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Fix I/O atomicity issues with checkpoint sync (#2671)

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## Issue Addressed

This PR addresses an issue found by @YorickDowne during testing of v2.0.0-rc.0.

Due to a lack of atomic database writes on checkpoint sync start-up, it was possible for the database to get into an inconsistent state from which it couldn't recover without `--purge-db`. The core of the issue was that the store's anchor info was being stored _before_ the `PersistedBeaconChain`. If a crash occured so that anchor info was stored but _not_ the `PersistedBeaconChain`, then on restart Lighthouse would think the database was unitialized and attempt to compare-and-swap a `None` value, but would actually find the stale info from the previous run.

## Proposed Changes

The issue is fixed by writing the anchor info, the split point, and the `PersistedBeaconChain` atomically on start-up. Some type-hinting ugliness was required, which could possibly be cleaned up in future refactors.
This commit is contained in:
Michael Sproul
2021-10-05 03:53:17 +00:00
parent 28b79084cd
commit ed1fc7cca6
7 changed files with 95 additions and 36 deletions
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2
beacon_node/beacon_chain/src/historical_blocks.rs
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@@ -182,7 +182,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
};
let backfill_complete = new_anchor.block_backfill_complete();
self.store
.compare_and_set_anchor_info(Some(anchor_info), Some(new_anchor))?;
.compare_and_set_anchor_info_with_write(Some(anchor_info), Some(new_anchor))?;
// If backfill has completed and the chain is configured to reconstruct historic states,
// send a message to the background migrator instructing it to begin reconstruction.