DB migration for fork choice cleanup (#4265)

## Issue Addressed

#4233

## Proposed Changes

Remove the `best_justified_checkpoint` from the `PersistedForkChoiceStore` type as it is now unused.
Additionally, remove the `Option`'s wrapping the `justified_checkpoint` and `finalized_checkpoint` fields on `ProtoNode` which were only present to facilitate a previous migration.

Include the necessary code to facilitate the migration to a new DB schema.

Cargo.lock

@@ -6196,6 +6196,7 @@ dependencies = [
  "serde",
  "serde_derive",
  "serde_yaml",
+ "superstruct 0.5.0",
  "types",
 ]
 

beacon_node/beacon_chain/src/beacon_fork_choice_store.rs

@@ -218,7 +218,6 @@ where
             finalized_checkpoint: self.finalized_checkpoint,
             justified_checkpoint: self.justified_checkpoint,
             justified_balances: self.justified_balances.effective_balances.clone(),
-            best_justified_checkpoint: JUNK_BEST_JUSTIFIED_CHECKPOINT,
             unrealized_justified_checkpoint: self.unrealized_justified_checkpoint,
             unrealized_finalized_checkpoint: self.unrealized_finalized_checkpoint,
             proposer_boost_root: self.proposer_boost_root,
@@ -355,24 +354,62 @@ where
     }
 }
 
+pub type PersistedForkChoiceStore = PersistedForkChoiceStoreV17;
+
 /// A container which allows persisting the `BeaconForkChoiceStore` to the on-disk database.
-#[superstruct(variants(V11), variant_attributes(derive(Encode, Decode)), no_enum)]
+#[superstruct(
+    variants(V11, V17),
+    variant_attributes(derive(Encode, Decode)),
+    no_enum
+)]
 pub struct PersistedForkChoiceStore {
-    #[superstruct(only(V11))]
+    #[superstruct(only(V11, V17))]
     pub balances_cache: BalancesCacheV8,
     pub time: Slot,
     pub finalized_checkpoint: Checkpoint,
     pub justified_checkpoint: Checkpoint,
     pub justified_balances: Vec<u64>,
+    #[superstruct(only(V11))]
     pub best_justified_checkpoint: Checkpoint,
-    #[superstruct(only(V11))]
+    #[superstruct(only(V11, V17))]
     pub unrealized_justified_checkpoint: Checkpoint,
-    #[superstruct(only(V11))]
+    #[superstruct(only(V11, V17))]
     pub unrealized_finalized_checkpoint: Checkpoint,
-    #[superstruct(only(V11))]
+    #[superstruct(only(V11, V17))]
     pub proposer_boost_root: Hash256,
-    #[superstruct(only(V11))]
+    #[superstruct(only(V11, V17))]
     pub equivocating_indices: BTreeSet<u64>,
 }
 
-pub type PersistedForkChoiceStore = PersistedForkChoiceStoreV11;
+impl Into<PersistedForkChoiceStore> for PersistedForkChoiceStoreV11 {
+    fn into(self) -> PersistedForkChoiceStore {
+        PersistedForkChoiceStore {
+            balances_cache: self.balances_cache,
+            time: self.time,
+            finalized_checkpoint: self.finalized_checkpoint,
+            justified_checkpoint: self.justified_checkpoint,
+            justified_balances: self.justified_balances,
+            unrealized_justified_checkpoint: self.unrealized_justified_checkpoint,
+            unrealized_finalized_checkpoint: self.unrealized_finalized_checkpoint,
+            proposer_boost_root: self.proposer_boost_root,
+            equivocating_indices: self.equivocating_indices,
+        }
+    }
+}
+
+impl Into<PersistedForkChoiceStoreV11> for PersistedForkChoiceStore {
+    fn into(self) -> PersistedForkChoiceStoreV11 {
+        PersistedForkChoiceStoreV11 {
+            balances_cache: self.balances_cache,
+            time: self.time,
+            finalized_checkpoint: self.finalized_checkpoint,
+            justified_checkpoint: self.justified_checkpoint,
+            justified_balances: self.justified_balances,
+            best_justified_checkpoint: JUNK_BEST_JUSTIFIED_CHECKPOINT,
+            unrealized_justified_checkpoint: self.unrealized_justified_checkpoint,
+            unrealized_finalized_checkpoint: self.unrealized_finalized_checkpoint,
+            proposer_boost_root: self.proposer_boost_root,
+            equivocating_indices: self.equivocating_indices,
+        }
+    }
+}

beacon_node/beacon_chain/src/persisted_fork_choice.rs

@@ -1,17 +1,41 @@
-use crate::beacon_fork_choice_store::PersistedForkChoiceStoreV11;
+use crate::beacon_fork_choice_store::{PersistedForkChoiceStoreV11, PersistedForkChoiceStoreV17};
 use ssz::{Decode, Encode};
 use ssz_derive::{Decode, Encode};
 use store::{DBColumn, Error, StoreItem};
 use superstruct::superstruct;
 
 // If adding a new version you should update this type alias and fix the breakages.
-pub type PersistedForkChoice = PersistedForkChoiceV11;
+pub type PersistedForkChoice = PersistedForkChoiceV17;
 
-#[superstruct(variants(V11), variant_attributes(derive(Encode, Decode)), no_enum)]
+#[superstruct(
+    variants(V11, V17),
+    variant_attributes(derive(Encode, Decode)),
+    no_enum
+)]
 pub struct PersistedForkChoice {
     pub fork_choice: fork_choice::PersistedForkChoice,
     #[superstruct(only(V11))]
     pub fork_choice_store: PersistedForkChoiceStoreV11,
+    #[superstruct(only(V17))]
+    pub fork_choice_store: PersistedForkChoiceStoreV17,
+}
+
+impl Into<PersistedForkChoice> for PersistedForkChoiceV11 {
+    fn into(self) -> PersistedForkChoice {
+        PersistedForkChoice {
+            fork_choice: self.fork_choice,
+            fork_choice_store: self.fork_choice_store.into(),
+        }
+    }
+}
+
+impl Into<PersistedForkChoiceV11> for PersistedForkChoice {
+    fn into(self) -> PersistedForkChoiceV11 {
+        PersistedForkChoiceV11 {
+            fork_choice: self.fork_choice,
+            fork_choice_store: self.fork_choice_store.into(),
+        }
+    }
 }
 
 macro_rules! impl_store_item {
@@ -33,3 +57,4 @@ macro_rules! impl_store_item {
 }
 
 impl_store_item!(PersistedForkChoiceV11);
+impl_store_item!(PersistedForkChoiceV17);

beacon_node/beacon_chain/src/schema_change.rs

@@ -4,6 +4,7 @@ mod migration_schema_v13;
 mod migration_schema_v14;
 mod migration_schema_v15;
 mod migration_schema_v16;
+mod migration_schema_v17;
 
 use crate::beacon_chain::{BeaconChainTypes, ETH1_CACHE_DB_KEY};
 use crate::eth1_chain::SszEth1;
@@ -141,6 +142,14 @@ pub fn migrate_schema<T: BeaconChainTypes>(
             let ops = migration_schema_v16::downgrade_from_v16::<T>(db.clone(), log)?;
             db.store_schema_version_atomically(to, ops)
         }
+        (SchemaVersion(16), SchemaVersion(17)) => {
+            let ops = migration_schema_v17::upgrade_to_v17::<T>(db.clone(), log)?;
+            db.store_schema_version_atomically(to, ops)
+        }
+        (SchemaVersion(17), SchemaVersion(16)) => {
+            let ops = migration_schema_v17::downgrade_from_v17::<T>(db.clone(), log)?;
+            db.store_schema_version_atomically(to, ops)
+        }
         // Anything else is an error.
         (_, _) => Err(HotColdDBError::UnsupportedSchemaVersion {
             target_version: to,

beacon_node/beacon_chain/src/schema_change/migration_schema_v17.rs

@@ -0,0 +1,88 @@
+use crate::beacon_chain::{BeaconChainTypes, FORK_CHOICE_DB_KEY};
+use crate::persisted_fork_choice::{PersistedForkChoiceV11, PersistedForkChoiceV17};
+use proto_array::core::{SszContainerV16, SszContainerV17};
+use slog::{debug, Logger};
+use ssz::{Decode, Encode};
+use std::sync::Arc;
+use store::{Error, HotColdDB, KeyValueStoreOp, StoreItem};
+
+pub fn upgrade_fork_choice(
+    mut fork_choice: PersistedForkChoiceV11,
+) -> Result<PersistedForkChoiceV17, Error> {
+    let ssz_container_v16 = SszContainerV16::from_ssz_bytes(
+        &fork_choice.fork_choice.proto_array_bytes,
+    )
+    .map_err(|e| {
+        Error::SchemaMigrationError(format!(
+            "Failed to decode ProtoArrayForkChoice during schema migration: {:?}",
+            e
+        ))
+    })?;
+
+    let ssz_container_v17: SszContainerV17 = ssz_container_v16.try_into().map_err(|e| {
+        Error::SchemaMigrationError(format!(
+            "Missing checkpoint during schema migration: {:?}",
+            e
+        ))
+    })?;
+    fork_choice.fork_choice.proto_array_bytes = ssz_container_v17.as_ssz_bytes();
+
+    Ok(fork_choice.into())
+}
+
+pub fn downgrade_fork_choice(
+    mut fork_choice: PersistedForkChoiceV17,
+) -> Result<PersistedForkChoiceV11, Error> {
+    let ssz_container_v17 = SszContainerV17::from_ssz_bytes(
+        &fork_choice.fork_choice.proto_array_bytes,
+    )
+    .map_err(|e| {
+        Error::SchemaMigrationError(format!(
+            "Failed to decode ProtoArrayForkChoice during schema migration: {:?}",
+            e
+        ))
+    })?;
+
+    let ssz_container_v16: SszContainerV16 = ssz_container_v17.into();
+    fork_choice.fork_choice.proto_array_bytes = ssz_container_v16.as_ssz_bytes();
+
+    Ok(fork_choice.into())
+}
+
+pub fn upgrade_to_v17<T: BeaconChainTypes>(
+    db: Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>,
+    log: Logger,
+) -> Result<Vec<KeyValueStoreOp>, Error> {
+    // Get persisted_fork_choice.
+    let v11 = db
+        .get_item::<PersistedForkChoiceV11>(&FORK_CHOICE_DB_KEY)?
+        .ok_or_else(|| Error::SchemaMigrationError("fork choice missing from database".into()))?;
+
+    let v17 = upgrade_fork_choice(v11)?;
+
+    debug!(
+        log,
+        "Removing unused best_justified_checkpoint from fork choice store."
+    );
+
+    Ok(vec![v17.as_kv_store_op(FORK_CHOICE_DB_KEY)])
+}
+
+pub fn downgrade_from_v17<T: BeaconChainTypes>(
+    db: Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>,
+    log: Logger,
+) -> Result<Vec<KeyValueStoreOp>, Error> {
+    // Get persisted_fork_choice.
+    let v17 = db
+        .get_item::<PersistedForkChoiceV17>(&FORK_CHOICE_DB_KEY)?
+        .ok_or_else(|| Error::SchemaMigrationError("fork choice missing from database".into()))?;
+
+    let v11 = downgrade_fork_choice(v17)?;
+
+    debug!(
+        log,
+        "Adding junk best_justified_checkpoint to fork choice store."
+    );
+
+    Ok(vec![v11.as_kv_store_op(FORK_CHOICE_DB_KEY)])
+}

beacon_node/http_api/src/lib.rs

@@ -2202,12 +2202,8 @@ pub fn serve<T: BeaconChainTypes>(
                                 .parent
                                 .and_then(|index| proto_array.nodes.get(index))
                                 .map(|parent| parent.root),
-                            justified_epoch: node
+                            justified_epoch: node.justified_checkpoint.epoch,
-                                .justified_checkpoint
+                            finalized_epoch: node.finalized_checkpoint.epoch,
-                                .map(|checkpoint| checkpoint.epoch),
-                            finalized_epoch: node
-                                .finalized_checkpoint
-                                .map(|checkpoint| checkpoint.epoch),
                             weight: node.weight,
                             validity: execution_status,
                             execution_block_hash: node

beacon_node/http_api/tests/tests.rs

@@ -1956,8 +1956,8 @@ impl ApiTester {
                         .parent
                         .and_then(|index| expected_proto_array.nodes.get(index))
                         .map(|parent| parent.root),
-                    justified_epoch: node.justified_checkpoint.map(|checkpoint| checkpoint.epoch),
+                    justified_epoch: node.justified_checkpoint.epoch,
-                    finalized_epoch: node.finalized_checkpoint.map(|checkpoint| checkpoint.epoch),
+                    finalized_epoch: node.finalized_checkpoint.epoch,
                     weight: node.weight,
                     validity: execution_status,
                     execution_block_hash: node

beacon_node/store/src/metadata.rs

@@ -4,7 +4,7 @@ use ssz::{Decode, Encode};
 use ssz_derive::{Decode, Encode};
 use types::{Checkpoint, Hash256, Slot};
 
-pub const CURRENT_SCHEMA_VERSION: SchemaVersion = SchemaVersion(16);
+pub const CURRENT_SCHEMA_VERSION: SchemaVersion = SchemaVersion(17);
 
 // All the keys that get stored under the `BeaconMeta` column.
 //

common/eth2/src/types.rs

@@ -1229,8 +1229,8 @@ pub struct ForkChoiceNode {
     pub slot: Slot,
     pub block_root: Hash256,
     pub parent_root: Option<Hash256>,
-    pub justified_epoch: Option<Epoch>,
+    pub justified_epoch: Epoch,
-    pub finalized_epoch: Option<Epoch>,
+    pub finalized_epoch: Epoch,
     #[serde(with = "serde_utils::quoted_u64")]
     pub weight: u64,
     pub validity: Option<String>,

consensus/proto_array/Cargo.toml

@@ -16,3 +16,4 @@ serde = "1.0.116"
 serde_derive = "1.0.116"
 serde_yaml = "0.8.13"
 safe_arith = { path = "../safe_arith" }
+superstruct = "0.5.0"

consensus/proto_array/src/error.rs

@@ -14,6 +14,8 @@ pub enum Error {
     InvalidBestDescendant(usize),
     InvalidParentDelta(usize),
     InvalidNodeDelta(usize),
+    MissingJustifiedCheckpoint,
+    MissingFinalizedCheckpoint,
     DeltaOverflow(usize),
     ProposerBoostOverflow(usize),
     ReOrgThresholdOverflow,
@@ -67,6 +69,6 @@ pub struct InvalidBestNodeInfo {
     pub justified_checkpoint: Checkpoint,
     pub finalized_checkpoint: Checkpoint,
     pub head_root: Hash256,
-    pub head_justified_checkpoint: Option<Checkpoint>,
+    pub head_justified_checkpoint: Checkpoint,
-    pub head_finalized_checkpoint: Option<Checkpoint>,
+    pub head_finalized_checkpoint: Checkpoint,
 }

consensus/proto_array/src/lib.rs

@@ -16,5 +16,5 @@ pub use error::Error;
 pub mod core {
     pub use super::proto_array::{ProposerBoost, ProtoArray, ProtoNode};
     pub use super::proto_array_fork_choice::VoteTracker;
-    pub use super::ssz_container::SszContainer;
+    pub use super::ssz_container::{SszContainer, SszContainerV16, SszContainerV17};
 }

consensus/proto_array/src/proto_array.rs

@@ -5,6 +5,7 @@ use ssz::four_byte_option_impl;
 use ssz::Encode;
 use ssz_derive::{Decode, Encode};
 use std::collections::{HashMap, HashSet};
+use superstruct::superstruct;
 use types::{
     AttestationShufflingId, ChainSpec, Checkpoint, Epoch, EthSpec, ExecutionBlockHash, Hash256,
     Slot,
@@ -66,7 +67,13 @@ impl InvalidationOperation {
     }
 }
 
-#[derive(Clone, PartialEq, Debug, Encode, Decode, Serialize, Deserialize)]
+pub type ProtoNode = ProtoNodeV17;
+
+#[superstruct(
+    variants(V16, V17),
+    variant_attributes(derive(Clone, PartialEq, Debug, Encode, Decode, Serialize, Deserialize)),
+    no_enum
+)]
 pub struct ProtoNode {
     /// The `slot` is not necessary for `ProtoArray`, it just exists so external components can
     /// easily query the block slot. This is useful for upstream fork choice logic.
@@ -85,10 +92,16 @@ pub struct ProtoNode {
     pub root: Hash256,
     #[ssz(with = "four_byte_option_usize")]
     pub parent: Option<usize>,
+    #[superstruct(only(V16))]
     #[ssz(with = "four_byte_option_checkpoint")]
     pub justified_checkpoint: Option<Checkpoint>,
+    #[superstruct(only(V16))]
     #[ssz(with = "four_byte_option_checkpoint")]
     pub finalized_checkpoint: Option<Checkpoint>,
+    #[superstruct(only(V17))]
+    pub justified_checkpoint: Checkpoint,
+    #[superstruct(only(V17))]
+    pub finalized_checkpoint: Checkpoint,
     pub weight: u64,
     #[ssz(with = "four_byte_option_usize")]
     pub best_child: Option<usize>,
@@ -103,6 +116,57 @@ pub struct ProtoNode {
     pub unrealized_finalized_checkpoint: Option<Checkpoint>,
 }
 
+impl TryInto<ProtoNode> for ProtoNodeV16 {
+    type Error = Error;
+
+    fn try_into(self) -> Result<ProtoNode, Error> {
+        let result = ProtoNode {
+            slot: self.slot,
+            state_root: self.state_root,
+            target_root: self.target_root,
+            current_epoch_shuffling_id: self.current_epoch_shuffling_id,
+            next_epoch_shuffling_id: self.next_epoch_shuffling_id,
+            root: self.root,
+            parent: self.parent,
+            justified_checkpoint: self
+                .justified_checkpoint
+                .ok_or(Error::MissingJustifiedCheckpoint)?,
+            finalized_checkpoint: self
+                .finalized_checkpoint
+                .ok_or(Error::MissingFinalizedCheckpoint)?,
+            weight: self.weight,
+            best_child: self.best_child,
+            best_descendant: self.best_descendant,
+            execution_status: self.execution_status,
+            unrealized_justified_checkpoint: self.unrealized_justified_checkpoint,
+            unrealized_finalized_checkpoint: self.unrealized_finalized_checkpoint,
+        };
+        Ok(result)
+    }
+}
+
+impl Into<ProtoNodeV16> for ProtoNode {
+    fn into(self) -> ProtoNodeV16 {
+        ProtoNodeV16 {
+            slot: self.slot,
+            state_root: self.state_root,
+            target_root: self.target_root,
+            current_epoch_shuffling_id: self.current_epoch_shuffling_id,
+            next_epoch_shuffling_id: self.next_epoch_shuffling_id,
+            root: self.root,
+            parent: self.parent,
+            justified_checkpoint: Some(self.justified_checkpoint),
+            finalized_checkpoint: Some(self.finalized_checkpoint),
+            weight: self.weight,
+            best_child: self.best_child,
+            best_descendant: self.best_descendant,
+            execution_status: self.execution_status,
+            unrealized_justified_checkpoint: self.unrealized_justified_checkpoint,
+            unrealized_finalized_checkpoint: self.unrealized_finalized_checkpoint,
+        }
+    }
+}
+
 #[derive(PartialEq, Debug, Encode, Decode, Serialize, Deserialize, Copy, Clone)]
 pub struct ProposerBoost {
     pub root: Hash256,
@@ -320,8 +384,8 @@ impl ProtoArray {
             parent: block
                 .parent_root
                 .and_then(|parent| self.indices.get(&parent).copied()),
-            justified_checkpoint: Some(block.justified_checkpoint),
+            justified_checkpoint: block.justified_checkpoint,
-            finalized_checkpoint: Some(block.finalized_checkpoint),
+            finalized_checkpoint: block.finalized_checkpoint,
             weight: 0,
             best_child: None,
             best_descendant: None,
@@ -883,14 +947,7 @@ impl ProtoArray {
         let genesis_epoch = Epoch::new(0);
         let current_epoch = current_slot.epoch(E::slots_per_epoch());
         let node_epoch = node.slot.epoch(E::slots_per_epoch());
-        let node_justified_checkpoint =
+        let node_justified_checkpoint = node.justified_checkpoint;
-            if let Some(justified_checkpoint) = node.justified_checkpoint {
-                justified_checkpoint
-            } else {
-                // The node does not have any information about the justified
-                // checkpoint. This indicates an inconsistent proto-array.
-                return false;
-            };
 
         let voting_source = if current_epoch > node_epoch {
             // The block is from a prior epoch, the voting source will be pulled-up.
@@ -998,9 +1055,13 @@ impl ProtoArray {
         // Run this check once, outside of the loop rather than inside the loop.
         // If the conditions don't match for this node then they're unlikely to
         // start matching for its ancestors.
+        for checkpoint in &[node.finalized_checkpoint, node.justified_checkpoint] {
+            if checkpoint == &self.finalized_checkpoint {
+                return true;
+            }
+        }
+
         for checkpoint in &[
-            node.finalized_checkpoint,
-            node.justified_checkpoint,
             node.unrealized_finalized_checkpoint,
             node.unrealized_justified_checkpoint,
         ] {

consensus/proto_array/src/proto_array_fork_choice.rs

@@ -754,29 +754,20 @@ impl ProtoArrayForkChoice {
             .and_then(|i| self.proto_array.nodes.get(i))
             .map(|parent| parent.root);
 
-        // If a node does not have a `finalized_checkpoint` or `justified_checkpoint` populated,
+        Some(Block {
-        // it means it is not a descendant of the finalized checkpoint, so it is valid to return
+            slot: block.slot,
-        // `None` here.
+            root: block.root,
-        if let (Some(justified_checkpoint), Some(finalized_checkpoint)) =
+            parent_root,
-            (block.justified_checkpoint, block.finalized_checkpoint)
+            state_root: block.state_root,
-        {
+            target_root: block.target_root,
-            Some(Block {
+            current_epoch_shuffling_id: block.current_epoch_shuffling_id.clone(),
-                slot: block.slot,
+            next_epoch_shuffling_id: block.next_epoch_shuffling_id.clone(),
-                root: block.root,
+            justified_checkpoint: block.justified_checkpoint,
-                parent_root,
+            finalized_checkpoint: block.finalized_checkpoint,
-                state_root: block.state_root,
+            execution_status: block.execution_status,
-                target_root: block.target_root,
+            unrealized_justified_checkpoint: block.unrealized_justified_checkpoint,
-                current_epoch_shuffling_id: block.current_epoch_shuffling_id.clone(),
+            unrealized_finalized_checkpoint: block.unrealized_finalized_checkpoint,
-                next_epoch_shuffling_id: block.next_epoch_shuffling_id.clone(),
+        })
-                justified_checkpoint,
-                finalized_checkpoint,
-                execution_status: block.execution_status,
-                unrealized_justified_checkpoint: block.unrealized_justified_checkpoint,
-                unrealized_finalized_checkpoint: block.unrealized_finalized_checkpoint,
-            })
-        } else {
-            None
-        }
     }
 
     /// Returns the `block.execution_status` field, if the block is present.

consensus/proto_array/src/ssz_container.rs

@@ -1,6 +1,6 @@
 use crate::proto_array::ProposerBoost;
 use crate::{
-    proto_array::{ProtoArray, ProtoNode},
+    proto_array::{ProtoArray, ProtoNodeV16, ProtoNodeV17},
     proto_array_fork_choice::{ElasticList, ProtoArrayForkChoice, VoteTracker},
     Error, JustifiedBalances,
 };
@@ -8,24 +8,71 @@ use ssz::{four_byte_option_impl, Encode};
 use ssz_derive::{Decode, Encode};
 use std::collections::HashMap;
 use std::convert::TryFrom;
+use superstruct::superstruct;
 use types::{Checkpoint, Hash256};
 
 // Define a "legacy" implementation of `Option<usize>` which uses four bytes for encoding the union
 // selector.
 four_byte_option_impl!(four_byte_option_checkpoint, Checkpoint);
 
-#[derive(Encode, Decode)]
+pub type SszContainer = SszContainerV17;
+
+#[superstruct(
+    variants(V16, V17),
+    variant_attributes(derive(Encode, Decode)),
+    no_enum
+)]
 pub struct SszContainer {
     pub votes: Vec<VoteTracker>,
     pub balances: Vec<u64>,
     pub prune_threshold: usize,
     pub justified_checkpoint: Checkpoint,
     pub finalized_checkpoint: Checkpoint,
-    pub nodes: Vec<ProtoNode>,
+    #[superstruct(only(V16))]
+    pub nodes: Vec<ProtoNodeV16>,
+    #[superstruct(only(V17))]
+    pub nodes: Vec<ProtoNodeV17>,
     pub indices: Vec<(Hash256, usize)>,
     pub previous_proposer_boost: ProposerBoost,
 }
 
+impl TryInto<SszContainer> for SszContainerV16 {
+    type Error = Error;
+
+    fn try_into(self) -> Result<SszContainer, Error> {
+        let nodes: Result<Vec<ProtoNodeV17>, Error> =
+            self.nodes.into_iter().map(TryInto::try_into).collect();
+
+        Ok(SszContainer {
+            votes: self.votes,
+            balances: self.balances,
+            prune_threshold: self.prune_threshold,
+            justified_checkpoint: self.justified_checkpoint,
+            finalized_checkpoint: self.finalized_checkpoint,
+            nodes: nodes?,
+            indices: self.indices,
+            previous_proposer_boost: self.previous_proposer_boost,
+        })
+    }
+}
+
+impl Into<SszContainerV16> for SszContainer {
+    fn into(self) -> SszContainerV16 {
+        let nodes = self.nodes.into_iter().map(Into::into).collect();
+
+        SszContainerV16 {
+            votes: self.votes,
+            balances: self.balances,
+            prune_threshold: self.prune_threshold,
+            justified_checkpoint: self.justified_checkpoint,
+            finalized_checkpoint: self.finalized_checkpoint,
+            nodes,
+            indices: self.indices,
+            previous_proposer_boost: self.previous_proposer_boost,
+        }
+    }
+}
+
 impl From<&ProtoArrayForkChoice> for SszContainer {
     fn from(from: &ProtoArrayForkChoice) -> Self {
         let proto_array = &from.proto_array;