ibd: stop header prefix retries when first header fails - #798
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reardencode merged 2 commits intoSep 28, 2026
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we may have an alternative fix for this coming up, but I'll have grok pause and look at yours before continuing. Thank you!!! |
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A headers batch that cannot connect used to search longer prefixes after the full batch failed. The release note records that the search now stops when the first header is rejected. Co-authored-by: Cursor <cursoragent@cursor.com>
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Problem
On mainnet IBD at ~458k, 2,000-header peer events with no accepted prefix blocked the IBD loop for ~12–13 seconds apiece. Instrumentation measured
accepted_headersas the cost, withaccepted=0,stored_prefix=0, one failed full-batch attempt and 10 failed prefix probes. The same window processed block-body events in milliseconds. See #790.Change
After a failed full batch, validate the first header alone before searching for a longer accepted prefix. If that first header fails, no prefix is acceptable; return without the 10 longer probes. If it succeeds, retain its FK and binary-search the remaining prefix exactly as before. No header validation or store format changes.
Reproduction and validation
/ssd/rbitcoindatadir with--milestone=840000: failed 2,000-header batch fell from ~12–13 s / 11 attempts to ~2.3–2.5 s / 2 attempts. Progress checks moved from ~25 s to ~9–12 s during the brief trial; throughput was variable and is not claimed as a sustained A/B improvement. The node has been restored to the original committed INFO binary.cargo fmt --all -- --check;cargo clippy --workspace --all-targets -- -D warnings;cargo test -p rbitcoin-net --lib(646 passed);cargo test --workspace --no-fail-fast --quiet(passed before a final test-only assertion was added); musl Nix build of the live-tested candidate.Follow-up: the first full-batch attempt still costs ~1.1–1.3 s in the live sample; this PR addresses only redundant retries when the first header cannot be accepted.