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nimbus-eth2/beacon_chain/sync
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Jacek Sieka 118840d241
SyncManager cleanups for backfill support (#3189) 
* SyncManager cleanups for backfill support

Cleanups, fixes and simplifications, in anticipation of backfill support
for the `SyncManager`:

* reformat sync progress indicator to show time left and % done more
prominently:
  * old: `sync="sPssPsssss:2:2.4229:00h57m (2706898)"`
  * new: `sync="14d12h31m (0.52%) 1.1378slots/s (wQQQQQDDQQ:1287520)"`
* reset average speed when going out of sync
* pass all block errors to sync manager, including duplicate/unviable
* penalize peers for reporting a head block that is outside of our
expected wall clock time (they're likely on a different network or
trying to disrupt sync)
* remove `SyncFailureKind` (unused)
* remove `inRange` (unused)
* add `Q` for sync queue requests that are in the `SyncQueue` but not
yet in the `BlockProcessor` queue
* update last slot in `SyncQueue` after getting peer status
* fix race condition between `wakeupWaiters` and `resetWait`, where
workers would not be correctly reset if block verification returned a
completed future without event loop
* log syncmanager direction

* Fix ordering issue.
Some of the requests size of which are not equal to `chunkSize` could be processed in wrong order which could lead to sync process freezes.

Co-authored-by: cheatfate <eugene.kabanov@status.im>
2021-12-16 15:57:16 +01:00
..
peer_scores.nim
SyncManager cleanups for backfill support (#3189)
2021-12-16 15:57:16 +01:00
README.md
Consolidate modules by areas [part 1] (#2365)
2021-03-02 11:27:45 +01:00
request_manager.nim
SyncManager cleanups for backfill support (#3189)
2021-12-16 15:57:16 +01:00
sync_manager.nim
SyncManager cleanups for backfill support (#3189)
2021-12-16 15:57:16 +01:00
sync_protocol.nim
Backfill support for ChainDAG (#3171)
2021-12-13 14:36:06 +01:00
sync_queue.nim
SyncManager cleanups for backfill support (#3189)
2021-12-16 15:57:16 +01:00

README.md

Block syncing

This folder holds all modules related to block syncing

Block syncing uses ETH2 RPC protocol.

Reference diagram

Block flow

Eth2 RPC in

Blocks are requested during sync by the SyncManager.

Blocks are received by batch:

  • syncStep(SyncManager, index, peer)
  • in case of success:
    • push(SyncQueue, SyncRequest, seq[SignedBeaconBlock]) is called to handle a successful sync step. It calls validate(SyncQueue, SignedBeaconBlock)` on each block retrieved one-by-one
    • validate only enqueues the block in the SharedBlockQueue AsyncQueue[BlockEntry] but does no extra validation only the GossipSub case
  • in case of failure:
    • push(SyncQueue, SyncRequest) is called to reschedule the sync request.

Every second when sync is not in progress, the beacon node will ask the RequestManager to download all missing blocks currently in quarantaine.

  • via handleMissingBlocks
  • which calls fetchAncestorBlocks
  • which asynchronously enqueue the request in the SharedBlockQueue AsyncQueue[BlockEntry].

The RequestManager runs an event loop:

  • that calls fetchAncestorBlocksFromNetwork
  • which RPC calls peers with beaconBlocksByRoot
  • and calls validate(RequestManager, SignedBeaconBlock) on each block retrieved one-by-one
  • validate only enqueues the block in the AsyncQueue[BlockEntry] but does no extra validation only the GossipSub case

Weak subjectivity sync

Not implemented!

Comments

The validate procedure name for SyncManager and RequestManager as no P2P validation actually occurs.

Sync vs Steady State

During sync:

  • The RequestManager is deactivated
  • The syncManager is working full speed ahead
  • Gossip is deactivated

Bottlenecks during sync

During sync:

  • The bottleneck is clearing the SharedBlockQueue AsyncQueue[BlockEntry] via storeBlock which requires full verification (state transition + cryptography)

Backpressure

The SyncManager handles backpressure by ensuring that current_queue_slot <= request.slot <= current_queue_slot + sq.queueSize * sq.chunkSize.

  • queueSize is -1, unbounded, by default according to comment but all init paths uses 1 (?)
  • chunkSize is SLOTS_PER_EPOCH = 32

However the shared AsyncQueue[BlockEntry] itself is unbounded. Concretely:

  • The shared AsyncQueue[BlockEntry] is bounded for sync
  • The shared AsyncQueue[BlockEntry] is unbounded for validated gossip blocks

RequestManager and Gossip are deactivated during sync and so do not contribute to pressure.