Elasticsearch系统学习-ES并发控制

Posted 2022-09-23 hujinzhong

一、ES并发控制原理

1.1、ES并发冲突问题

1.2、悲观锁与乐观锁并发控制图解

ES内部基于_version进行乐观锁并发控制：

二、并发控制实践

2.1、基于_version进行乐观锁并发控制

1）构建数据

PUT /test_index/test_type/7

  "test_field": "test test"



  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 1,
  "result": "created",
  "_shards": 
    "total": 2,
    "successful": 1,
    "failed": 0
  ,
  "created": true

2）模拟两个客户端，都获取了同一条数据

GET /test_index/test_type/7


  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 1,   #此时版本号是1
  "found": true,
  "_source": 
    "test_field": "test test"
  

3）模拟一个客户端，先更新了这个数据

同时带上数据的版本号，确保说，es中的数据的版本号，跟客户端中的数据的版本号是相同的，才能修改

PUT /test_index/test_type/7?version=1

  "test_field": "test client 1"



  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 2,   #此时实际版本号已经变成2了
  "result": "updated",
  "_shards": 
    "total": 2,
    "successful": 1,
    "failed": 0
  ,
  "created": false

4）另外一个客户端，尝试基于version=1的数据去进行修改，同样带上version版本号，进行乐观锁的并发控制

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]",   #版本冲突
        "index_uuid": "6t1NqhChSpyuYY7m-Eq2jA",
        "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": "6t1NqhChSpyuYY7m-Eq2jA",
    "shard": "3",
    "index": "test_index"
  ,
  "status": 409

5）在乐观锁成功阻止并发问题之后，尝试正确的完成更新

首先获取正确的版本号

GET /test_index/test_type/7


  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 2,
  "found": true,
  "_source": 
    "test_field": "test client 1"
  

基于最新的数据和版本号，去进行修改，带上最新的版本号，可能这个步骤会需要反复执行好几次，才能成功，特别是在多线程并发更新同一条数据很频繁的情况下

PUT /test_index/test_type/7?version=2

  "test_field": "test client 2"



  "_index": "test_index",
  "_type": "test_type",
  "_id": "7",
  "_version": 3,   #修改成功，版本号再次更改
  "result": "updated",
  "_shards": 
    "total": 2,
    "successful": 1,
    "failed": 0
  ,
  "created": false