Lookup sync with blocks_by_head#9541
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Block lookups now prefer peers that advertise beacon_blocks_by_head and fetch the block (plus a run of its ancestors) via that protocol, falling back to beacon_blocks_by_root otherwise. on_block_download_response now receives a Vec of blocks; the ancestors beyond the requested root are not yet consumed (header-backfill step).
Implement Serialize for the rpc Protocol enum (as its canonical name) so PeerInfo.supported_protocols is surfaced in the peers API, matching how subnet fields are serialized, rather than skipped.
Move the identify protocol-id parsing into a standalone rpc_protocol_from_id function and add a unit test covering ReqResp, non-ReqResp, and unknown protocol ids.
- AncestorBlocks::from_vec consumes an iterator (no remove(0)) - BlocksByHeadRequestItems::add uses if-let instead of match - reduce rpc_protocol_from_id test to two cases
- Split block_lookup_request send paths into send_block_by_root_request
and send_blocks_by_head, both taking the selected PeerId
- on_{single_block,blocks_by_head}_response return AncestorBlocks so the
sync manager does no transformation
- query peer_supports_blocks_by_head after selection instead of carrying it
Add the beacon_blocks_by_head support flag as the first tuple element and keep unstable's .min()/peer-in-tuple shape instead of restructuring.
Strictly de-prioritize peers already at MAX_CONCURRENT_REQUESTS for the protocol we would use (by_head if supported, else by_root), counting only that protocol's in-flight requests per the spec's per-protocol-ID limit. Expose MAX_CONCURRENT_REQUESTS and add ActiveRequests::active_request_count_of_peer.
Build per-peer blocks_by_root / blocks_by_head count maps once instead of scanning per candidate peer; gate selection on the relevant protocol's count >= MAX_CONCURRENT_REQUESTS.
…ctors - send_block_by_root_request/send_blocks_by_head take lookup_id, allocate their own req_id, and return it - replace the two per-peer count helpers with an ActiveRequestsPerPeer struct exposing at_concurrency_limit(peer) - give AncestorBlocks from_single/from_vec constructors and inline into_ancestor_blocks into the response handlers
…elper get_parent_import_status now reports an already-imported block (genesis, or a finalized block whose parent was pruned) as having an imported parent, so a lookup for such an anchor is processed rather than awaiting a missing parent. Block lookups use cx.conflicts_with_finality (returning a reason String) to drop blocks at/below finalization that are off the finalized chain.
Pass known_blocks down search_parent_of_child -> new_current_lookup -> on_lookup_result so every ancestor seeded from a single beacon_blocks_by_head response is served from the cache, rather than only the first parent level.
- size PARENT_DEPTH_TOLERANCE to BLOCKS_BY_HEAD_REQUEST_COUNT + 1 so one by-head batch can seed a full chain without tripping the depth limit - rig: serve BlocksByHead (walk parent chain) and a peerdb test setter + rig helper to mark a peer as advertising beacon_blocks_by_head - add a test asserting a 32-block chain resolves with 1 by-head request and 0 blocks-by-root, all blocks cached
is_parent_imported now also returns true when the block is itself in fork choice (contains_block), covering genesis and finalized blocks whose anchor proto-node isn't queryable via get_block. This lets a lookup for such a block be processed instead of dropped as conflicting with finality.
Serve beacon_blocks_by_head in the test rig (honouring the empty/wrong-block failure strategies), add a PeerSupport enum threaded into TestRig::default / new_after_fulu, and nest the depth macro so every lookup test runs as a by_root and a by_head variant.
… fetch a batch A lookup that nothing is waiting on is a lone island and requests a small count (4); once a child is awaiting it the lookup is part of a chain proven deep and requests a large batch (32). Derived from the lookup graph at creation, no escalation state. Tune the counts against mainnet metrics.
The subject (beacon_blocks_by_head) now lives in the type name, so the variants read clearly on their own instead of the ambiguous DoesNotSupport.
SingleLookupRequestState now records the peers that failed a download for the request, and block_lookup_request de-prioritizes them in peer selection (just below the concurrency-limit check). This stops a faulty by_head peer from being re-picked on every retry in a mixed peer set, letting the lookup fall back to a by_root peer instead of exhausting its attempts and dropping. Found in review.
Add a rig test asserting a faulty by_head peer's failed download forces the retry to fall back to a by_root peer (1 BlocksByHead + 1 BlocksByRoot, lookup succeeds). Also restore the set_peer_supports_by_head helper name, mangled by the earlier ByHeadSupport rename.
# Conflicts: # beacon_node/network/src/sync/block_lookups/single_block_lookup.rs # beacon_node/network/src/sync/manager.rs # beacon_node/network/src/sync/network_context.rs # beacon_node/network/src/sync/tests/lookups.rs # beacon_node/network/src/sync/tests/range.rs
…chor handling into get_parent_import_status - Remove the out-of-scope failed_peers peer-fallback (block lookups no longer de-prioritize peers that failed a download); it can be a separate PR. - Reject a downloaded block more than SLOT_IMPORT_TOLERANCE ahead of the current slot before creating a parent lookup, so a peer can't make us walk ancestors or force range sync to a bogus future head (cx.block_too_far_in_future). - Move the genesis/anchor 'block is itself in fork choice' case into get_parent_import_status via a proto-less ParentImportStatus::AlreadyImported, so is_parent_imported is a plain matches!.
dapplion
added
ready-for-review
Revert the consensus-side move from the previous commit: get_parent_import_status returns to pure parent-only semantics (no AlreadyImported variant) and block_verification.rs is restored byte-identical to upstream. The genesis/anchor 'block is itself imported' case lives only in the sync-facing is_parent_imported via '|| contains_block', so consensus block-import paths are untouched.
…aker, finality uses Failed, lookup tidy-ups - SyncRequestId::BlocksByHead uses a tuple variant. - Drop the per-peer request-count tiebreaker from lookup peer selection (and the now-unused active_request_count_by_peer helper). - Reuse LookupRequestError::Failed for finality-conflicting blocks; remove the unused ConflictsWithFinality variant. - Collect known ancestors via iterator; tidy two comments.
…tream is_parent_imported goes back to the upstream-pure wrapper of get_parent_import_status (no contains_block, no block hashing on the consensus block-verification path). The genesis/anchor case (a looked-up block already in fork choice, or whose parent was pruned by finalization) is handled in the lookup eager path via block_is_known_to_fork_choice, keyed on the root the lookup already holds.
- libp2p_peers_supporting_blocks_by_head: connected peers advertising the protocol,
counted alongside the other per-peer gauges.
- sync_blocks_by_head_requested_ancestors: histogram of the requested-ancestor count.
- sync_lookups_known_parent_reused_total: blocks reused from a prior by-head response
to seed a parent lookup instead of re-downloading (KnownParents optimization).
(by-head request timings already exist via sync_rpc_request_duration_sec{protocol}.)
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Issue Addressed
Part of tree sync, #7678 the consumer + requester side of
beacon_blocks_by_head. The responder landed in #9237; this is the other half.What do we gain with this PR?
Given a capable
by_headpeer, lookup sync discovers the common ancestor of an unknown block much faster: requiring up to 32 times less roundtrips.Proposed Changes
by_headresponse is delivered asAncestorBlocks { first_block, ancestor_blocks }; the ancestors are cached and threaded through parent-lookup creation, so a single request resolves the chain with zero follow-up downloads.by_head-capable peers. Block lookups pick aby_headpeer when one is available and otherwise fall back toby_root.The whole block-lookup test suite runs against both
by_root- andby_head-capable peers (the rig servesbeacon_blocks_by_head), plus dedicated tests for the count escalation and the peer-fallback-on-failure behaviour.AI disclosure
Original design by hand, completed by Claude (Opus 4.8), reviewed line by line.