Stuck lookup v6

[dapplion]

Issue Addressed

PR

• Prevent sync lookups from reverting to awaiting block #6443

Introduced a regression on the lookup pruning logic. If a lookup loses all peers before the block request downloads the block, it will get stuck. This is a relatively frequent occurrence. This bug will result in occasional warn logs on the user's terminals.

Example case events

• Lookup created for block A, from peer X
• Peer X disconencts, lookup A now has 0 peers
• 10 seconds pass
• drop_lookups_without_peers runs on lookup A
  • has_no_peers returns true
  • elapsed condition returns true
  • is_awaiting_event returns true <- so it doesn't get pruned

is_awaiting_event checks:

• awaiting_parent.is_some() returns false
• self.block_request_state.state.is_awaiting_event() returns false (block awaiting download)
• component_requests is WaitingForBlock, so it returns true <- the bug is here

lighthouse/beacon_node/network/src/sync/block_lookups/single_block_lookup.rs

Lines 174 to 177 in 193c7f8

	// If components are waiting for the block request to complete, here we should
	// check if the`block_request_state.state.is_awaiting_event(). However we already
	// checked that above, so `WaitingForBlock => false` is equivalent.
	ComponentRequests::WaitingForBlock => false,

Proposed Changes

Fix is_awaiting_event logic.

[michaelsproul]

Makes sense to me, and testing has shown that this greatly reduces the frequency of stuck lookups.

[michaelsproul]

@mergify queue

[mergify]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at 775fa67

[jimmygchen]

I think this makes sense.

I wonder if this would drop any lookups that are awaiting processing?

lighthouse/beacon_node/network/src/sync/block_lookups/single_block_lookup.rs

Line 500 in 886d409

State::AwaitingProcess { .. } => false,

[jimmygchen]

This is unlikely an issue - if we do need the block, external events should somehow keep this lookup in place, a single disconnected peer should not affect this.