a race condition in blocks state causes accidental backfilling

[karen-sarkisyan]

In core/src/execution/state.rs there's a race condition when a latest or a finalized block gets pushed into blocks tree.

Each push of a block triggers a check for a need to backfill missed blocks (see push_block() method). There's no intention in helios to backfill blocks at startup, so it starts checking for a need to backfill only when it has at least 2 blocks in state.

However, in case when finalized block is pushed into blocks tree first, and latest block is second, there can be a large gap between these 2 blocks in blocks tree, which is then filled by sending RPC calls.

[sam-ejma081]

Hello, we tried to solve the issue.

This is what we did:

Modified the push_block and push_finalized_block methods to prevent unnecessary backfilling when there's a large gap between finalized and latest blocks. Added a new max_backfill parameter to limit the number of blocks to backfill.

You can review changes in this commit: sam-ejma081@cf26bbe.

Caution

Disclaimer: The concept of solution was created by AI and you should never copy paste this code before you check the correctness of generated code. Solution might not be complete, you should use this code as an inspiration only.

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