1.併發控制

es 的併發控制是通過多version來實現的(不清楚樂觀鎖的自己提升去)

2.例項

//建立索引
PUT /test_index/test_type/7
{
  "test_field": "test test"
}

//返回建立結果

GET test_index/test_type/7

{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 1,
  "found": true,
  "_source": {
    "test_field": "test test"
  }
}

******* 根據版本號來更新索引****************
PUT /test_index/test_type/7?version=1 
{
  "test_field": "test client 1"
}

//返回結果
{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 2,
  "result": "updated",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "created": false
}

******另外一個客戶端，嘗試基於version=1的資料去進行修改，同樣帶上version版本號，進行樂觀鎖的併發控制******
PUT /test_index/test_type/7?version=1 
{
  "test_field": "test client 2"
}

{
  "error": {
    "root_cause": [
      {
        "type": "version_conflict_engine_exception",
        "reason": "[test_type][7]: version conflict, current version [2] is different than the one provided [1]",
        "index_uuid": "6m0G7yx7R1KECWWGnfH1sw",
        "shard": "3",
        "index": "test_index"
      }
    ],
    "type": "version_conflict_engine_exception",
    "reason": "[test_type][7]: version conflict, current version [2] is different than the one provided [1]",
    "index_uuid": "6m0G7yx7R1KECWWGnfH1sw",
    "shard": "3",
    "index": "test_index"
  },
  "status": 409
}


******在樂觀鎖成功阻止併發問題之後，嘗試正確的完成更新*********

PUT /test_index/test_type/7?version=2 
{
  "test_field": "test client 2"
}
//返回結果
{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 3,
  "result": "updated",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "created": false
}


 

3.基於external version 進行併發控制

es提供了一個feature，就是說，你可以不同它提供的內部version 版本號進行併發控制。可以基於你自己維護的version進行控制，這樣的話就可以通過自己維護的那個version來控制。

（1）先構造一條資料

PUT /test_index/test_type/8
{
  "test_field": "test"
}

{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "8",
  "_version": 1,
  "result": "created",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "created": true
}

（2）模擬兩個客戶端同時查詢到這條資料

GET /test_index/test_type/8

{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "8",
  "_version": 1,
  "found": true,
  "_source": {
    "test_field": "test"
  }
}
（3）第一個客戶端先進行修改，此時客戶端程式是在自己的資料庫中獲取到了這條資料的最新版本號，比如說是2

PUT /test_index/test_type/8?version=2&version_type=external
{
  "test_field": "test client 1"
}

{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "8",
  "_version": 2,
  "result": "updated",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "created": false
}

（4）模擬第二個客戶端，同時拿到了自己資料庫中維護的那個版本號，也是2，同時基於version=2發起了修改

PUT /test_index/test_type/8?version=2&version_type=external
{
  "test_field": "test client 2"
}

{
  "error": {
    "root_cause": [
      {
        "type": "version_conflict_engine_exception",
        "reason": "[test_type][8]: version conflict, current version [2] is higher or equal to the one provided [2]",
        "index_uuid": "6m0G7yx7R1KECWWGnfH1sw",
        "shard": "1",
        "index": "test_index"
      }
    ],
    "type": "version_conflict_engine_exception",
    "reason": "[test_type][8]: version conflict, current version [2] is higher or equal to the one provided [2]",
    "index_uuid": "6m0G7yx7R1KECWWGnfH1sw",
    "shard": "1",
    "index": "test_index"
  },
  "status": 409
}

（5）在併發控制成功後，重新基於最新的版本號發起更新

GET /test_index/test_type/8

{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "8",
  "_version": 2,
  "found": true,
  "_source": {
    "test_field": "test client 1"
  }
}

PUT /test_index/test_type/8?version=3&version_type=external
{
  "test_field": "test client 2"
}

{
  "_index": "test_index",
  "_type": "test_type",
  "_id": "8",
  "_version": 3,
  "result": "updated",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "created": false
}