ES集群分片数据的高可用

集群中的索引主分片和副分片在不同的计算机上，如果某个主分片所在的节点宕机，则原有的某个副分片会提成为主分片继续对外进行服务，如果宕机的节点恢复了服务并加入集群中，该节点主分片会降为副分片，缺少的数据会从别的节点上提升为主分片的分片进行补充。

1. 集群设置索引节点

一个主分片分散到三个节点上，每个节点存在一个副本分片
请求地址：http://localhost:9203/shopping
请求方式：PUT
请求参数：

{
    "settings":{
        "number_of_shards":3,
        "number_of_replicas":1
    }
}

2. 集群新增文档数据

请求地址：http://localhost:9201/shopping/_doc/1
请求方式：POST
请求参数：

{
    "name":"甜瓜"
}

3.查看集群中文档数据分片节点

请求地址：http://localhost:9202/shopping/_search
请求方式：GET
请求参数：

{
    "explain":true,
    "query":{
        "match_all":{}
    }
}

返回结果：

{
    "took": 698,
    "timed_out": false,
    "_shards": {
        "total": 3,
        "successful": 3,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": {
            "value": 5,
            "relation": "eq"
        },
        "max_score": 1.0,
        "hits": [
            {
                "_shard": "[shopping][0]",
                "_node": "_U66vmMhTtCOjJZiBd4g-A",
                "_index": "shopping",
                "_type": "_doc",
                "_id": "5",
                "_score": 1.0,
                "_source": {
                    "name": "葡萄"
                },
                "_explanation": {
                    "value": 1.0,
                    "description": "*:*",
                    "details": []
                }
            },
            {
                "_shard": "[shopping][1]",
                "_node": "ax3r-sCLTHCzJFKGx5XwfA",
                "_index": "shopping",
                "_type": "_doc",
                "_id": "2",
                "_score": 1.0,
                "_source": {
                    "name": "香蕉"
                },
                "_explanation": {
                    "value": 1.0,
                    "description": "*:*",
                    "details": []
                }
            },
            {
                "_shard": "[shopping][1]",
                "_node": "ax3r-sCLTHCzJFKGx5XwfA",
                "_index": "shopping",
                "_type": "_doc",
                "_id": "3",
                "_score": 1.0,
                "_source": {
                    "name": "苹果"
                },
                "_explanation": {
                    "value": 1.0,
                    "description": "*:*",
                    "details": []
                }
            },
            {
                "_shard": "[shopping][1]",
                "_node": "ax3r-sCLTHCzJFKGx5XwfA",
                "_index": "shopping",
                "_type": "_doc",
                "_id": "4",
                "_score": 1.0,
                "_source": {
                    "name": "桔子"
                },
                "_explanation": {
                    "value": 1.0,
                    "description": "*:*",
                    "details": []
                }
            },
            {
                "_shard": "[shopping][2]",
                "_node": "7PtbggywTNmT1Z9AnFZzkg",
                "_index": "shopping",
                "_type": "_doc",
                "_id": "1",
                "_score": 1.0,
                "_source": {
                    "name": "甜瓜"
                },
                "_explanation": {
                    "value": 1.0,
                    "description": "*:*",
                    "details": []
                }
            }
        ]
    }
}

分片0：葡萄（id=5）
分片1：香蕉（id=2），苹果（id=3），桔子（id=4）
分片2：甜瓜（id=1）

4. 让节点9201宕机，查看其分片变化

发现会把9202节点的副分片1提升为主分片1，一会之后会在9202节点上添加副分片0,9203节点添加副分片1.

5. 让节点9201，查看分片变化