Elasticsearch Cluster Health Red: How to Fix It

How to fix it

Try these in order — the most common fix is first.

1. 1. Diagnose

   Copy steps
   1. GET _cluster/health?level=indices to find red indices
   2. GET _cat/shards?v and look for UNASSIGNED primaries
   3. GET _cluster/allocation/explain for the failing shard
   Did this fix it? Yes No

2. 2. Bring the missing node back

   Copy steps
   1. Restart or repair the node that left the cluster
   2. After it rejoins, wait for automatic allocation or run POST _cluster/reroute with no body
   Did this fix it? Yes No

3. 3. Recover from a snapshot or reindex

   Copy steps
   1. If the error is no_valid_shard_copy, restore the index from a snapshot, or reindex from the source system
   2. Delete the index only if the data is expendable
   Did this fix it? Yes No

4. 4. Last resort: allocate a primary with data loss

   Copy steps
   1. POST _cluster/reroute with allocate_stale_primary or allocate_empty_primary and accept_data_loss: true
   2. Elastic warns this can overwrite data if the original node later rejoins; use only when recovery is impossible
   Did this fix it? Yes No

Symptoms

GET _cluster/health shows status red; searches on some indices fail or return partial results; Kibana reports shard failures.

Why it happens

• A node holding the only copy of a primary shard is down
• Disk watermark blocked allocation
• Corrupted or lost shard data (no_valid_shard_copy)
• High JVM memory pressure tripping circuit breakers during recovery

This guide also covers

• elasticsearch cluster health red
• elasticsearch red status fix
• elasticsearch primary shard unassigned

Other Elasticsearch errors

• Elasticsearch Cluster Health Yellow: Causes and Fixes
• Elasticsearch Unassigned Shards: Why and How to Fix
• Elasticsearch circuit_breaking_exception: Data Too Large
• Elasticsearch High JVM Memory Pressure and Out of Memory
• Elasticsearch Disk Watermark: Index Read-Only (FORBIDDEN/12)
• Elasticsearch Limit of Total Fields [1000] Exceeded
• Why Is Elasticsearch So Slow? Fixing Slow Searches
• Elasticsearch Cannot Change Field Mapping: Reindex Guide