创建名为 test_index的索引 ：

PUT test_index

注意，PUT test_index和 PUT /test_index效果是一样的。
响应：

{
  "acknowledged" : true,
  "shards_acknowledged" : true,
  "index" : "test_index"
}

查询索引信息：

GET test_index

响应：

{
  "test_index" : {
    "aliases" : { },
    "mappings" : { },
    "settings" : {
      "index" : {
        "creation_date" : "1597456553836",
        "number_of_shards" : "1",
        "number_of_replicas" : "1",
        "uuid" : "b3GPz-gCRgmdpgcgEELY2A",
        "version" : {
          "created" : "7080099"
        },
        "provided_name" : "test_index"
      }
    }
  }
}

可以看到，分片数量number_of_shards 为1，副本数量为number_of_replicas 1 。

修改副本数量

请求：

PUT test_index/_settings
{
  "index" : {
    "number_of_replicas" : 3
  }
}

响应：

{
  "acknowledged" : true
}

注意，当副本创建完成后（可能耗时很长），才会响应。如果耗时很长，可以不用等待响应。过一段时间后去查询索引信息确认即可。

修改分片数量
分片数量，必须在索引创建时指定，创建后无法修改。尝试修改时会报错：

请求

PUT test_index/_settings
{
  "index" : {
    "number_of_shards" : 3
  }
}

响应

{
 "error" : {
   "root_cause" : [
     {
       "type" : "illegal_argument_exception",
       "reason" : "Can't update non dynamic settings [[index.number_of_shards]] for open indices [[test_index/b3GPz-gCRgmdpgcgEELY2A]]"
     }
   ],
   "type" : "illegal_argument_exception",
   "reason" : "Can't update non dynamic settings [[index.number_of_shards]] for open indices [[test_index/b3GPz-gCRgmdpgcgEELY2A]]"
 },
 "status" : 400
}

创建索引时指定分片数量、副本数量

删除之前创建的索引：

DELETE test_index

重新创建 test_index索引：

PUT test_index
{
  "settings" : {
    "index" : {
      "number_of_shards" : 3,
      "number_of_replicas" : 1
    }
  }
}

响应：

{
  "acknowledged" : true,
  "shards_acknowledged" : true,
  "index" : "test_index"
}

查看索引信息：

请求

GET test_index

响应

{
 "test_index" : {
   "aliases" : { },
   "mappings" : { },
   "settings" : {
     "index" : {
       "creation_date" : "1597456553836",
       "number_of_shards" : "1",
       "number_of_replicas" : "1",
       "uuid" : "b3GPz-gCRgmdpgcgEELY2A",
       "version" : {
         "created" : "7080099"
       },
       "provided_name" : "test_index"
     }
   }
 }
}

给索引设置别名

POST _aliases
{
  "actions": [
    {
      "add": {
        "index": "test_index",
        "alias": "test_index_aliasname"
      }
    }
  ]
}