Resolving Unassigned Shard Issues in ELK: Checking Cluster Health, Deleting Problematic Indices, and Restoring Green Status

ELK log system encountered several indices that could not sync; restarting Elasticsearch did not help, data could be read but not written, due to index issues.

Example error: {"type":"unavailable_shards_exception","reason":"[***_2501][0] primary shard is not active Timeout: [1m], request: [BulkShardRequest [[***_2501][0]] containing [325] requests]"}

1. Check Elasticsearch for many UNASSIGNED indices

2. Delete problematic indices

curl -XDELETE http://192.167.51.8:9200/****_2352

{"acknowledged":true}

3. Verify cluster status becomes green via Cerebro

For unassigned shards, common solutions include restarting the cluster (network issues may affect shard allocation), checking logs for specific errors, and ensuring sufficient disk space.

Step 1: Check cluster health

curl -XGET 'http://localhost:9200/_cluster/health'

Step 2: List all shards

curl -XGET 'http://localhost:9200/_cat/shards'

Step 3: Find unassigned shards

curl -XGET 'http://localhost:9200/_cat/shards' | grep UNASSIGNED

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