https://www.elastic.co/guide/en/elasticsearch/guide/current/_cluster_health.html#_drilling_deeper_finding_problematic_indices
通過調用接口查看
GET _cluster/health
1、green：健康
All primary and replica shards are allocated. Your cluster is 100% operational.
2、yellow：至少一個副本不可用
All primary shards are allocated, but at least one replica is missing. No data is missing, so search results will still be complete. However, your high availability is compromised to some degree. If more shards disappear, you might lose data. Think of yellow as a warning that should prompt investigation.
3、red：至少一個分片不可用
At least one primary shard (and all of its replicas) is missing. This means that you are missing data: searches will return partial results, and indexing into that shard will return an exception.