eth: use the last announced finalized block as the sync ancient limit (#26685)

eth/catalyst/api.go

@@ -237,6 +237,10 @@ func (api *ConsensusAPI) forkchoiceUpdated(update engine.ForkchoiceStateV1, payl
 			log.Warn("Forkchoice requested unknown head", "hash", update.HeadBlockHash)
 			return engine.STATUS_SYNCING, nil
 		}
+		// If the finalized hash is known, we can direct the downloader to move
+		// potentially more data to the freezer from the get go.
+		finalized := api.remoteBlocks.get(update.FinalizedBlockHash)
+
 		// Header advertised via a past newPayload request. Start syncing to it.
 		// Before we do however, make sure any legacy sync in switched off so we
 		// don't accidentally have 2 cycles running.
@@ -244,8 +248,16 @@ func (api *ConsensusAPI) forkchoiceUpdated(update engine.ForkchoiceStateV1, payl
 			merger.ReachTTD()
 			api.eth.Downloader().Cancel()
 		}
-		log.Info("Forkchoice requested sync to new head", "number", header.Number, "hash", header.Hash())
-		if err := api.eth.Downloader().BeaconSync(api.eth.SyncMode(), header); err != nil {
+		context := []interface{}{"number", header.Number, "hash", header.Hash()}
+		if update.FinalizedBlockHash != (common.Hash{}) {
+			if finalized == nil {
+				context = append(context, []interface{}{"finalized", "unknown"}...)
+			} else {
+				context = append(context, []interface{}{"finalized", finalized.Number}...)
+			}
+		}
+		log.Info("Forkchoice requested sync to new head", context...)
+		if err := api.eth.Downloader().BeaconSync(api.eth.SyncMode(), header, finalized); err != nil {
 			return engine.STATUS_SYNCING, err
 		}
 		return engine.STATUS_SYNCING, nil

eth/catalyst/queue.go

@@ -31,9 +31,12 @@ import (
 const maxTrackedPayloads = 10
 
 // maxTrackedHeaders is the maximum number of executed payloads the execution
-// engine tracks before evicting old ones. Ideally we should only ever track the
-// latest one; but have a slight wiggle room for non-ideal conditions.
-const maxTrackedHeaders = 10
+// engine tracks before evicting old ones. These are tracked outside the chain
+// during initial sync to allow ForkchoiceUpdate to reference past blocks via
+// hashes only. For the sync target it would be enough to track only the latest
+// header, but snap sync also needs the latest finalized height for the ancient
+// limit.
+const maxTrackedHeaders = 96
 
 // payloadQueueItem represents an id->payload tuple to store until it's retrieved
 // or evicted.

eth/catalyst/tester.go

@@ -75,7 +75,7 @@ func (tester *FullSyncTester) Start() error {
 				}
 				// Trigger beacon sync with the provided block header as
 				// trusted chain head.
-				err := tester.api.eth.Downloader().BeaconSync(downloader.FullSync, tester.block.Header())
+				err := tester.api.eth.Downloader().BeaconSync(downloader.FullSync, tester.block.Header(), nil)
 				if err != nil {
 					log.Info("Failed to beacon sync", "err", err)
 				}