1、并发冲突问题

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2、图解剖析悲观锁与乐观锁两种并发控制方案

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3、图解Elasticsearch内部如何基于_version进行乐观锁并发控制

（1）_version元数据
在第一次创建document时内部的_version的内部版本号就为1，每次多document进行增删改时,_version就自动加1
在delete之后，在进行put数据，内部版本号还在+1，这就侧面说明，在delete之后，数据并没有被删除， 他的内部_version等信息还存在。
（2）在es 7.9版本，是基于if_seq_no和if_primary_term进行乐观锁并发控制

  1. PUT /bobotest/_doc/5/  
  2. {
  3.   "name": "lisi",
  4.   "desc": "piaoliang de keai de xiaogege111",
  5.   "age": 15,
  6.   "tags":"shuaige"
  7. }
  9. {
  10.   "_index" : "bobotest",
  11.   "_type" : "_doc",
  12.   "_id" : "5",
  13.   "_version" : 2,  #版本号加1
  14.   "_seq_no" : 17,
  15.   "_primary_term" : 1,
  16.   "found" : true,
  17.   "_source" : {
  18.     "name" : "lisi",
  19.     "desc" : "piaoliang de keai de xiaogege111",
  20.     "age" : 15,
  21.     "tags" : "shuaige"
  22.   }
  23. }

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验证
先创建filed=test1,然后修改_version=1 filed=test2 后修改_version=2 filed=test3

  1. #创建document
  2. PUT /bobotest/_doc/7/
  3. {
  4.   "filed": "test1"
  5. }
  6. {
  7.   "_index" : "bobotest",
  8.   "_type" : "_doc",
  9.   "_id" : "7",
  10.   "_version" : 1,
  11.   "result" : "created",
  12.   "_shards" : {
  13.     "total" : 2,
  14.     "successful" : 1,
  15.     "failed" : 0
  16.   },
  17.   "_seq_no" : 19,
  18.   "_primary_term" : 1
  19. }
  20. #修改if_seq_no=19&if_primary_term=1   "filed": "test3"
  21. PUT /bobotest/_doc/7?if_seq_no=19&if_primary_term=1
  22. {
  23.   "filed": "test3"
  24. }
  25. #修改if_seq_no=20&if_primary_term=1   "filed": "test3"
  26. PUT /bobotest/_doc/7?if_seq_no=20&if_primary_term=1
  27. {
  28.   "filed": "test4"
  29. }
  31. 正确顺序: test1  -->test3-->test4

并发时

  1. test4和test3同时更新
  2. 则 test1 -->test3
  3. PUT /bobotest/_doc/7?if_seq_no=21&if_primary_term=1  #后改的先到
  4. {
  5.   "filed": "test4"
  6. }
  9. PUT /bobotest/_doc/7?if_seq_no=21&if_primary_term=1 #先改的后到
  10. {
  11.   "filed": "test6"
  12. }
  14. #产生错误，抛弃
  15. {
  16.   "error" : {
  17.     "root_cause" : [
  18.       {
  19.         "type" : "version_conflict_engine_exception",
  20.         "reason" : "[7]: version conflict, required seqNo [22], primary term [1]. current document has seqNo [23] and primary term [1]",
  21.         "index_uuid" : "tdMcqHK5ReOYmOAxPWoqUQ",
  22.         "shard" : "0",
  23.         "index" : "bobotest"
  24.       }
  25.     ],
  26.     "type" : "version_conflict_engine_exception",
  27.     "reason" : "[7]: version conflict, required seqNo [22], primary term [1]. current document has seqNo [23] and primary term [1]",
  28.     "index_uuid" : "tdMcqHK5ReOYmOAxPWoqUQ",
  29.     "shard" : "0",
  30.     "index" : "bobotest"
  31.   },
  32.   "status" : 409
  33. }
  34. #重新get if_seq_no和_primary_term的信息。
  35. GET /bobotest/_doc/7
  36. {
  37.   "_index" : "bobotest",
  38.   "_type" : "_doc",
  39.   "_id" : "7",
  40.   "_version" : 5,
  41.   "_seq_no" : 23,
  42.   "_primary_term" : 1,
  43.   "found" : true,
  44.   "_source" : {
  45.     "filed" : "test4"
  46.   }
  47. }
  48. #带上_seq_no=23和_primary_term=1进行修改
  49. PUT /bobotest/_doc/7?if_seq_no=23&if_primary_term=1
  50. {
  51.   "filed": "test6"
  52. }
  53. {
  54.   "_index" : "bobotest",
  55.   "_type" : "_doc",
  56.   "_id" : "7",
  57.   "_version" : 6,
  58.   "result" : "updated",
  59.   "_shards" : {
  60.     "total" : 2,
  61.     "successful" : 1,
  62.     "failed" : 0
  63.   },
  64.   "_seq_no" : 24,
  65.   "_primary_term" : 1
  66. }

4、external version并发版本控制

https://www.elastic.co/guide/en/elasticsearch/reference/7.1/docs-index_.html#_version_types
在es 7.9版本，index的内部版本并发控制改为_seq_no和_primary_term
但是如果使用external 版本控制，还是使用原先的方式_version &version_type=external
_version 必须>内部_version 的版本号

  1. （1）创建索引
  2. PUT /liang/_doc/1
  3. {
  4.   "filed": "test1"
  5. }
  6. {
  7.   "_index" : "liang",
  8.   "_type" : "_doc",
  9.   "_id" : "1",
  10.   "_version" : 1,
  11.   "result" : "created",
  12.   "_shards" : {
  13.     "total" : 2,
  14.     "successful" : 1,
  15.     "failed" : 0
  16.   },
  17.   "_seq_no" : 0,
  18.   "_primary_term" : 1
  19. }
  21. (2)带入版本进行修改_version 必须>内部_version 的版本号
  22. PUT /liang/_doc/1?version=2&version_type=external
  23. {
  24.   "filed": "test2"
  25. }
  26. {
  27.   "_index" : "liang",
  28.   "_type" : "_doc",
  29.   "_id" : "1",
  30.   "_version" : 2,
  31.   "result" : "updated",
  32.   "_shards" : {
  33.     "total" : 2,
  34.     "successful" : 1,
  35.     "failed" : 0
  36.   },
  37.   "_seq_no" : 1,
  38.   "_primary_term" : 1
  39. }
  40. (3)使用客户端1更新此version=2版本的数据
  42. PUT /liang/_doc/1?version=2&version_type=external
  43. {
  44.   "filed": "test2"
  45. }
  46. {
  47.   "_index" : "liang",
  48.   "_type" : "_doc",
  49.   "_id" : "1",
  50.   "_version" : 3,
  51.   "result" : "updated",
  52.   "_shards" : {
  53.     "total" : 2,
  54.     "successful" : 1,
  55.     "failed" : 0
  56.   },
  57.   "_seq_no" : 2,
  58.   "_primary_term" : 1
  59. }
  60. （4）使用客户端2更新version=2版本的数据(由于两个客户端同时更新，所以版本号一致)
  61. PUT /liang/_doc/1?version=2&version_type=external
  62. {
  63.   "filed": "test3"
  64. }
  65. {
  66.   "error" : {
  67.     "root_cause" : [
  68.       {
  69.         "type" : "version_conflict_engine_exception",
  70.         "reason" : "[1]: version conflict, current version [3] is higher or equal to the one provided [2]",
  71.         "index_uuid" : "Vs-63nbZT8qDPo2MCJ43xg",
  72.         "shard" : "0",
  73.         "index" : "liang"
  74.       }
  75.     ],
  76.     "type" : "version_conflict_engine_exception",
  77.     "reason" : "[1]: version conflict, current version [3] is higher or equal to the one provided [2]",
  78.     "index_uuid" : "Vs-63nbZT8qDPo2MCJ43xg",
  79.     "shard" : "0",
  80.     "index" : "liang"
  81.   },
  82.   "status" : 409
  83. }
  84. （5）出现错误，重新get ，进行更新
  85. GET /liang/_doc/1
  86. {
  87.   "_index" : "liang",
  88.   "_type" : "_doc",
  89.   "_id" : "1",
  90.   "_version" : 3,
  91.   "_seq_no" : 2,
  92.   "_primary_term" : 1,
  93.   "found" : true,
  94.   "_source" : {
  95.     "filed" : "test3"
  96.   }
  97. }
  98. version=4&version_type=external中version必须要比_version大
  99. PUT /liang/_doc/1?version=4&version_type=external
  100. {
  101.   "filed": "test3"
  102. }
  103. {
  104.   "_index" : "liang",
  105.   "_type" : "_doc",
  106.   "_id" : "1",
  107.   "_version" : 4,
  108.   "result" : "updated",
  109.   "_shards" : {
  110.     "total" : 2,
  111.     "successful" : 1,
  112.     "failed" : 0
  113.   },
  114.   "_seq_no" : 3,
  115.   "_primary_term" : 1
  116. }