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Jacek Sieka 23eea197f6
Implement split preset/config support (#2710) 
* Implement split preset/config support

This is the initial bulk refactor to introduce runtime config values in
a number of places, somewhat replacing the existing mechanism of loading
network metadata.

It still needs more work, this is the initial refactor that introduces
runtime configuration in some of the places that need it.

The PR changes the way presets and constants work, to match the spec. In
particular, a "preset" now refers to the compile-time configuration
while a "cfg" or "RuntimeConfig" is the dynamic part.

A single binary can support either mainnet or minimal, but not both.
Support for other presets has been removed completely (can be readded,
in case there's need).

There's a number of outstanding tasks:

* `SECONDS_PER_SLOT` still needs fixing
* loading custom runtime configs needs redoing
* checking constants against YAML file

* yeerongpilly support

`build/nimbus_beacon_node --network=yeerongpilly --discv5:no --log-level=DEBUG`

* load fork epoch from config

* fix fork digest sent in status
* nicer error string for request failures
* fix tools

* one more

* fixup

* fixup

* fixup

* use "standard" network definition folder in local testnet

Files are loaded from their standard locations, including genesis etc,
to conform to the format used in the `eth2-networks` repo.

* fix launch scripts, allow unknown config values

* fix base config of rest test

* cleanups

* bundle mainnet config using common loader
* fix spec links and names
* only include supported preset in binary

* drop yeerongpilly, add altair-devnet-0, support boot_enr.yaml
 		2021-07-12 15:01:38 +02:00
..
README.md Consolidate modules by areas [part 1] (#2365) 2021-03-02 11:27:45 +01:00
request_manager.nim clean up block processing (#2610) 2021-05-28 19:34:00 +03:00
sync_manager.nim clean up block processing (#2610) 2021-05-28 19:34:00 +03:00
sync_protocol.nim Implement split preset/config support (#2710) 2021-07-12 15:01:38 +02:00

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.