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918121e313
Attempt to fix this error reported by `beaconcha.in` on their Hoodi archive nodes:
> {"code":500,"message":"UNHANDLED_ERROR: DBError(CacheBuildError(BeaconState(MilhouseError(OutOfBoundsIterFrom { index: 1199549, len: 1060000 }))))","stacktraces":[]}
There are only a handful of places where we call `iter_from`.
This one is safe by construction (the check immediately prior ensures `self.pubkeys.len()` is not out of bounds):
cfb1f73310/beacon_node/beacon_chain/src/validator_pubkey_cache.rs (L84-L90)
This one should also be safe, and the indexes used here would not be as large as the ones in the reported error:
cfb1f73310/consensus/state_processing/src/per_epoch_processing/single_pass.rs (L365-L368)
Which leaves one remaining usage which must be the culprit:
cfb1f73310/consensus/types/src/beacon_state.rs (L2109-L2113)
This indexing relies on the invariant that `self.pubkey_cache().len() <= self.validators.len()`. We mostly maintain that invariant, except for in `rebase_caches_on` (fixed in this PR).
The other bug, is that we were calling `rebase_on_finalized` for all "hot" states, which post-v7.1.0 includes states prior to the split which are required by the hdiff grid. This is how we end up calling something like `genesis_state.rebase_on(&split_state)`, which then corrupts the pubkey cache of the genesis state using the newer pubkey cache from the split state.