make indexer handle null block hashes

[fbac]

Before the future release 0.2.0 the block_hash is not stored in database. In future releases we're using the block_hash to check for reorgs.

There's a rare corner case where the indexer tries to retrieve a block hash that happens to be null, in that case we should skip it and check for reorgs later in the chain.

In the case when a reorg happens later in the chain, and the reorg handler algorithm determines the reorg happened in a range we don't have any data about, then the indexer should simply start indexing from 0, as it's the safest option.

Summary by CodeRabbit

• Bug Fixes
  • Enhanced reorganization detection by adding safeguards to handle scenarios with missing block data.
  • Improved error handling to prevent issues during blockchain updates.

[coderabbitai]

Walkthrough

The pull request introduces two modifications focused on enhancing error handling related to blockchain reorganization detection. In the pkg/indexer/indexer.go file, the indexLogs function now checks that storedBlockHash is not nil before comparing it with the on-chain block’s hash. In the pkg/indexer/reorgHandler.go file, the FindReorgPoint method gains a new conditional branch that handles cases where the oldest block’s hash is nil by retrieving block number zero and updating canonicality within a specific range. No changes have been made to exported or public entities.

Changes

File	Summary
pkg/indexer/indexer.go	Added a check in indexLogs to ensure storedBlockHash is not nil before comparing with the on-chain block hash to prevent nil dereference errors.
pkg/indexer/reorgHandler.go	Introduced a new conditional in FindReorgPoint to handle a nil BlockHash for oldestBlock by retrieving block zero via client.BlockByNumber and updating canonicality.

Sequence Diagram(s)

sequenceDiagram
    participant Caller
    participant ReorgHandler
    participant Client
    participant QueryUpdater

    Caller->>ReorgHandler: Invoke FindReorgPoint(oldestBlock)
    alt oldestBlock.BlockHash is nil
        ReorgHandler->>Client: BlockByNumber(0)
        Client-->>ReorgHandler: block0
        ReorgHandler->>QueryUpdater: UpdateBlocksCanonicalityInRange(0, detectedAt)
        QueryUpdater-->>ReorgHandler: Confirmation
        ReorgHandler-->>Caller: Return block0.Hash
    else BlockHash is present
        ReorgHandler-->>Caller: Proceed with existing logic
    end

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Suggested reviewers

• mkysel

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Reviewing files that changed from the base of the PR and between 8e4dada and 2014b6c.

📒 Files selected for processing (2)

• pkg/indexer/indexer.go (1 hunks)
• pkg/indexer/reorgHandler.go (1 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (1)

• GitHub Check: Test (Node)

🔇 Additional comments (2)

pkg/indexer/reorgHandler.go (1)

72-89: LGTM! The null block hash handling looks good.

The implementation correctly handles the case where the oldest block's hash is null by:

1. Retrieving block 0 from the chain
2. Updating canonicality for the affected range
3. Returning block 0's hash as the reorg point

This aligns with the PR objective of deferring reorg checks when encountering null block hashes.

pkg/indexer/indexer.go (1)

303-304: LGTM! The null check is a necessary safeguard.

The addition of the null check for storedBlockHash prevents potential nil pointer dereferences during block hash comparison and aligns with the changes in reorgHandler.go.

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[mkysel]

LGTM. Do you wanna absorb #471 into this and merge both together?