Final answer:
To remove unassigned shards in Elasticsearch, identify the cause using appropriate APIs, reroute the shards using the _cluster/reroute API if necessary, free up disk space, or add more nodes, and monitor the cluster after taking action.
Step-by-step explanation:
To remove unassigned shards in Elasticsearch, you usually need to address the reason why the shards are unassigned in the first place. Common reasons include a node that has left the cluster without properly reallocating its shards, or a disk on a node that has run out of space. Here is a general approach to help with unassigned shards:
- Identify why the shards are unassigned using the Elasticsearch _cluster/health or _cat/shards APIs.
- If a node has left the cluster, and the shards were not reallocated, you can use the _cluster/reroute API to manually allocate them to a different node.
- In cases where a disk is full, free up space or add more nodes to the cluster to accommodate the unassigned shards.
- Temporary allocation failures due to network issues or node restarts usually resolve on their own once the cluster state stabilizes.
- Always monitor the Elasticsearch cluster status after taking any action to ensure the problem is resolved.
It is crucial to address the underlying issue causing the unassigned shards to prevent it from happening again in the future.