1、上机动手实战演练基于_version进行乐观锁并发控制
(1)先构造一条数据出来
PUT /test_index/_doc/7
{
"test_field": "test test"
}
(2)模拟两个客户端,都获取到了同一条数据
GET test_index/_doc/7
{
"_index": "test_index",
"_type": "_doc",
"_id": "7",
"_version": 1,
"found": true,
"_source": {
"test_field": "test test"
}
}
(3)其中一个客户端,先更新了一下这个数据
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/_doc/7?version=1
{
"test_field": "test client 1"
}
报错:
{
"error" : {
"root_cause" : [
{
"type" : "action_request_validation_exception",
"reason" : "Validation Failed: 1: internal versioning can not be used for optimistic concurrency control. Please use `if_seq_no` and `if_primary_term` instead;"
}
],
"type" : "action_request_validation_exception",
"reason" : "Validation Failed: 1: internal versioning can not be used for optimistic concurrency control. Please use `if_seq_no` and `if_primary_term` instead;"
},
"status" : 400
}
旧版本的elasticsearch是用version来解决并发问题,采用乐观锁的方式,比较更新时的version是否相同来决定能不能更新
在新版本es再使用version就会报上述问题,而新版本用的是_seq_no
和_primary_term
两个字段来代替version处理并发问题,在查询文档时,这两个字段会返回。
GET /test_index/_doc/7
{
"_index" : "test_index",
"_type" : "_doc",
"_id" : "7",
"_version" : 4,
"_seq_no" : 4,
"_primary_term" : 1,
"found" : true,
"_source" : {
"test_field" : "test test 1232"
}
}
需要使用 _seq_no
和 _primary_term
两个字段来代替version处理并发问题
PUT /test_index/_doc/7?if_seq_no=4&if_primary_term=1
{
"test_field": "test test dddddddd"
}
使用如下方式,并且 version 值要大于当前 document 的 version 值:
PUT /test_index/_doc/7?version=2&version_type=external
{
"test_field": "test client 1"
}
(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/_doc/7?version=2&version_type=external
{
"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
}
(5)在乐观锁成功阻止并发问题之后,尝试正确的完成更新, 重新获取 document 数据和版本号
GET /test_index/_doc/7
{
"_index": "test_index",
"_type": "_doc",
"_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,修改后,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/_doc/7?version=3&version_type=external
{
"test_field": "test client 2"
}
{
"_index": "test_index",
"_type": "_doc",
"_id": "7",
"_version": 3,
"result": "updated",
"_shards": {
"total": 2,
"successful": 1,
"failed": 0
},
"created": false
}