OpenSearch Unassigned Shards

How to fix it

// try these in order, the most common fix is first

1. FIX 1Diagnose

   Copy steps
   1. 01GET _cat/shards?v&h=index,shard,prirep,state,unassigned.reason
   2. 02GET _cluster/allocation/explain?pretty
   Did this fix it? Yes No

2. FIX 2Retry failed allocations

   1. 01POST _cluster/reroute?retry_failed=true
   Did this fix it? Yes No

3. FIX 3Unblock allocation

   Copy steps
   1. 01Check cluster.routing.allocation.enable and exclude/require filters in GET _cluster/settings
   2. 02Raise or free disk below the low watermark
   Did this fix it? Yes No

4. FIX 4Do not delete shards blindly

   1. 01Fix the cause so the cluster reassigns by itself; delete an index only when you can recreate it
   Did this fix it? Yes No

Symptoms

_cat/shards shows UNASSIGNED shards and the cluster is yellow or red.

Why it happens

• C-01Disk watermarks reached
• C-02Node left the cluster
• C-03Shard limit per node exceeded
• C-04Allocation disabled or filtering rules
• C-05Failed shard allocation after too many retries

// this guide also covers

• opensearch unassigned shards
• opensearch allocation explain
• opensearch shard not allocated

Other OpenSearch errors

• OpenSearch Cluster Status Red
• OpenSearch Cluster Status Yellow
• OpenSearch High JVM Memory Pressure
• OpenSearch OutOfMemoryError and Circuit Breaker
• OpenSearch Exceeded Maximum Shard Limit
• OpenSearch Index Read-Only: Disk Watermark and ClusterBlockException
• OpenSearch 429 Too Many Requests
• OpenSearch Docker Container Won't Start