feat(fault-proof): add state backup/restore to challenger#848
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fakedev9999 wants to merge 5 commits into
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feat(fault-proof): add state backup/restore to challenger#848fakedev9999 wants to merge 5 commits into
fakedev9999 wants to merge 5 commits into
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The challenger re-syncs all games from index 0 on every restart. On chains with high dispute game volume, this means thousands of redundant on-chain calls before the challenger becomes operational. Add ChallengerBackup for persisting cursor + game cache to disk. On restart, state is restored from backup and forward sync resumes from cursor+1 instead of 0. Unlike the proposer, the challenger keeps forward sync (not backward) because it must monitor ALL games without gaps — missing one means an invalid game goes unchallenged. Closes #841
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- Use CHALLENGER_BACKUP_PATH env var (not BACKUP_PATH) to avoid collision with proposer when both run on same machine - Extract save_json() helper to deduplicate atomic write logic between ProposerBackup and ChallengerBackup - Use spawn_blocking for challenger backup I/O to avoid blocking the async runtime during fsync
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Summary
Add state backup/restore to the challenger, mirroring the proposer's backup mechanism (#756). The challenger re-syncs all games from index 0 on every restart — on chains with thousands of games this means thousands of redundant on-chain calls.
With backup enabled, the cursor and game cache persist to disk. On restart, state is restored and forward sync resumes from
cursor+1instead of 0.Why forward sync (not backward like proposer)
The proposer uses backward sync (latest → anchor) because it only needs recent games for canonical head calculation. The challenger must monitor all IN_PROGRESS games — missing one means an invalid game goes unchallenged. Forward sync guarantees no gaps.
The problem was "cursor resets to 0 on restart", not "forward direction". Backup solves this.
What's backed up
cursor(U256) — highest processed factory indexgames(Vec<Game>) — cached game metadataOn restore,
sync_state()step 2 recomputes allshould_attempt_to_*flags from on-chain state, so stale flags from backup are overwritten before any action.Closes #841
Configuration
Set
CHALLENGER_BACKUP_PATHin.env.challenger(optional):Note: uses a distinct env var from the proposer's
BACKUP_PATHto avoid conflicts when both run on the same machine.Test plan
cargo check -p op-succinct-fpcargo test -p op-succinct-fp --lib— 47/47 pass (includes new schema guard)cargo test --test backup -p op-succinct-fp— 21/21 pass (12 proposer + 9 challenger)cargo fmt/cargo clippyclean