hash: SignedBeaconBlockHash,
@@ -164,14 +165,8 @@ pub trait Migrate<S: Store<E>, E: EthSpec>: Send + Sync + 'static {
 /// Migrator that does nothing, for stores that don't need migration.
 pub struct NullMigrator;
 
-impl<E: EthSpec> Migrate<SimpleDiskStore<E>, E> for NullMigrator {
+impl<E: EthSpec> Migrate<E> for NullMigrator {
-    fn new(_: Arc<SimpleDiskStore<E>>, _: Logger) -> Self {
+    fn new(_: Arc<HotColdDB<E>>, _: Logger) -> Self {
-        NullMigrator
-    }
-}
-
-impl<E: EthSpec> Migrate<MemoryStore<E>, E> for NullMigrator {
-    fn new(_: Arc<MemoryStore<E>>, _: Logger) -> Self {
         NullMigrator
     }
 }
@@ -179,12 +174,12 @@ impl<E: EthSpec> Migrate<MemoryStore<E>, E> for NullMigrator {
 /// Migrator that immediately calls the store's migration function, blocking the current execution.
 ///
 /// Mostly useful for tests.
-pub struct BlockingMigrator<S> {
+pub struct BlockingMigrator<E: EthSpec> {
-    db: Arc<S>,
+    db: Arc<HotColdDB<E>>,
 }
 
-impl<E: EthSpec, S: Store<E>> Migrate<S, E> for BlockingMigrator<S> {
+impl<E: EthSpec> Migrate<E> for BlockingMigrator<E> {
-    fn new(db: Arc<S>, _: Logger) -> Self {
+    fn new(db: Arc<HotColdDB<E>>, _: Logger) -> Self {
         BlockingMigrator { db }
     }
 
@@ -197,7 +192,7 @@ impl<E: EthSpec, S: Store<E>> Migrate<S, E> for BlockingMigrator<S> {
         old_finalized_block_hash: SignedBeaconBlockHash,
         new_finalized_block_hash: SignedBeaconBlockHash,
     ) {
-        if let Err(e) = S::process_finalization(self.db.clone(), state_root, &new_finalized_state) {
+        if let Err(e) = process_finalization(self.db.clone(), state_root, &new_finalized_state) {
             // This migrator is only used for testing, so we just log to stderr without a logger.
             eprintln!("Migration error: {:?}", e);
         }
@@ -225,13 +220,13 @@ 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> {
-    db: Arc<DiskStore<E>>,
+    db: Arc<HotColdDB<E>>,
     tx_thread: Mutex<(MpscSender<E>, thread::JoinHandle<()>)>,
     log: Logger,
 }
 
-impl<E: EthSpec> Migrate<DiskStore<E>, E> for BackgroundMigrator<E> {
+impl<E: EthSpec> Migrate<E> for BackgroundMigrator<E> {
-    fn new(db: Arc<DiskStore<E>>, log: Logger) -> Self {
+    fn new(db: Arc<HotColdDB<E>>, log: Logger) -> Self {
         let tx_thread = Mutex::new(Self::spawn_thread(db.clone(), log.clone()));
         Self { db, tx_thread, log }
     }
@@ -293,7 +288,7 @@ impl<E: EthSpec> BackgroundMigrator<E> {
     ///
     /// Return a channel handle for sending new finalized states to the thread.
     fn spawn_thread(
-        db: Arc<DiskStore<E>>,
+        db: Arc<HotColdDB<E>>,
         log: Logger,
     ) -> (
         mpsc::Sender<(
@@ -317,7 +312,7 @@ impl<E: EthSpec> BackgroundMigrator<E> {
                 new_finalized_slot,
             )) = rx.recv()
             {
-                match DiskStore::process_finalization(db.clone(), state_root, &state) {
+                match process_finalization(db.clone(), state_root, &state) {
                     Ok(()) => {}
                     Err(Error::HotColdDBError(HotColdDBError::FreezeSlotUnaligned(slot))) => {
                         debug!(

beacon_node/beacon_chain/src/persisted_beacon_chain.rs

@@ -1,7 +1,7 @@
 use crate::head_tracker::SszHeadTracker;
 use ssz::{Decode, Encode};
 use ssz_derive::{Decode, Encode};
-use store::{DBColumn, Error as StoreError, SimpleStoreItem};
+use store::{DBColumn, Error as StoreError, StoreItem};
 use types::Hash256;
 
 #[derive(Clone, Encode, Decode)]
@@ -11,7 +11,7 @@ pub struct PersistedBeaconChain {
     pub ssz_head_tracker: SszHeadTracker,
 }
 
-impl SimpleStoreItem for PersistedBeaconChain {
+impl StoreItem for PersistedBeaconChain {
     fn db_column() -> DBColumn {
         DBColumn::BeaconChain
     }

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::{DiskStore, MemoryStore, Store};
+use store::{HotColdDB, MemoryStore, Store};
 use tempfile::{tempdir, TempDir};
 use tree_hash::TreeHash;
 use types::{
@@ -44,7 +44,7 @@ pub type BaseHarnessType<TStore, TStoreMigrator, TEthSpec> = Witness<
 >;
 
 pub type HarnessType<E> = BaseHarnessType<MemoryStore<E>, NullMigrator, E>;
-pub type DiskHarnessType<E> = BaseHarnessType<DiskStore<E>, BlockingMigrator<DiskStore<E>>, E>;
+pub type DiskHarnessType<E> = BaseHarnessType<HotColdDB<E>, BlockingMigrator<E>, E>;
 
 /// Indicates how the `BeaconChainHarness` should produce blocks.
 #[derive(Clone, Copy, Debug)]
@@ -140,7 +140,7 @@ 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<DiskStore<E>>,
+        store: Arc<HotColdDB<E>>,
         keypairs: Vec<Keypair>,
     ) -> Self {
         let data_dir = tempdir().expect("should create temporary data_dir");
@@ -152,10 +152,7 @@ impl<E: EthSpec> BeaconChainHarness<DiskHarnessType<E>> {
             .logger(log.clone())
             .custom_spec(spec.clone())
             .store(store.clone())
-            .store_migrator(<BlockingMigrator<_> as Migrate<_, E>>::new(
+            .store_migrator(BlockingMigrator::new(store, log.clone()))
-                store,
-                log.clone(),
-            ))
             .data_dir(data_dir.path().to_path_buf())
             .genesis_state(
                 interop_genesis_state::<E>(&keypairs, HARNESS_GENESIS_TIME, &spec)
@@ -183,7 +180,7 @@ 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<DiskStore<E>>,
+        store: Arc<HotColdDB<E>>,
         keypairs: Vec<Keypair>,
         data_dir: TempDir,
     ) -> Self {
@@ -195,10 +192,7 @@ impl<E: EthSpec> BeaconChainHarness<DiskHarnessType<E>> {
             .logger(log.clone())
             .custom_spec(spec)
             .store(store.clone())
-            .store_migrator(<BlockingMigrator<_> as Migrate<_, E>>::new(
+            .store_migrator(<BlockingMigrator<_> as Migrate<E>>::new(store, log.clone()))
-                store,
-                log.clone(),
-            ))
             .data_dir(data_dir.path().to_path_buf())
             .resume_from_db()
             .expect("should resume beacon chain from db")
@@ -224,7 +218,7 @@ impl<E: EthSpec> BeaconChainHarness<DiskHarnessType<E>> {
 impl<S, M, E> BeaconChainHarness<BaseHarnessType<S, M, E>>
 where
     S: Store<E>,
-    M: Migrate<S, E>,
+    M: Migrate<E>,
     E: EthSpec,
 {
     /// Advance the slot of the `BeaconChain`.

beacon_node/beacon_chain/tests/attestation_verification.rs

@@ -988,7 +988,7 @@ fn attestation_that_skips_epochs() {
     let block_slot = harness
         .chain
         .store
-        .get::<SignedBeaconBlock<E>>(&block_root)
+        .get_item::<SignedBeaconBlock<E>>(&block_root)
         .expect("should not error getting block")
         .expect("should find attestation block")
         .message

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::{DiskStore, StoreConfig};
+use store::{HotColdDB, StoreConfig};
 use tempfile::{tempdir, TempDir};
 use types::{EthSpec, Keypair, MinimalEthSpec};
 
@@ -23,14 +23,14 @@ lazy_static! {
     static ref KEYPAIRS: Vec<Keypair> = types::test_utils::generate_deterministic_keypairs(VALIDATOR_COUNT);
 }
 
-fn get_store(db_path: &TempDir) -> Arc<DiskStore<E>> {
+fn get_store(db_path: &TempDir) -> Arc<HotColdDB<E>> {
     let spec = E::default_spec();
     let hot_path = db_path.path().join("hot_db");
     let cold_path = db_path.path().join("cold_db");
     let config = StoreConfig::default();
     let log = NullLoggerBuilder.build().expect("logger should build");
     Arc::new(
-        DiskStore::open(&hot_path, &cold_path, config, spec, log)
+        HotColdDB::open(&hot_path, &cold_path, config, spec, log)
             .expect("disk store should initialize"),
     )
 }

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},
-    DiskStore, Store, StoreConfig,
+    HotColdDB, Store, StoreConfig,
 };
 use tempfile::{tempdir, TempDir};
 use tree_hash::TreeHash;
@@ -35,19 +35,19 @@ lazy_static! {
 type E = MinimalEthSpec;
 type TestHarness = BeaconChainHarness<DiskHarnessType<E>>;
 
-fn get_store(db_path: &TempDir) -> Arc<DiskStore<E>> {
+fn get_store(db_path: &TempDir) -> Arc<HotColdDB<E>> {
     let spec = MinimalEthSpec::default_spec();
     let hot_path = db_path.path().join("hot_db");
     let cold_path = db_path.path().join("cold_db");
     let config = StoreConfig::default();
     let log = NullLoggerBuilder.build().expect("logger should build");
     Arc::new(
-        DiskStore::open(&hot_path, &cold_path, config, spec, log)
+        HotColdDB::open(&hot_path, &cold_path, config, spec, log)
             .expect("disk store should initialize"),
     )
 }
 
-fn get_harness(store: Arc<DiskStore<E>>, validator_count: usize) -> TestHarness {
+fn get_harness(store: Arc<HotColdDB<E>>, validator_count: usize) -> TestHarness {
     let harness = BeaconChainHarness::new_with_disk_store(
         MinimalEthSpec,
         store,
@@ -1305,8 +1305,8 @@ fn check_finalization(harness: &TestHarness, expected_slot: u64) {
     );
 }
 
-/// Check that the DiskStore's split_slot is equal to the start slot of the last finalized epoch.
+/// 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<DiskStore<E>>) {
+fn check_split_slot(harness: &TestHarness, store: Arc<HotColdDB<E>>) {
     let split_slot = store.get_split_slot();
     assert_eq!(
         harness

beacon_node/beacon_chain/tests/tests.rs

@@ -354,7 +354,7 @@ fn roundtrip_operation_pool() {
     let restored_op_pool = harness
         .chain
         .store
-        .get::<PersistedOperationPool<MinimalEthSpec>>(&key)
+        .get_item::<PersistedOperationPool<MinimalEthSpec>>(&key)
         .expect("should read db")
         .expect("should find op pool")
         .into_operation_pool(&head_state, &harness.spec);

beacon_node/client/src/builder.rs

@@ -6,7 +6,7 @@ use beacon_chain::{
     eth1_chain::{CachingEth1Backend, Eth1Chain},
     migrate::{BackgroundMigrator, Migrate, NullMigrator},
     slot_clock::{SlotClock, SystemTimeSlotClock},
-    store::{DiskStore, MemoryStore, SimpleDiskStore, Store, StoreConfig},
+    store::{HotColdDB, MemoryStore, Store, StoreConfig},
     BeaconChain, BeaconChainTypes, Eth1ChainBackend, EventHandler,
 };
 use environment::RuntimeContext;
@@ -65,7 +65,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec>,
+    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + Clone + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
@@ -376,7 +376,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec>,
+    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + Clone + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
@@ -423,7 +423,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec>,
+    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + 'static,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
@@ -462,7 +462,7 @@ where
 impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     ClientBuilder<
         Witness<
-            DiskStore<TEthSpec>,
+            HotColdDB<TEthSpec>,
             TStoreMigrator,
             TSlotClock,
             TEth1Backend,
@@ -472,12 +472,12 @@ impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TSlotClock: SlotClock + 'static,
-    TStoreMigrator: Migrate<DiskStore<TEthSpec>, TEthSpec> + 'static,
+    TStoreMigrator: Migrate<TEthSpec> + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, DiskStore<TEthSpec>> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec, HotColdDB<TEthSpec>> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
 {
-    /// Specifies that the `Client` should use a `DiskStore` database.
+    /// Specifies that the `Client` should use a `HotColdDB` database.
     pub fn disk_store(
         mut self,
         hot_path: &Path,
@@ -494,40 +494,13 @@ where
             .clone()
             .ok_or_else(|| "disk_store requires a chain spec".to_string())?;
 
-        let store = DiskStore::open(hot_path, cold_path, config, spec, context.log)
+        let store = HotColdDB::open(hot_path, cold_path, config, spec, context.log)
             .map_err(|e| format!("Unable to open database: {:?}", e))?;
         self.store = Some(Arc::new(store));
         Ok(self)
     }
 }
 
-impl<TStoreMigrator, TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
-    ClientBuilder<
-        Witness<
-            SimpleDiskStore<TEthSpec>,
-            TStoreMigrator,
-            TSlotClock,
-            TEth1Backend,
-            TEthSpec,
-            TEventHandler,
-        >,
-    >
-where
-    TSlotClock: SlotClock + 'static,
-    TStoreMigrator: Migrate<SimpleDiskStore<TEthSpec>, TEthSpec> + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, SimpleDiskStore<TEthSpec>> + 'static,
-    TEthSpec: EthSpec + 'static,
-    TEventHandler: EventHandler<TEthSpec> + 'static,
-{
-    /// Specifies that the `Client` should use a `DiskStore` database.
-    pub fn simple_disk_store(mut self, path: &Path) -> Result<Self, String> {
-        let store =
-            SimpleDiskStore::open(path).map_err(|e| format!("Unable to open database: {:?}", e))?;
-        self.store = Some(Arc::new(store));
-        Ok(self)
-    }
-}
-
 impl<TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     ClientBuilder<
         Witness<
@@ -559,7 +532,7 @@ where
 impl<TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     ClientBuilder<
         Witness<
-            DiskStore<TEthSpec>,
+            HotColdDB<TEthSpec>,
             BackgroundMigrator<TEthSpec>,
             TSlotClock,
             TEth1Backend,
@@ -569,7 +542,7 @@ impl<TSlotClock, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TSlotClock: SlotClock + 'static,
-    TEth1Backend: Eth1ChainBackend<TEthSpec, DiskStore<TEthSpec>> + 'static,
+    TEth1Backend: Eth1ChainBackend<TEthSpec, HotColdDB<TEthSpec>> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
 {
@@ -600,7 +573,7 @@ impl<TStore, TStoreMigrator, TSlotClock, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec>,
+    TStoreMigrator: Migrate<TEthSpec>,
     TSlotClock: SlotClock + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,
@@ -706,7 +679,7 @@ impl<TStore, TStoreMigrator, TEth1Backend, TEthSpec, TEventHandler>
     >
 where
     TStore: Store<TEthSpec> + 'static,
-    TStoreMigrator: Migrate<TStore, TEthSpec>,
+    TStoreMigrator: Migrate<TEthSpec>,
     TEth1Backend: Eth1ChainBackend<TEthSpec, TStore> + 'static,
     TEthSpec: EthSpec + 'static,
     TEventHandler: EventHandler<TEthSpec> + 'static,

beacon_node/network/src/persisted_dht.rs

@@ -1,7 +1,7 @@
 use eth2_libp2p::Enr;
 use rlp;
 use std::sync::Arc;
-use store::{DBColumn, Error as StoreError, SimpleStoreItem, Store};
+use store::{DBColumn, Error as StoreError, Store, StoreItem};
 use types::{EthSpec, Hash256};
 
 /// 32-byte key for accessing the `DhtEnrs`.
@@ -10,7 +10,7 @@ pub const DHT_DB_KEY: &str = "PERSISTEDDHTPERSISTEDDHTPERSISTE";
 pub fn load_dht<T: Store<E>, E: EthSpec>(store: Arc<T>) -> Vec<Enr> {
     // Load DHT from store
     let key = Hash256::from_slice(&DHT_DB_KEY.as_bytes());
-    match store.get(&key) {
+    match store.get_item(&key) {
         Ok(Some(p)) => {
             let p: PersistedDht = p;
             p.enrs
@@ -25,7 +25,7 @@ pub fn persist_dht<T: Store<E>, E: EthSpec>(
     enrs: Vec<Enr>,
 ) -> Result<(), store::Error> {
     let key = Hash256::from_slice(&DHT_DB_KEY.as_bytes());
-    store.put(&key, &PersistedDht { enrs })?;
+    store.put_item(&key, &PersistedDht { enrs })?;
     Ok(())
 }
 
@@ -34,7 +34,7 @@ pub struct PersistedDht {
     pub enrs: Vec<Enr>,
 }
 
-impl SimpleStoreItem for PersistedDht {
+impl StoreItem for PersistedDht {
     fn db_column() -> DBColumn {
         DBColumn::DhtEnrs
     }
@@ -67,9 +67,9 @@ mod tests {
         let enrs = vec![Enr::from_str("enr:-IS4QHCYrYZbAKWCBRlAy5zzaDZXJBGkcnh4MHcBFZntXNFrdvJjX04jRzjzCBOonrkTfj499SZuOh8R33Ls8RRcy5wBgmlkgnY0gmlwhH8AAAGJc2VjcDI1NmsxoQPKY0yuDUmstAHYpMa2_oxVtw0RW_QAdpzBQA8yWM0xOIN1ZHCCdl8").unwrap()];
         let key = Hash256::from_slice(&DHT_DB_KEY.as_bytes());
         store
-            .put(&key, &PersistedDht { enrs: enrs.clone() })
+            .put_item(&key, &PersistedDht { enrs: enrs.clone() })
             .unwrap();
-        let dht: PersistedDht = store.get(&key).unwrap().unwrap();
+        let dht: PersistedDht = store.get_item(&key).unwrap().unwrap();
         assert_eq!(dht.enrs, enrs);
     }
 }

beacon_node/network/src/router/processor.rs

@@ -252,7 +252,7 @@ impl<T: BeaconChainTypes> Processor<T> {
         } else if self
             .chain
             .store
-            .exists::<SignedBeaconBlock<T::EthSpec>>(&remote.head_root)
+            .item_exists::<SignedBeaconBlock<T::EthSpec>>(&remote.head_root)
             .unwrap_or_else(|_| false)
         {
             debug!(

beacon_node/operation_pool/src/persistence.rs

@@ -4,7 +4,7 @@ use parking_lot::RwLock;
 use serde_derive::{Deserialize, Serialize};
 use ssz::{Decode, Encode};
 use ssz_derive::{Decode, Encode};
-use store::{DBColumn, Error as StoreError, SimpleStoreItem};
+use store::{DBColumn, Error as StoreError, StoreItem};
 use types::*;
 
 /// SSZ-serializable version of `OperationPool`.
@@ -102,7 +102,7 @@ impl<T: EthSpec> PersistedOperationPool<T> {
     }
 }
 
-impl<T: EthSpec> SimpleStoreItem for PersistedOperationPool<T> {
+impl<T: EthSpec> StoreItem for PersistedOperationPool<T> {
     fn db_column() -> DBColumn {
         DBColumn::OpPool
     }

beacon_node/src/lib.rs

@@ -10,7 +10,7 @@ pub use client::{Client, ClientBuilder, ClientConfig, ClientGenesis};
 pub use config::{get_data_dir, get_eth2_testnet_config, get_testnet_dir};
 pub use eth2_config::Eth2Config;
 
-use beacon_chain::migrate::{BackgroundMigrator, DiskStore};
+use beacon_chain::migrate::{BackgroundMigrator, HotColdDB};
 use beacon_chain::{
     builder::Witness, eth1_chain::CachingEth1Backend, events::WebSocketSender,
     slot_clock::SystemTimeSlotClock,
@@ -25,10 +25,10 @@ use types::EthSpec;
 /// A type-alias to the tighten the definition of a production-intended `Client`.
 pub type ProductionClient<E> = Client<
     Witness<
-        DiskStore<E>,
+        HotColdDB<E>,
         BackgroundMigrator<E>,
         SystemTimeSlotClock,
-        CachingEth1Backend<E, DiskStore<E>>,
+        CachingEth1Backend<E, HotColdDB<E>>,
         E,
         WebSocketSender<E>,
     >,

beacon_node/store/src/chunked_iter.rs

@@ -1,5 +1,5 @@
 use crate::chunked_vector::{chunk_key, Chunk, Field};
-use crate::DiskStore;
+use crate::HotColdDB;
 use slog::error;
 use std::sync::Arc;
 use types::{ChainSpec, EthSpec, Slot};
@@ -12,7 +12,7 @@ where
     F: Field<E>,
     E: EthSpec,
 {
-    pub(crate) store: Arc<DiskStore<E>>,
+    pub(crate) store: Arc<HotColdDB<E>>,
     current_vindex: usize,
     pub(crate) end_vindex: usize,
     next_cindex: usize,
@@ -28,10 +28,10 @@ where
     /// index stored by the restore point at `last_restore_point_slot`.
     ///
     /// The `last_restore_point` slot should be the slot of a recent restore point as obtained from
-    /// `DiskStore::get_latest_restore_point_slot`. We pass it as a parameter so that the caller can
+    /// `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<DiskStore<E>>,
+        store: Arc<HotColdDB<E>>,
         start_vindex: usize,
         last_restore_point_slot: Slot,
         spec: &ChainSpec,

beacon_node/store/src/chunked_vector.rs

@@ -177,7 +177,7 @@ pub trait Field<E: EthSpec>: Copy {
     /// Load the genesis value for a fixed length field from the store.
     ///
     /// This genesis value should be used to fill the initial state of the vector.
-    fn load_genesis_value<S: Store<E>>(store: &S) -> Result<Self::Value, Error> {
+    fn load_genesis_value<S: KeyValueStore<E>>(store: &S) -> Result<Self::Value, Error> {
         let key = &genesis_value_key()[..];
         let chunk =
             Chunk::load(store, Self::column(), key)?.ok_or(ChunkError::MissingGenesisValue)?;
@@ -192,7 +192,7 @@ pub trait Field<E: EthSpec>: Copy {
     ///
     /// Check the existing value (if any) for consistency with the value we intend to store, and
     /// return an error if they are inconsistent.
-    fn check_and_store_genesis_value<S: Store<E>>(
+    fn check_and_store_genesis_value<S: KeyValueStore<E>>(
         store: &S,
         value: Self::Value,
     ) -> Result<(), Error> {
@@ -327,7 +327,7 @@ field!(
     |state: &BeaconState<_>, index, _| safe_modulo_index(&state.randao_mixes, index)
 );
 
-pub fn store_updated_vector<F: Field<E>, E: EthSpec, S: Store<E>>(
+pub fn store_updated_vector<F: Field<E>, E: EthSpec, S: KeyValueStore<E>>(
     field: F,
     store: &S,
     state: &BeaconState<E>,
@@ -387,7 +387,7 @@ fn store_range<F, E, S, I>(
 where
     F: Field<E>,
     E: EthSpec,
-    S: Store<E>,
+    S: KeyValueStore<E>,
     I: Iterator<Item = usize>,
 {
     for chunk_index in range {
@@ -417,7 +417,7 @@ where
 
 // Chunks at the end index are included.
 // TODO: could be more efficient with a real range query (perhaps RocksDB)
-fn range_query<S: Store<E>, E: EthSpec, T: Decode + Encode>(
+fn range_query<S: KeyValueStore<E>, E: EthSpec, T: Decode + Encode>(
     store: &S,
     column: DBColumn,
     start_index: usize,
@@ -482,7 +482,7 @@ fn stitch<T: Default + Clone>(
     Ok(result)
 }
 
-pub fn load_vector_from_db<F: FixedLengthField<E>, E: EthSpec, S: Store<E>>(
+pub fn load_vector_from_db<F: FixedLengthField<E>, E: EthSpec, S: KeyValueStore<E>>(
     store: &S,
     slot: Slot,
     spec: &ChainSpec,
@@ -514,7 +514,7 @@ pub fn load_vector_from_db<F: FixedLengthField<E>, E: EthSpec, S: Store<E>>(
 }
 
 /// The historical roots are stored in vector chunks, despite not actually being a vector.
-pub fn load_variable_list_from_db<F: VariableLengthField<E>, E: EthSpec, S: Store<E>>(
+pub fn load_variable_list_from_db<F: VariableLengthField<E>, E: EthSpec, S: KeyValueStore<E>>(
     store: &S,
     slot: Slot,
     spec: &ChainSpec,
@@ -574,7 +574,7 @@ where
         Chunk { values }
     }
 
-    pub fn load<S: Store<E>, E: EthSpec>(
+    pub fn load<S: KeyValueStore<E>, E: EthSpec>(
         store: &S,
         column: DBColumn,
         key: &[u8],
@@ -585,7 +585,7 @@ where
             .transpose()
     }
 
-    pub fn store<S: Store<E>, E: EthSpec>(
+    pub fn store<S: KeyValueStore<E>, E: EthSpec>(
         &self,
         store: &S,
         column: DBColumn,

beacon_node/store/src/forwards_iter.rs

@@ -1,7 +1,7 @@
 use crate::chunked_iter::ChunkedVectorIter;
 use crate::chunked_vector::BlockRoots;
 use crate::iter::{BlockRootsIterator, ReverseBlockRootIterator};
-use crate::{DiskStore, Store};
+use crate::{HotColdDB, Store};
 use slog::error;
 use std::sync::Arc;
 use types::{BeaconState, ChainSpec, EthSpec, Hash256, Slot};
@@ -31,7 +31,7 @@ pub enum HybridForwardsBlockRootsIterator<E: EthSpec> {
 
 impl<E: EthSpec> FrozenForwardsBlockRootsIterator<E> {
     pub fn new(
-        store: Arc<DiskStore<E>>,
+        store: Arc<HotColdDB<E>>,
         start_slot: Slot,
         last_restore_point_slot: Slot,
         spec: &ChainSpec,
@@ -87,7 +87,7 @@ impl Iterator for SimpleForwardsBlockRootsIterator {
 
 impl<E: EthSpec> HybridForwardsBlockRootsIterator<E> {
     pub fn new(
-        store: Arc<DiskStore<E>>,
+        store: Arc<HotColdDB<E>>,
         start_slot: Slot,
         end_state: BeaconState<E>,
         end_block_root: Hash256,

beacon_node/store/src/hot_cold_store.rs

@@ -3,11 +3,12 @@ use crate::chunked_vector::{
 };
 use crate::config::StoreConfig;
 use crate::forwards_iter::HybridForwardsBlockRootsIterator;
-use crate::impls::beacon_state::store_full_state;
+use crate::impls::beacon_state::{get_full_state, store_full_state};
 use crate::iter::{ParentRootBlockIterator, StateRootsIterator};
 use crate::metrics;
 use crate::{
-    leveldb_store::LevelDB, DBColumn, Error, PartialBeaconState, SimpleStoreItem, Store, StoreOp,
+    leveldb_store::LevelDB, DBColumn, Error, ItemStore, KeyValueStore, PartialBeaconState, Store,
+    StoreItem, StoreOp,
 };
 use lru::LruCache;
 use parking_lot::{Mutex, RwLock};
@@ -86,27 +87,10 @@ pub enum HotColdDBError {
 impl<E: EthSpec> Store<E> for HotColdDB<E> {
     type ForwardsBlockRootsIterator = HybridForwardsBlockRootsIterator<E>;
 
-    // Defer to the hot database for basic operations (including blocks for now)
-    fn get_bytes(&self, column: &str, key: &[u8]) -> Result<Option<Vec<u8>>, Error> {
-        self.hot_db.get_bytes(column, key)
-    }
-
-    fn put_bytes(&self, column: &str, key: &[u8], value: &[u8]) -> Result<(), Error> {
-        self.hot_db.put_bytes(column, key, value)
-    }
-
-    fn key_exists(&self, column: &str, key: &[u8]) -> Result<bool, Error> {
-        self.hot_db.key_exists(column, key)
-    }
-
-    fn key_delete(&self, column: &str, key: &[u8]) -> Result<(), Error> {
-        self.hot_db.key_delete(column, key)
-    }
-
     /// Store a block and update the LRU cache.
     fn put_block(&self, block_root: &Hash256, block: SignedBeaconBlock<E>) -> Result<(), Error> {
         // Store on disk.
-        self.put(block_root, &block)?;
+        self.hot_db.put(block_root, &block)?;
 
         // Update cache.
         self.block_cache.lock().put(*block_root, block);
@@ -125,7 +109,7 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
         }
 
         // Fetch from database.
-        match self.get::<SignedBeaconBlock<E>>(block_root)? {
+        match self.hot_db.get::<SignedBeaconBlock<E>>(block_root)? {
             Some(block) => {
                 // Add to cache.
                 self.block_cache.lock().put(*block_root, block.clone());
@@ -138,7 +122,15 @@ 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> {
         self.block_cache.lock().pop(block_root);
-        self.delete::<SignedBeaconBlock<E>>(block_root)
+        self.hot_db.delete::<SignedBeaconBlock<E>>(block_root)
+    }
+
+    fn put_state_summary(
+        &self,
+        state_root: &Hash256,
+        summary: HotStateSummary,
+    ) -> Result<(), Error> {
+        self.hot_db.put(state_root, &summary).map_err(Into::into)
     }
 
     /// Store a state in the store.
@@ -155,17 +147,6 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
         &self,
         state_root: &Hash256,
         slot: Option<Slot>,
-    ) -> Result<Option<BeaconState<E>>, Error> {
-        self.get_state_with(state_root, slot)
-    }
-
-    /// Get a state from the store.
-    ///
-    /// Fetch a state from the store, controlling which cache fields are cloned.
-    fn get_state_with(
-        &self,
-        state_root: &Hash256,
-        slot: Option<Slot>,
     ) -> Result<Option<BeaconState<E>>, Error> {
         metrics::inc_counter(&metrics::BEACON_STATE_GET_COUNT);
 
@@ -203,96 +184,6 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
         Ok(())
     }
 
-    fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error> {
-        let mut guard = self.block_cache.lock();
-        self.hot_db.do_atomically(batch)?;
-        for op in batch {
-            match op {
-                StoreOp::DeleteBlock(block_hash) => {
-                    let untyped_hash: Hash256 = (*block_hash).into();
-                    guard.pop(&untyped_hash);
-                }
-                StoreOp::DeleteState(_, _) => (),
-            }
-        }
-        Ok(())
-    }
-
-    /// Advance the split point of the store, moving new finalized states to the freezer.
-    fn process_finalization(
-        store: Arc<Self>,
-        frozen_head_root: Hash256,
-        frozen_head: &BeaconState<E>,
-    ) -> Result<(), Error> {
-        debug!(
-            store.log,
-            "Freezer migration started";
-            "slot" => frozen_head.slot
-        );
-
-        // 0. Check that the migration is sensible.
-        // The new frozen head must increase the current split slot, and lie on an epoch
-        // boundary (in order for the hot state summary scheme to work).
-        let current_split_slot = store.get_split_slot();
-
-        if frozen_head.slot < current_split_slot {
-            return Err(HotColdDBError::FreezeSlotError {
-                current_split_slot,
-                proposed_split_slot: frozen_head.slot,
-            }
-            .into());
-        }
-
-        if frozen_head.slot % E::slots_per_epoch() != 0 {
-            return Err(HotColdDBError::FreezeSlotUnaligned(frozen_head.slot).into());
-        }
-
-        // 1. Copy all of the states between the head and the split slot, from the hot DB
-        // to the cold DB.
-        let state_root_iter = StateRootsIterator::new(store.clone(), frozen_head);
-
-        let mut to_delete = vec![];
-        for (state_root, slot) in
-            state_root_iter.take_while(|&(_, slot)| slot >= current_split_slot)
-        {
-            if slot % store.config.slots_per_restore_point == 0 {
-                let state: BeaconState<E> = store
-                    .hot_db
-                    .get_state(&state_root, None)?
-                    .ok_or_else(|| HotColdDBError::MissingStateToFreeze(state_root))?;
-
-                store.store_cold_state(&state_root, &state)?;
-            }
-
-            // Store a pointer from this state root to its slot, so we can later reconstruct states
-            // from their state root alone.
-            store.store_cold_state_slot(&state_root, slot)?;
-
-            // Delete the old summary, and the full state if we lie on an epoch boundary.
-            to_delete.push((state_root, slot));
-        }
-
-        // 2. Update the split slot
-        *store.split.write() = Split {
-            slot: frozen_head.slot,
-            state_root: frozen_head_root,
-        };
-        store.store_split()?;
-
-        // 3. Delete from the hot DB
-        for (state_root, slot) in to_delete {
-            store.delete_state(&state_root, slot)?;
-        }
-
-        debug!(
-            store.log,
-            "Freezer migration complete";
-            "slot" => frozen_head.slot
-        );
-
-        Ok(())
-    }
-
     fn forwards_block_roots_iterator(
         store: Arc<Self>,
         start_slot: Slot,
@@ -334,6 +225,33 @@ impl<E: EthSpec> Store<E> for HotColdDB<E> {
             }
         }
     }
+
+    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> {
+        self.hot_db.get(key)
+    }
+
+    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> {
+        let mut guard = self.block_cache.lock();
+        self.hot_db.do_atomically(batch)?;
+        for op in batch {
+            match op {
+                StoreOp::DeleteBlock(block_hash) => {
+                    let untyped_hash: Hash256 = (*block_hash).into();
+                    guard.pop(&untyped_hash);
+                }
+                StoreOp::DeleteState(_, _) => (),
+            }
+        }
+        Ok(())
+    }
 }
 
 impl<E: EthSpec> HotColdDB<E> {
@@ -408,9 +326,7 @@ impl<E: EthSpec> HotColdDB<E> {
             epoch_boundary_state_root,
         }) = self.load_hot_state_summary(state_root)?
         {
-            let boundary_state = self
+            let boundary_state = get_full_state(&self.hot_db, &epoch_boundary_state_root)?
-                .hot_db
-                .get_state(&epoch_boundary_state_root, None)?
                 .ok_or_else(|| {
                     HotColdDBError::MissingEpochBoundaryState(epoch_boundary_state_root)
                 })?;
@@ -758,6 +674,77 @@ 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>(
+    store: Arc<HotColdDB<E>>,
+    frozen_head_root: Hash256,
+    frozen_head: &BeaconState<E>,
+) -> Result<(), Error> {
+    debug!(
+        store.log,
+        "Freezer migration started";
+        "slot" => frozen_head.slot
+    );
+
+    // 0. Check that the migration is sensible.
+    // The new frozen head must increase the current split slot, and lie on an epoch
+    // boundary (in order for the hot state summary scheme to work).
+    let current_split_slot = store.get_split_slot();
+
+    if frozen_head.slot < current_split_slot {
+        return Err(HotColdDBError::FreezeSlotError {
+            current_split_slot,
+            proposed_split_slot: frozen_head.slot,
+        }
+        .into());
+    }
+
+    if frozen_head.slot % E::slots_per_epoch() != 0 {
+        return Err(HotColdDBError::FreezeSlotUnaligned(frozen_head.slot).into());
+    }
+
+    // 1. Copy all of the states between the head and the split slot, from the hot DB
+    // to the cold DB.
+    let state_root_iter = StateRootsIterator::new(store.clone(), frozen_head);
+
+    let mut to_delete = vec![];
+    for (state_root, slot) in state_root_iter.take_while(|&(_, slot)| slot >= current_split_slot) {
+        if slot % store.config.slots_per_restore_point == 0 {
+            let state: BeaconState<E> = get_full_state(&store.hot_db, &state_root)?
+                .ok_or_else(|| HotColdDBError::MissingStateToFreeze(state_root))?;
+
+            store.store_cold_state(&state_root, &state)?;
+        }
+
+        // Store a pointer from this state root to its slot, so we can later reconstruct states
+        // from their state root alone.
+        store.store_cold_state_slot(&state_root, slot)?;
+
+        // Delete the old summary, and the full state if we lie on an epoch boundary.
+        to_delete.push((state_root, slot));
+    }
+
+    // 2. Update the split slot
+    *store.split.write() = Split {
+        slot: frozen_head.slot,
+        state_root: frozen_head_root,
+    };
+    store.store_split()?;
+
+    // 3. Delete from the hot DB
+    for (state_root, slot) in to_delete {
+        store.delete_state(&state_root, slot)?;
+    }
+
+    debug!(
+        store.log,
+        "Freezer migration complete";
+        "slot" => frozen_head.slot
+    );
+
+    Ok(())
+}
+
 /// Struct for storing the split slot and state root in the database.
 #[derive(Debug, Clone, Copy, Default, Encode, Decode)]
 struct Split {
@@ -765,7 +752,7 @@ struct Split {
     state_root: Hash256,
 }
 
-impl SimpleStoreItem for Split {
+impl StoreItem for Split {
     fn db_column() -> DBColumn {
         DBColumn::BeaconMeta
     }
@@ -789,7 +776,7 @@ pub struct HotStateSummary {
     epoch_boundary_state_root: Hash256,
 }
 
-impl SimpleStoreItem for HotStateSummary {
+impl StoreItem for HotStateSummary {
     fn db_column() -> DBColumn {
         DBColumn::BeaconStateSummary
     }
@@ -832,7 +819,7 @@ struct ColdStateSummary {
     slot: Slot,
 }
 
-impl SimpleStoreItem for ColdStateSummary {
+impl StoreItem for ColdStateSummary {
     fn db_column() -> DBColumn {
         DBColumn::BeaconStateSummary
     }
@@ -852,7 +839,7 @@ struct RestorePointHash {
     state_root: Hash256,
 }
 
-impl SimpleStoreItem for RestorePointHash {
+impl StoreItem for RestorePointHash {
     fn db_column() -> DBColumn {
         DBColumn::BeaconRestorePoint
     }

beacon_node/store/src/impls.rs

@@ -4,7 +4,7 @@ use ssz::{Decode, Encode};
 pub mod beacon_state;
 pub mod partial_beacon_state;
 
-impl<T: EthSpec> SimpleStoreItem for SignedBeaconBlock<T> {
+impl<T: EthSpec> StoreItem for SignedBeaconBlock<T> {
     fn db_column() -> DBColumn {
         DBColumn::BeaconBlock
     }

beacon_node/store/src/impls/beacon_state.rs

@@ -4,8 +4,8 @@ use ssz_derive::{Decode, Encode};
 use std::convert::TryInto;
 use types::beacon_state::{CloneConfig, CommitteeCache, CACHED_EPOCHS};
 
-pub fn store_full_state<S: Store<E>, E: EthSpec>(
+pub fn store_full_state<KV: KeyValueStore<E>, E: EthSpec>(
-    store: &S,
+    store: &KV,
     state_root: &Hash256,
     state: &BeaconState<E>,
 ) -> Result<(), Error> {
@@ -24,13 +24,13 @@ pub fn store_full_state<S: Store<E>, E: EthSpec>(
     result
 }
 
-pub fn get_full_state<S: Store<E>, E: EthSpec>(
+pub fn get_full_state<KV: KeyValueStore<E>, E: EthSpec>(
-    store: &S,
+    db: &KV,
     state_root: &Hash256,
 ) -> Result<Option<BeaconState<E>>, Error> {
     let total_timer = metrics::start_timer(&metrics::BEACON_STATE_READ_TIMES);
 
-    match store.get_bytes(DBColumn::BeaconState.into(), state_root.as_bytes())? {
+    match db.get_bytes(DBColumn::BeaconState.into(), state_root.as_bytes())? {
         Some(bytes) => {
             let overhead_timer = metrics::start_timer(&metrics::BEACON_STATE_READ_OVERHEAD_TIMES);
             let container = StorageContainer::from_ssz_bytes(&bytes)?;

beacon_node/store/src/impls/partial_beacon_state.rs

@@ -1,7 +1,7 @@
 use crate::*;
 use ssz::{Decode, Encode};
 
-impl<T: EthSpec> SimpleStoreItem for PartialBeaconState<T> {
+impl<T: EthSpec> StoreItem for PartialBeaconState<T> {
     fn db_column() -> DBColumn {
         DBColumn::BeaconState
     }

beacon_node/store/src/iter.rs

@@ -42,11 +42,11 @@ impl<'a, U: Store<E>, E: EthSpec> AncestorIter<U, E, StateRootsIterator<'a, E, U
     }
 }
 
-pub struct StateRootsIterator<'a, T: EthSpec, U> {
+pub struct StateRootsIterator<'a, T: EthSpec, U: Store<T>> {
     inner: RootsIterator<'a, T, U>,
 }
 
-impl<'a, T: EthSpec, U> Clone for StateRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, U: Store<T>> Clone for StateRootsIterator<'a, T, U> {
     fn clone(&self) -> Self {
         Self {
             inner: self.inner.clone(),
@@ -86,11 +86,11 @@ 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> {
+pub struct BlockRootsIterator<'a, T: EthSpec, U: Store<T>> {
     inner: RootsIterator<'a, T, U>,
 }
 
-impl<'a, T: EthSpec, U> Clone for BlockRootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, U: Store<T>> Clone for BlockRootsIterator<'a, T, U> {
     fn clone(&self) -> Self {
         Self {
             inner: self.inner.clone(),
@@ -125,13 +125,13 @@ 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> {
+pub struct RootsIterator<'a, T: EthSpec, U: Store<T>> {
     store: Arc<U>,
     beacon_state: Cow<'a, BeaconState<T>>,
     slot: Slot,
 }
 
-impl<'a, T: EthSpec, U> Clone for RootsIterator<'a, T, U> {
+impl<'a, T: EthSpec, U: Store<T>> Clone for RootsIterator<'a, T, U> {
     fn clone(&self) -> Self {
         Self {
             store: self.store.clone(),
@@ -245,7 +245,7 @@ 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> {
+pub struct BlockIterator<'a, T: EthSpec, U: Store<T>> {
     roots: BlockRootsIterator<'a, T, U>,
 }
 

beacon_node/store/src/leveldb_store.rs

@@ -1,6 +1,4 @@
 use super::*;
-use crate::forwards_iter::SimpleForwardsBlockRootsIterator;
-use crate::impls::beacon_state::{get_full_state, store_full_state};
 use crate::metrics;
 use db_key::Key;
 use leveldb::database::batch::{Batch, Writebatch};
@@ -39,35 +37,12 @@ impl<E: EthSpec> LevelDB<E> {
     fn write_options(&self) -> WriteOptions {
         WriteOptions::new()
     }
-
-    fn get_key_for_col(col: &str, key: &[u8]) -> BytesKey {
-        let mut col = col.as_bytes().to_vec();
-        col.append(&mut key.to_vec());
-        BytesKey { key: col }
-    }
 }
 
-/// Used for keying leveldb.
+impl<E: EthSpec> KeyValueStore<E> for LevelDB<E> {
-pub struct BytesKey {
-    key: Vec<u8>,
-}
-
-impl Key for BytesKey {
-    fn from_u8(key: &[u8]) -> Self {
-        Self { key: key.to_vec() }
-    }
-
-    fn as_slice<T, F: Fn(&[u8]) -> T>(&self, f: F) -> T {
-        f(self.key.as_slice())
-    }
-}
-
-impl<E: EthSpec> Store<E> for LevelDB<E> {
-    type ForwardsBlockRootsIterator = SimpleForwardsBlockRootsIterator;
-
     /// Retrieve some bytes in `column` with `key`.
     fn get_bytes(&self, col: &str, key: &[u8]) -> Result<Option<Vec<u8>>, Error> {
-        let column_key = Self::get_key_for_col(col, key);
+        let column_key = get_key_for_col(col, key);
 
         metrics::inc_counter(&metrics::DISK_DB_READ_COUNT);
         let timer = metrics::start_timer(&metrics::DISK_DB_READ_TIMES);
@@ -86,7 +61,7 @@ impl<E: EthSpec> Store<E> for LevelDB<E> {
 
     /// Store some `value` in `column`, indexed with `key`.
     fn put_bytes(&self, col: &str, key: &[u8], val: &[u8]) -> Result<(), Error> {
-        let column_key = Self::get_key_for_col(col, key);
+        let column_key = get_key_for_col(col, key);
 
         metrics::inc_counter(&metrics::DISK_DB_WRITE_COUNT);
         metrics::inc_counter_by(&metrics::DISK_DB_WRITE_BYTES, val.len() as i64);
@@ -102,7 +77,7 @@ impl<E: EthSpec> Store<E> for LevelDB<E> {
 
     /// Return `true` if `key` exists in `column`.
     fn key_exists(&self, col: &str, key: &[u8]) -> Result<bool, Error> {
-        let column_key = Self::get_key_for_col(col, key);
+        let column_key = get_key_for_col(col, key);
 
         metrics::inc_counter(&metrics::DISK_DB_EXISTS_COUNT);
 
@@ -114,7 +89,7 @@ impl<E: EthSpec> Store<E> for LevelDB<E> {
 
     /// Removes `key` from `column`.
     fn key_delete(&self, col: &str, key: &[u8]) -> Result<(), Error> {
-        let column_key = Self::get_key_for_col(col, key);
+        let column_key = get_key_for_col(col, key);
 
         metrics::inc_counter(&metrics::DISK_DB_DELETE_COUNT);
 
@@ -123,56 +98,28 @@ impl<E: EthSpec> Store<E> for LevelDB<E> {
             .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 forwards_block_roots_iterator(
-        store: Arc<Self>,
-        start_slot: Slot,
-        end_state: BeaconState<E>,
-        end_block_root: Hash256,
-        _: &ChainSpec,
-    ) -> Self::ForwardsBlockRootsIterator {
-        SimpleForwardsBlockRootsIterator::new(store, start_slot, end_state, end_block_root)
-    }
-
     fn do_atomically(&self, ops_batch: &[StoreOp]) -> Result<(), Error> {
         let mut leveldb_batch = Writebatch::new();
         for op in ops_batch {
             match op {
                 StoreOp::DeleteBlock(block_hash) => {
                     let untyped_hash: Hash256 = (*block_hash).into();
-                    let key = Self::get_key_for_col(
+                    let key =
-                        DBColumn::BeaconBlock.into(),
+                        get_key_for_col(DBColumn::BeaconBlock.into(), untyped_hash.as_bytes());
-                        untyped_hash.as_bytes(),
-                    );
                     leveldb_batch.delete(key);
                 }
 
                 StoreOp::DeleteState(state_hash, slot) => {
                     let untyped_hash: Hash256 = (*state_hash).into();
-                    let state_summary_key = Self::get_key_for_col(
+                    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 = Self::get_key_for_col(
+                        let state_key =
-                            DBColumn::BeaconState.into(),
+                            get_key_for_col(DBColumn::BeaconState.into(), untyped_hash.as_bytes());
-                            untyped_hash.as_bytes(),
-                        );
                         leveldb_batch.delete(state_key);
                     }
                 }
@@ -183,6 +130,29 @@ impl<E: EthSpec> Store<E> for LevelDB<E> {
     }
 }
 
+impl<E: EthSpec> ItemStore<E> for LevelDB<E> {}
+
+/// Used for keying leveldb.
+pub struct BytesKey {
+    key: Vec<u8>,
+}
+
+impl Key for BytesKey {
+    fn from_u8(key: &[u8]) -> Self {
+        Self { key: key.to_vec() }
+    }
+
+    fn as_slice<T, F: Fn(&[u8]) -> T>(&self, f: F) -> T {
+        f(self.key.as_slice())
+    }
+}
+
+fn get_key_for_col(col: &str, key: &[u8]) -> BytesKey {
+    let mut col = col.as_bytes().to_vec();
+    col.append(&mut key.to_vec());
+    BytesKey { key: col }
+}
+
 impl From<LevelDBError> for Error {
     fn from(e: LevelDBError) -> Error {
         Error::DBError {

beacon_node/store/src/lib.rs

@@ -2,7 +2,7 @@
 //!
 //! Provides the following stores:
 //!
-//! - `DiskStore`: an on-disk store backed by leveldb. Used in production.
+//! - `HotColdDB`: an on-disk store backed by leveldb. Used in production.
 //! - `MemoryStore`: an in-memory store backed by a hash-map. Used for testing.
 //!
 //! Provides a simple API for storing/retrieving all types that sometimes needs type-hints. See
@@ -28,8 +28,8 @@ pub mod iter;
 use std::sync::Arc;
 
 pub use self::config::StoreConfig;
-pub use self::hot_cold_store::{HotColdDB as DiskStore, HotStateSummary};
+pub use self::hot_cold_store::{HotColdDB, HotStateSummary};
-pub use self::leveldb_store::LevelDB as SimpleDiskStore;
+pub use self::leveldb_store::LevelDB;
 pub use self::memory_store::MemoryStore;
 pub use self::partial_beacon_state::PartialBeaconState;
 pub use errors::Error;
@@ -38,14 +38,7 @@ pub use metrics::scrape_for_metrics;
 pub use state_batch::StateBatch;
 pub use types::*;
 
-/// An object capable of storing and retrieving objects implementing `StoreItem`.
+pub trait KeyValueStore<E: EthSpec>: Sync + Send + Sized + 'static {
-///
-/// 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 = (Hash256, Slot)>;
-
     /// Retrieve some bytes in `column` with `key`.
     fn get_bytes(&self, column: &str, key: &[u8]) -> Result<Option<Vec<u8>>, Error>;
 
@@ -58,8 +51,13 @@ pub trait Store<E: EthSpec>: Sync + Send + Sized + 'static {
     /// Removes `key` from `column`.
     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>;
+}
+
+pub trait ItemStore<E: EthSpec>: KeyValueStore<E> + Sync + Send + Sized + 'static {
     /// Store an item in `Self`.
-    fn put<I: SimpleStoreItem>(&self, key: &Hash256, item: &I) -> Result<(), Error> {
+    fn put<I: StoreItem>(&self, key: &Hash256, item: &I) -> Result<(), Error> {
         let column = I::db_column().into();
         let key = key.as_bytes();
 
@@ -68,7 +66,7 @@ pub trait Store<E: EthSpec>: Sync + Send + Sized + 'static {
     }
 
     /// Retrieve an item from `Self`.
-    fn get<I: SimpleStoreItem>(&self, key: &Hash256) -> Result<Option<I>, Error> {
+    fn get<I: StoreItem>(&self, key: &Hash256) -> Result<Option<I>, Error> {
         let column = I::db_column().into();
         let key = key.as_bytes();
 
@@ -79,7 +77,7 @@ pub trait Store<E: EthSpec>: Sync + Send + Sized + 'static {
     }
 
     /// Returns `true` if the given key represents an item in `Self`.
-    fn exists<I: SimpleStoreItem>(&self, key: &Hash256) -> Result<bool, Error> {
+    fn exists<I: StoreItem>(&self, key: &Hash256) -> Result<bool, Error> {
         let column = I::db_column().into();
         let key = key.as_bytes();
 
@@ -87,44 +85,40 @@ pub trait Store<E: EthSpec>: Sync + Send + Sized + 'static {
     }
 
     /// Remove an item from `Self`.
-    fn delete<I: SimpleStoreItem>(&self, key: &Hash256) -> Result<(), Error> {
+    fn delete<I: StoreItem>(&self, key: &Hash256) -> Result<(), Error> {
         let column = I::db_column().into();
         let key = key.as_bytes();
 
         self.key_delete(column, key)
     }
+}
+
+/// 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 = (Hash256, Slot)>;
 
     /// Store a block in the store.
-    fn put_block(&self, block_root: &Hash256, block: SignedBeaconBlock<E>) -> Result<(), Error> {
+    fn put_block(&self, block_root: &Hash256, block: SignedBeaconBlock<E>) -> Result<(), Error>;
-        self.put(block_root, &block)
-    }
 
     /// Fetch a block from the store.
-    fn get_block(&self, block_root: &Hash256) -> Result<Option<SignedBeaconBlock<E>>, Error> {
+    fn get_block(&self, block_root: &Hash256) -> Result<Option<SignedBeaconBlock<E>>, Error>;
-        self.get(block_root)
-    }
 
     /// Delete a block from the store.
-    fn delete_block(&self, block_root: &Hash256) -> Result<(), Error> {
+    fn delete_block(&self, block_root: &Hash256) -> Result<(), Error>;
-        self.key_delete(DBColumn::BeaconBlock.into(), block_root.as_bytes())
-    }
 
     /// Store a state in the store.
     fn put_state(&self, state_root: &Hash256, state: &BeaconState<E>) -> 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>;
-
     /// Store a state summary in the store.
-    // NOTE: this is a hack for the HotColdDb, we could consider splitting this
-    // trait and removing the generic `S: Store` types everywhere?
     fn put_state_summary(
         &self,
         state_root: &Hash256,
         summary: HotStateSummary,
-    ) -> Result<(), Error> {
+    ) -> Result<(), Error>;
-        self.put(state_root, &summary).map_err(Into::into)
-    }
 
     /// Fetch a state from the store.
     fn get_state(
@@ -133,33 +127,12 @@ pub trait Store<E: EthSpec>: Sync + Send + Sized + 'static {
         slot: Option<Slot>,
     ) -> Result<Option<BeaconState<E>>, Error>;
 
-    /// Fetch a state from the store, controlling which cache fields are cloned.
-    fn get_state_with(
-        &self,
-        state_root: &Hash256,
-        slot: Option<Slot>,
-    ) -> Result<Option<BeaconState<E>>, Error> {
-        // Default impl ignores config. Overriden in `HotColdDb`.
-        self.get_state(state_root, slot)
-    }
-
     /// Delete a state from the store.
-    fn delete_state(&self, state_root: &Hash256, _slot: Slot) -> Result<(), Error> {
+    fn delete_state(&self, state_root: &Hash256, _slot: Slot) -> Result<(), Error>;
-        self.key_delete(DBColumn::BeaconState.into(), state_root.as_bytes())
-    }
-
-    /// (Optionally) Move all data before the frozen slot to the freezer database.
-    fn process_finalization(
-        _store: Arc<Self>,
-        _frozen_head_root: Hash256,
-        _frozen_head: &BeaconState<E>,
-    ) -> Result<(), Error> {
-        Ok(())
-    }
 
     /// 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 `DiskStore`.
+    /// 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
@@ -175,28 +148,18 @@ pub trait Store<E: EthSpec>: Sync + Send + Sized + 'static {
         spec: &ChainSpec,
     ) -> Self::ForwardsBlockRootsIterator;
 
-    /// 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> {
+    ) -> Result<Option<BeaconState<E>>, Error>;
-        // The default implementation is not very efficient, but isn't used in prod.
+
-        // See `HotColdDB` for the optimized implementation.
+    fn put_item<I: StoreItem>(&self, key: &Hash256, item: &I) -> Result<(), Error>;
-        if let Some(state) = self.get_state(state_root, None)? {
+
-            let epoch_boundary_slot = state.slot / E::slots_per_epoch() * E::slots_per_epoch();
+    fn get_item<I: StoreItem>(&self, key: &Hash256) -> Result<Option<I>, Error>;
-            if state.slot == epoch_boundary_slot {
+
-                Ok(Some(state))
+    fn item_exists<I: StoreItem>(&self, key: &Hash256) -> Result<bool, Error>;
-            } else {
+
-                let epoch_boundary_state_root = state.get_state_root(epoch_boundary_slot)?;
+    fn do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error>;
-                self.get_state(epoch_boundary_state_root, Some(epoch_boundary_slot))
-            }
-        } else {
-            Ok(None)
-        }
-    }
 }
 
 /// Reified key-value storage operation.  Helps in modifying the storage atomically.
@@ -252,7 +215,7 @@ impl Into<&'static str> for DBColumn {
 }
 
 /// An item that may stored in a `Store` by serializing and deserializing from bytes.
-pub trait SimpleStoreItem: Sized {
+pub trait StoreItem: Sized {
     /// Identifies which column this item should be placed in.
     fn db_column() -> DBColumn;
 
@@ -278,7 +241,7 @@ mod tests {
         b: u64,
     }
 
-    impl SimpleStoreItem for StorableThing {
+    impl StoreItem for StorableThing {
         fn db_column() -> DBColumn {
             DBColumn::BeaconBlock
         }
@@ -292,7 +255,7 @@ mod tests {
         }
     }
 
-    fn test_impl(store: impl Store<MinimalEthSpec>) {
+    fn test_impl(store: impl ItemStore<MinimalEthSpec>) {
         let key = Hash256::random();
         let item = StorableThing { a: 1, b: 42 };
 
@@ -312,31 +275,11 @@ mod tests {
         assert_eq!(store.get::<StorableThing>(&key).unwrap(), None);
     }
 
-    #[test]
-    fn diskdb() {
-        use sloggers::{null::NullLoggerBuilder, Build};
-
-        let hot_dir = tempdir().unwrap();
-        let cold_dir = tempdir().unwrap();
-        let spec = MinimalEthSpec::default_spec();
-        let log = NullLoggerBuilder.build().unwrap();
-        let store = DiskStore::open(
-            &hot_dir.path(),
-            &cold_dir.path(),
-            StoreConfig::default(),
-            spec,
-            log,
-        )
-        .unwrap();
-
-        test_impl(store);
-    }
-
     #[test]
     fn simplediskdb() {
         let dir = tempdir().unwrap();
         let path = dir.path();
-        let store = SimpleDiskStore::open(&path).unwrap();
+        let store = LevelDB::open(&path).unwrap();
 
         test_impl(store);
     }

beacon_node/store/src/memory_store.rs

@@ -1,6 +1,8 @@
-use super::{DBColumn, Error, Store, StoreOp};
+use super::{DBColumn, Error, ItemStore, KeyValueStore, Store, StoreOp};
 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;
@@ -40,9 +42,7 @@ impl<E: EthSpec> MemoryStore<E> {
     }
 }
 
-impl<E: EthSpec> Store<E> for MemoryStore<E> {
+impl<E: EthSpec> KeyValueStore<E> for MemoryStore<E> {
-    type ForwardsBlockRootsIterator = SimpleForwardsBlockRootsIterator;
-
     /// 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);
@@ -75,20 +75,6 @@ impl<E: EthSpec> Store<E> for MemoryStore<E> {
         Ok(())
     }
 
-    /// 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 do_atomically(&self, batch: &[StoreOp]) -> Result<(), Error> {
         for op in batch {
             match op {
@@ -112,6 +98,50 @@ impl<E: EthSpec> Store<E> for MemoryStore<E> {
         }
         Ok(())
     }
+}
+
+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>,
@@ -122,4 +152,43 @@ impl<E: EthSpec> Store<E> for MemoryStore<E> {
     ) -> Self::ForwardsBlockRootsIterator {
         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/partial_beacon_state.rs

@@ -2,7 +2,7 @@ use crate::chunked_vector::{
     load_variable_list_from_db, load_vector_from_db, BlockRoots, HistoricalRoots, RandaoMixes,
     StateRoots,
 };
-use crate::{Error, Store};
+use crate::{Error, KeyValueStore};
 use ssz_derive::{Decode, Encode};
 use std::convert::TryInto;
 use types::*;
@@ -113,7 +113,7 @@ impl<T: EthSpec> PartialBeaconState<T> {
         }
     }
 
-    pub fn load_block_roots<S: Store<T>>(
+    pub fn load_block_roots<S: KeyValueStore<T>>(
         &mut self,
         store: &S,
         spec: &ChainSpec,
@@ -126,7 +126,7 @@ impl<T: EthSpec> PartialBeaconState<T> {
         Ok(())
     }
 
-    pub fn load_state_roots<S: Store<T>>(
+    pub fn load_state_roots<S: KeyValueStore<T>>(
         &mut self,
         store: &S,
         spec: &ChainSpec,
@@ -139,7 +139,7 @@ impl<T: EthSpec> PartialBeaconState<T> {
         Ok(())
     }
 
-    pub fn load_historical_roots<S: Store<T>>(
+    pub fn load_historical_roots<S: KeyValueStore<T>>(
         &mut self,
         store: &S,
         spec: &ChainSpec,
@@ -152,7 +152,7 @@ impl<T: EthSpec> PartialBeaconState<T> {
         Ok(())
     }
 
-    pub fn load_randao_mixes<S: Store<T>>(
+    pub fn load_randao_mixes<S: KeyValueStore<T>>(
         &mut self,
         store: &S,
         spec: &ChainSpec,

consensus/ssz/src/encode.rs

@@ -91,13 +91,6 @@ pub struct SszEncoder<'a> {
 }
 
 impl<'a> SszEncoder<'a> {
-    /// Instantiate a new encoder for encoding a SSZ list.
-    ///
-    /// Identical to `Self::container`.
-    pub fn list(buf: &'a mut Vec<u8>, num_fixed_bytes: usize) -> Self {
-        Self::container(buf, num_fixed_bytes)
-    }
-
     /// Instantiate a new encoder for encoding a SSZ container.
     pub fn container(buf: &'a mut Vec<u8>, num_fixed_bytes: usize) -> Self {
         buf.reserve(num_fixed_bytes);

consensus/ssz/src/encode/impls.rs

@@ -256,7 +256,8 @@ macro_rules! impl_for_vec {
                         item.ssz_append(buf);
                     }
                 } else {
-                    let mut encoder = SszEncoder::list(buf, self.len() * BYTES_PER_LENGTH_OFFSET);
+                    let mut encoder =
+                        SszEncoder::container(buf, self.len() * BYTES_PER_LENGTH_OFFSET);
 
                     for item in self {
                         encoder.append(item);

consensus/ssz_types/src/fixed_vector.rs

@@ -196,7 +196,8 @@ where
                 item.ssz_append(buf);
             }
         } else {
-            let mut encoder = ssz::SszEncoder::list(buf, self.len() * ssz::BYTES_PER_LENGTH_OFFSET);
+            let mut encoder =
+                ssz::SszEncoder::container(buf, self.len() * ssz::BYTES_PER_LENGTH_OFFSET);
 
             for item in &self.vec {
                 encoder.append(item);