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https://issues.apache.org/jira/browse/CASSGO-104?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Raj Ummadisetty reassigned CASSGO-104:
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Assignee: Raj Ummadisetty
> TokenAwareHostPolicy does not populate replica maps for non-default keyspaces
> -----------------------------------------------------------------------------
>
> Key: CASSGO-104
> URL: https://issues.apache.org/jira/browse/CASSGO-104
> Project: Apache Cassandra Go driver
> Issue Type: Bug
> Reporter: Raj Ummadisetty
> Assignee: Raj Ummadisetty
> Priority: Normal
> Time Spent: 20m
> Remaining Estimate: 0h
>
> h3. Problem:
> When a session is created with keyspace (e.g., {color:#0747a6}ks1{color}) but
> queries are executed against a different keyspace (e.g.,
> {color:#00875a}SELECT * FROM ks2.table{color}), the TokenAwareHostPolicy
> fails to perform token-aware routing for the non-default keyspace. This
> occurs because the replica map (meta.replicas) is only populated for the
> session's default keyspace.
> This is a follow-up to issue ([GitHub
> #1621|https://github.com/apache/cassandra-gocql-driver/issues/1621]). While
> [PR #1714|https://github.com/apache/cassandra-gocql-driver/pull/1714] fixed
> the keyspace extraction from prepared statements, it did not address the
> underlying issue of populating replica information for non-default keyspaces.
> h3. Impact:
> * Ineffective replica shuffling: Even when ShuffleReplicas() is enabled, all
> queries to non-default keyspaces go to the primary replica
> * Creates uneven load distribution across the cluster
> h3. Steps to Reproduce:
>
> {code:java}
> // Create session with keyspace ks1
> cluster := gocql.NewCluster("127.0.0.1")
> cluster.Keyspace = "ks1"
> cluster.PoolConfig.HostSelectionPolicy =
> gocql.TokenAwareHostPolicy(gocql.RoundRobinHostPolicy(),gocql.ShuffleReplicas))
> session, _ := cluster.CreateSession()
> defer session.Close()
> // Query keyspace ks2
> stmt := "SELECT * FROM ks2.table WHERE id = ?"
> // This query will always be routed to primary replica
> query := session.Query(stmt, someID)
> {code}
>
> h3. Root Cause:
> In policies.go, the Pick() method looks up replicas:
> [ht :=
> meta.replicas[keyspace].replicasFor(token)|https://github.com/apache/cassandra-gocql-driver/blob/f1e31a58f7e0c25e58e2e2a0a0c6de358e643e8b/policies.go#L615]
> However, meta.replicas[keyspace] is nil for any keyspace except the session's
> default keyspace
> h3. Proposed Solution
> Implement lazy loading of replica maps in the Pick() method:
> 1. When replicas are not found for a keyspace, call a new
> ensureReplicasForKeyspace() method
> 2. This method uses double-checked locking to populate the replica map
> on-demand
> 3. Subsequent queries to the same keyspace use the cached replica information
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