Status RED
Severity:
Critical
Elasticsearch Version:
7.x, 8.x
Problem
Cluster health is RED due to unassigned primary shards.
Root Cause
Node failure or disk watermarks exceeded.
How to Detect
Symptoms
- _cluster/health shows red
- Index unavailable for reads/writes
Commands
GET _cluster/health
GET _cat/shards?vRemediation Steps
- Identify unassigned shards
- Free disk space or add node
- Reroute shards manually if required
Prevention
- Set proper disk watermarks
- Enable shard allocation awareness
Production Example
POST _cluster/reroute { ... }