Data column custody info (#7648)

#7647


  Introduces a new record in the blobs db `DataColumnCustodyInfo`

When `DataColumnCustodyInfo` exists in the db this indicates that a recent cgc change has occurred and/or that a custody backfill sync is currently in progress (custody backfill will be added as a separate PR). When a cgc change has occurred `earliest_available_slot` will be equal to the slot at which the cgc change occured. During custody backfill sync`earliest_available_slot` should be updated incrementally as it progresses.

~~Note that if `advertise_false_custody_group_count` is enabled we do not add a `DataColumnCustodyInfo` record in the db as that would affect the status v2 response.~~
(See comment https://github.com/sigp/lighthouse/pull/7648#discussion_r2212403389)

~~If `DataColumnCustodyInfo` doesn't exist in the db this indicates that we have fulfilled our custody requirements up to the DA window.~~
(It now always exist, and the slot will be set to `None` once backfill is complete)

StatusV2 now uses `DataColumnCustodyInfo` to calculate the `earliest_available_slot` if a `DataColumnCustodyInfo` record exists in the db, if it's `None`, then we return the `oldest_block_slot`.

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -6807,6 +6807,15 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             .map(|duration| (next_digest_epoch, duration))
     }
 
+    /// Update data column custody info with the slot at which cgc was changed.
+    pub fn update_data_column_custody_info(&self, slot: Option<Slot>) {
+        self.store
+            .put_data_column_custody_info(slot)
+            .unwrap_or_else(
+                |e| tracing::error!(error = ?e, "Failed to update data column custody info"),
+            );
+    }
+
     /// This method serves to get a sense of the current chain health. It is used in block proposal
     /// to determine whether we should outsource payload production duties.
     ///

beacon_node/beacon_chain/src/schema_change.rs

@@ -3,6 +3,7 @@ mod migration_schema_v23;
 mod migration_schema_v24;
 mod migration_schema_v25;
 mod migration_schema_v26;
+mod migration_schema_v27;
 
 use crate::beacon_chain::BeaconChainTypes;
 use std::sync::Arc;
@@ -67,6 +68,17 @@ pub fn migrate_schema<T: BeaconChainTypes>(
             let ops = migration_schema_v26::downgrade_from_v26::<T>(db.clone())?;
             db.store_schema_version_atomically(to, ops)
         }
+        (SchemaVersion(26), SchemaVersion(27)) => {
+            // This migration updates the blobs db. The schema version
+            // is bumped inside upgrade_to_v27.
+            migration_schema_v27::upgrade_to_v27::<T>(db.clone())
+        }
+        (SchemaVersion(27), SchemaVersion(26)) => {
+            // Downgrading is essentially a no-op and is only possible
+            // if peer das isn't scheduled.
+            migration_schema_v27::downgrade_from_v27::<T>(db.clone())?;
+            db.store_schema_version_atomically(to, vec![])
+        }
         // Anything else is an error.
         (_, _) => Err(HotColdDBError::UnsupportedSchemaVersion {
             target_version: to,

beacon_node/beacon_chain/src/schema_change/migration_schema_v27.rs

@@ -0,0 +1,26 @@
+use crate::BeaconChainTypes;
+use std::sync::Arc;
+use store::{metadata::SchemaVersion, Error, HotColdDB};
+
+/// Add `DataColumnCustodyInfo` entry to v27.
+pub fn upgrade_to_v27<T: BeaconChainTypes>(
+    db: Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>,
+) -> Result<(), Error> {
+    if db.spec.is_peer_das_scheduled() {
+        db.put_data_column_custody_info(None)?;
+        db.store_schema_version_atomically(SchemaVersion(27), vec![])?;
+    }
+
+    Ok(())
+}
+
+pub fn downgrade_from_v27<T: BeaconChainTypes>(
+    db: Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>,
+) -> Result<(), Error> {
+    if db.spec.is_peer_das_scheduled() {
+        return Err(Error::MigrationError(
+            "Cannot downgrade from v27 if peerDAS is scheduled".to_string(),
+        ));
+    }
+    Ok(())
+}

beacon_node/beacon_chain/src/validator_custody.rs

@@ -217,6 +217,7 @@ impl CustodyContext {
                     new_custody_group_count: updated_cgc,
                     sampling_count: self
                         .num_of_custody_groups_to_sample(Some(effective_epoch), spec),
+                    effective_epoch,
                 });
             }
         }
@@ -287,6 +288,7 @@ impl CustodyContext {
 pub struct CustodyCountChanged {
     pub new_custody_group_count: u64,
     pub sampling_count: u64,
+    pub effective_epoch: Epoch,
 }
 
 /// The custody information that gets persisted across runs.