elasticsearch实现乐观锁

迈不过友情╰ 2022-04-25 04:28 271阅读 0赞

elasticsearch的写操作是原子性的，可以通过如下两种方式实现es写操作的乐观锁。

## 基于\_version ##

`version_type`在elasticsearch6.x被移除，故该方法不适用于6.x版本，详见[https://www.elastic.co/guide/en/elasticsearch/reference/6.7/docs-update.html][https_www.elastic.co_guide_en_elasticsearch_reference_6.7_docs-update.html]

PUT /user/user_type/1
    {
      "name": "tom",
      "age": 18,
      "doc_version": 1 // 自定义的文档版本号,用于乐观锁
    }

只更新低版本的记录

PUT /user/user_type/1?version=2&version_type=external_gt
    {
      "name": "tom",
      "age": 18,
      "doc_version": 2
    }

忽略版本号强制更新

PUT /user/user_type/1?version=3&version_type=force
    {
      "name": "tom",
      "age": 18,
      "doc_version": 3
    }

## 基于script ##

PUT /user/user_type/1
    {
      "name": "tom",
      "age": 18,
      "doc_version": 1 
    }

只更新es中`doc_version`版本低的记录

POST /user/user_type/1/_update
    {
      "script": {
        "source": "if(params.doc_force == true || ctx._source.doc_version < params.doc_version){for(entry in params.entrySet()){if (entry.getKey() != 'ctx') ctx._source[entry.getKey()] = entry.getValue();}}else{ctx.op = 'none'}",
        "lang": "painless",
        "params": {
          "name": "tom",
          "age": 19,
          "doc_version": 19
        }
      }
    }

忽略自定义版本号`doc_version`强制更新记录

注：读取`script`中的`params`的值时，需要过滤掉`params.ctx`，原因是es的`painless`脚本会自动向`params`中添加`ctx`，如果不过滤，则上述的更新语法会报如下错误：

{
      "error": {
        "root_cause": [
          {
            "type": "remote_transport_exception",
            "reason": "[0l2AYvx][127.0.0.1:9300][indices:data/write/update[s]]"
          }
        ],
        "type": "illegal_argument_exception",
        "reason": "Iterable object is self-referencing itself"
      },
      "status": 400
    }

详见[https://github.com/elastic/elasticsearch/pull/32096][https_github.com_elastic_elasticsearch_pull_32096]。

[https_www.elastic.co_guide_en_elasticsearch_reference_6.7_docs-update.html]: https://www.elastic.co/guide/en/elasticsearch/reference/6.7/docs-update.html
[https_github.com_elastic_elasticsearch_pull_32096]: https://github.com/elastic/elasticsearch/pull/32096