ScyllaDB is a high-performance, distributed NoSQL database designed to handle large volumes of data with minimal latency. It is compatible with Apache Cassandra and offers features such as automatic sharding, high availability, and horizontal scalability. ScyllaDB is particularly well-suited for real-time big data applications.
In a ScyllaDB cluster, you may encounter a situation where two nodes have the same token, leading to a NodeTokenCollision. This issue manifests as inconsistent data distribution and potential data loss, as the token ring is disrupted.
The ScyllaDB architecture relies on a token ring to distribute data evenly across nodes. Each node is assigned a unique token range, ensuring that data is partitioned correctly. A NodeTokenCollision occurs when two nodes are mistakenly assigned the same token, causing them to overlap in the token ring. This overlap can lead to data inconsistencies and operational issues.
The primary cause of a token collision is a misconfiguration during node setup or scaling operations. This can happen if tokens are manually assigned without ensuring their uniqueness or if there is an error in the token allocation process.
To resolve a NodeTokenCollision, follow these steps to reassign tokens and restore the integrity of the token ring:
First, identify the nodes with colliding tokens. You can use the ScyllaDB nodetool command to list the tokens assigned to each node:
nodetool ring
Review the output to locate nodes with overlapping token ranges.
Once you have identified the nodes with token collisions, you need to reassign tokens to ensure uniqueness. This can be done by decommissioning one of the colliding nodes and re-adding it with a new token. Use the following commands:
nodetool decommission
After decommissioning, edit the node's configuration to assign a new token. Then, restart the node to rejoin the cluster:
scylla --options "--new-token="
After reassigning tokens, verify that the token distribution is correct and there are no overlaps. Use the nodetool command again:
nodetool ring
Ensure that each node has a unique token range.
For more information on managing tokens in ScyllaDB, refer to the official ScyllaDB Documentation. Additionally, you can explore the Nodetool Command Reference for detailed command usage.
By following these steps, you can effectively resolve a NodeTokenCollision and maintain a healthy ScyllaDB cluster.
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