Node not switching to block processing in linea chain

[damian-orzechowski]

Using linea chain, node falls into an infinite loop and fails to switch to block processing after finishing state sync.
The problem seems to be caused by the conditions needed to assume state is available and switch away from state sync in MultiSyncModeSelector. Block headers are downloaded up to head - 32 blocks (FastSyncLag), where head is the block number of our best peer. This sets the best suggested header, which is used as a pivot when setting target block for sync (state ranges and healing TreeSync). That means that at best, the synced state can be head - 32 blocks, but as the head and therefore best header move with the chain, it is almost impossible to have state == head - 32, which is one of the conditions needed to assume state is downloaded and finish StateSync phase.

Screenshots

2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|Snapshot H:12883238 | T:12883271 | B:12874638 | S:12883211 | PV: 12440000 | BP: 12874638 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   BEACON HEADERS      : yes(shouldBeNotInUpdatingPivot), no(shouldBeInBeaconHeaders) 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76| * FAST                : yes(notInUpdatingPivot, notInBeaconModes, postPivotPeerAvailable, notReachedFullSyncTransition, notInAStickyFullSync, notHasJustStartedFullSync, notNeedToWaitForHeaders), no() 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76| * STATE               : yes(fastSyncEnabled, notInUpdatingPivot, hasFastSyncBeenActive, hasAnyPostPivotPeer, notInFastSync||stickyStateNodes, stateNotDownloadedYet, notInAStickyFullSync, notHasJustStartedFullSync, notNeedToWaitForHeaders), no() 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   STATE_NODES         : yes(isInStateSync, snapRangesFinished), no(snapSyncDisabled) 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   SNAP_RANGES         : yes(SnapSyncEnabled, isInStateSync, isCloseToHead), no(snapNotFinished) 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   HEADERS             : yes(notInUpdatingPivot), no(fastBlocksHeadersNotFinished) 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   BODIES              : yes(fastHeadersFinished, stateSyncFinished), no(fastBodiesNotFinished, notInStateSync) 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   RECEIPTS            : yes(fastBodiesFinished, stateSyncFinished), no(fastReceiptsNotFinished, notInStateSync) 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   FULL                : yes(notInUpdatingPivot, notInBeaconModes, desiredPeerKnown, postPivotPeerAvailable, hasFastSyncBeenActive, stateSyncFinished, notNeedToWaitForHeaders), no(notInFastSync, notInStateSync) 
2024-12-04 09:22:00.2179|TRACE|Synchronization.ParallelSync.MultiSyncModeSelector|76|   WAITING FOR BLOCK   : yes(notInBeaconHeaders, postPivotPeerAvailable, hasFastSyncBeenActive), no(inBeaconControl, noDesiredPeerKnown, notInFastSync, notInStateSync) 
2024-12-04 09:22:00.2179|INFO|Synchronization.ParallelSync.MultiSyncModeSelector|76|Changing sync StateNodes to FastSync, StateNodes at block: 12874638 | header: 12883238 | target: 12883271 | peer: 12883271 

[LukaszRozmej]

Not sure if I follow, but can that be solved by making FastSyncLag parametrized in config and decreasing that for Linea?