ScyllaDB is a high-performance, distributed NoSQL database designed to handle large volumes of data with low latency. It is compatible with Apache Cassandra, offering similar features but with enhanced performance and scalability. ScyllaDB is used for real-time big data applications, providing high throughput and low latency.
One common issue encountered in ScyllaDB is Schema Disagreement. This occurs when nodes in the cluster have different schema versions, leading to inconsistencies in data operations. The symptom is typically observed as an error message indicating schema disagreement when executing queries.
When schema disagreement occurs, you might see an error message like:
SchemaDisagreementException: Schema versions are not in agreement
Schema disagreement happens when nodes in a ScyllaDB cluster do not have the same schema version. This can occur due to network issues, node failures, or when schema changes are not propagated correctly across the cluster. It is crucial to resolve this issue to ensure data consistency and reliable database operations.
To resolve schema disagreement, follow these steps:
Ensure all nodes in the cluster are up and running. Use the nodetool status command to verify the status of each node:
nodetool status
Look for any nodes that are down or have connectivity issues.
Sometimes, schema disagreement resolves itself as nodes synchronize their schema versions. Wait for a few minutes and check if the issue persists.
Examine the logs on each node for any schema-related errors. Logs can provide insights into why schema changes are not being propagated. Check the ScyllaDB logs located at /var/log/scylla/ for any anomalies.
If the issue persists, you may need to force schema synchronization. Restarting the affected nodes can help propagate the correct schema version. Use the following command to restart a node:
sudo systemctl restart scylla-server
For more information on handling schema disagreements in ScyllaDB, refer to the following resources:
By following these steps, you can effectively diagnose and resolve schema disagreement issues in your ScyllaDB cluster, ensuring smooth and consistent database operations.
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