Fix metadata synchronization issues in Snuba migrations for multi-replica/shard ClickHouse clusters #6826
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…d shards This commit introduces a retry mechanism to handle synchronization errors in migrations caused by outdated metadata in ClickHouse replicas. Additionally, it ensures DROP TABLE operations use SYNC. These changes address one of the critical issues in the Snuba migration system, improving stability and reliability when working with ClickHouse clusters.
evanh
reviewed
Jan 27, 2025
| super().execute() | ||
| break | ||
| except Exception as e: | ||
| if i and 'Metadata on replica is not up to date with common metadata in Zookeeper' in str(e): |
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I believe the exception that is returned here will have an error code in it. Could you change this to match on the code instead of the string?
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Problem:
The Snuba migration system encountered significant stability issues when running migrations in ClickHouse clusters with multiple replicas and shards. Synchronization errors, particularly due to outdated metadata on zookeeper, frequently caused migrations to fail or require manual intervention.
Solution:
Retry Mechanism: Added a RetryOnSyncError class that retries operations up to 30 seconds when synchronization errors are encountered (Metadata is not up to date). This mechanism has been integrated into critical migration operations (AddColumn, DropColumn, ModifyColumn, etc.) to handle transient synchronization issues gracefully.
DROP TABLE with SYNC: Updated DROP TABLE operations to include the SYNC keyword, ensuring consistency.
Impact:
These changes significantly enhance the robustness of the Snuba migration system when operating in distributed ClickHouse environments with complex replication setups. By automatically handling synchronization delays, the risk of migration failures is reduced, minimizing operational overhead and downtime.
Testing:
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