- green：每个索引的primary shard 和replica 都是active状态，ES集群正常。
- yellow：每个索引的primary shard 是 active状态，但是部分的replica shard 不是active,ES集群可以正常使用。
- red：不是所有索引的primary shard 都是active状态，部分索引数据丢失，集群不可用。
可以通过以下方式查看：
http://127.0.0.1:9200/_cluster/health?pretty#
{
  "cluster_name" : "elasticsearch",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 8,
  "number_of_data_nodes" : 8,
  "active_primary_shards" : 373,
  "active_shards" : 752,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 100.0
}

http://192.168.2.131:9200/_cat/nodes?v&s=ip:desc&h=http,version,jdk,disk.total,disk.used,disk.avail,disk.used_percent,heap.current,heap.percent,heap.max,ram.current,ram.percent,ram.max,master

http://192.168.2.131:9200/_cat/indices?v&s=pri.store.size:desc

http://192.168.2.131:9200/_cat/allocation?v

http://192.168.2.131:9200/_nodes/node131/hot_threads

Curl -u elastic:'password' -XPUT 192.168.2.131:9200/contractcenter/_settings -H 'Content-Type: application/json' -d '{  
 "index.search.slowlog.threshold.query.warn": "5s", 
 "index.search.slowlog.threshold.query.info": "2s",
 "index.search.slowlog.threshold.query.debug": "600ms",
 "index.search.slowlog.threshold.query.trace": "200ms",
 "index.search.slowlog.threshold.fetch.warn": "1s",
 "index.search.slowlog.threshold.fetch.info": "800ms",
 "index.search.slowlog.threshold.fetch.debug": "500ms",
 "index.search.slowlog.threshold.fetch.trace": "10ms",
 "index.search.slowlog.level": "info"
}'

curl -u elastic:'password' -XPOST 'http:// 192.168.2.131:9200/contractcenter/_forcemerge?only_expunge_deletes=true'

http://192.168.2.131:9200/_cat/thread_pool?v

curl -u elastic:'password' -XPOST 'http://192.168.2.131:9200/_cluster/reroute?retry_failed=true'

cluster.routing.allocation.enable参数为 null时，允许进行分片分配；该参数为primaries时，仅允许分配主分片的分片；该参数为none时，禁用所有分片分配，如下所示：
curl -u elastic:'password' -X PUT "192.168.2.131:9200/_cluster/settings" -H 'Content-Type: application/json' -d '{ "persistent": { "cluster.routing.allocation.enable": "none" } }'

curl -u elastic:'password' -XPUT http://192.168.2.131:9200/_cluster/settings?pretty -H 'Content-Type: application/json' -d '
{"transient":{"cluster.routing.allocation.exclude._ip":"192.168.2.132"}}'

http://192.168.2.131:9200/_cat/shards?v&h=n,index,shard,prirep,state,sto,sc,unassigned.reason,unassigned.details
ALLOCATION_FAILED：由于分片分配失败而未分配。
CLUSTER_RECOVERED：由于集群恢复而未分配。 
DANGLING_INDEX_IMPORTED：由于导入了悬空索引导致未分配。 
EXISTING_INDEX_RESTORED：由于恢复为已关闭的索引导致未分配。 
INDEX_CREATED：由于API创建索引而未分配。 
INDEX_REOPENED：由于打开已关闭索引而未分配。 
NEW_INDEX_RESTORED：由于恢复到新索引而未分配。 
NODE_LEFT：由于托管的节点离开集群而未分配。 
REALLOCATED_REPLICA：确定了更好的副本位置，并导致现有副本分配被取消。 
REINITIALIZED：当分片从开始移动回初始化，导致未分配。 
REPLICA_ADDED：由于显式添加副本而未分配。 
REROUTE_CANCELLED：由于显式取消重新路由命令而未分配。

curl -u elastic:'password' -XPOST 'http://192.168.2.131:9200/_cluster/reroute'  -H 'Content-Type: application/json' -d  '{ "commands" : [ { "move" : { "index" : “index", "shard" : 1, "from_node" : "192.168.2.131", "to_node" : "192.168.2.132"
 }
 }
 ]
}'

高水位参数：cluster.routing.allocation.disk.watermark.high
低水位参数：cluster.routing.allocation.disk.watermark.low
实例：调整高水位阈值
curl  -H "Content-Type:application/json" -u elastic -XPUT "http://192.168.2.131:9200/_cluster/settings" -d '{
"transient": {
"cluster.routing.allocation.disk.watermark.high":"95%"
} }'

curl -u elastic:'password' -XPOST 'http://192.168.2.131:9200/_reindex?slices=5&refresh' -H 'Content-Type: application/json' -d {
  "source": {
    "index": “index",
    "size": 5000
  },
  "dest": {
    "index": “index_bak",
  }
}

curl -u elastic:'password' -XPOST 'http://192.168.2.131:9200/_aliases' -H 'Content-Type: application/json' -d '{
    "actions" : [
        { "add" : { "index" : “index01", "alias" : “indexalias" , "is_write_index": true} }
    ]
}'