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Replica-aware routing public beta
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Replica-aware routing ensures queries access the same ClickHouse replica, preventing errors with temporary tables.
This feature addresses issues with temporary tables and named sessions that previously could not be accessed across different replicas. By maintaining requests on the same replica, it enhances consistency and performance in multi-replica environments. This can be particularly beneficial in use cases requiring read-after-write consistency, such as interactive applications and ETL processes.
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Replica-aware routing routes requests to the same ClickHouse replica to access temporary tables and named sessions.
Users can achieve read-after-write consistency, reading their own writes even before other replicas catch up.
It is particularly useful for maintaining warm caches in replicas, improving performance for repeated workloads.
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The introduction of replica-aware routing in ClickHouse's public beta allows users to ensure their queries consistently hit the same database replica. This is essential for operations involving temporary tables and session-specific data that only exist on the originating replica. It prevents the common issue of queries failing due to the data not being available on other replicas.
To utilize this feature, users need to include specific routing keys in their queries, which can be done via HTTP headers or SNI overrides in native connections. This adds a slight complexity to query construction but is crucial for achieving the desired consistency across sessions. Adoption costs mainly involve the need to update query logic to incorporate these routing keys.
However, replica-aware routing may not be suitable for all scenarios, particularly those where high availability and load balancing across replicas are prioritized over strict consistency. In environments with heavy write loads or where immediate visibility of data across replicas is critical, relying solely on this method could lead to performance trade-offs.
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