數(shù)據(jù)建模實(shí)戰(zhàn)之基于document鎖實(shí)現(xiàn)悲觀鎖并發(fā)控制

1、對document level鎖，詳細(xì)的講解

全局鎖，一次性就鎖整個(gè)index，對這個(gè)index的所有增刪改操作都會(huì)被block住，如果上鎖不頻繁，還可以，比較簡單

細(xì)粒度的一個(gè)鎖，document鎖，顧名思義，每次就鎖你要操作的，你要執(zhí)行增刪改的那些doc，doc鎖了，其他線程就不能對這些doc執(zhí)行增刪改操作了
但是你只是鎖了部分doc，其他線程對其他的doc還是可以上鎖和執(zhí)行增刪改操作的

document鎖，是用腳本進(jìn)行上鎖

POST /fs/lock/1/_update
{
  "upsert": { "process_id": 123 },
  "script": "if ( ctx._source.process_id != process_id ) { assert false }; ctx.op = 'noop';"
  "params": {
    "process_id": 123
  }
}

/fs/lock，是固定的，就是說fs下的lock type，專門用于進(jìn)行上鎖
/fs/lock/id，比如1，id其實(shí)就是你要上鎖的那個(gè)doc的id，代表了某個(gè)doc數(shù)據(jù)對應(yīng)的lock（也是一個(gè)doc）
_update + upsert：執(zhí)行upsert操作

params，里面有個(gè)process_id，process_id，是你的要執(zhí)行增刪改操作的進(jìn)程的唯一id，比如說可以在java系統(tǒng)，啟動(dòng)的時(shí)候，給你的每個(gè)線程都用UUID自動(dòng)生成一個(gè)thread id，你的系統(tǒng)進(jìn)程啟動(dòng)的時(shí)候給整個(gè)進(jìn)程也分配一個(gè)UUID。process_id + thread_id就代表了某一個(gè)進(jìn)程下的某個(gè)線程的唯一標(biāo)識。可以自己用UUID生成一個(gè)唯一ID

process_id很重要，會(huì)在lock中，設(shè)置對對應(yīng)的doc加鎖的進(jìn)程的id，這樣其他進(jìn)程過來的時(shí)候，才知道，這條數(shù)據(jù)已經(jīng)被別人給鎖了

assert false，不是當(dāng)前進(jìn)程加鎖的話，則拋出異常
ctx.op='noop'，不做任何修改

如果該document之前沒有被鎖，/fs/lock/1之前不存在，也就是doc id=1沒有被別人上過鎖; upsert的語法，那么執(zhí)行index操作，創(chuàng)建一個(gè)/fs/lock/id這條數(shù)據(jù)，而且用params中的數(shù)據(jù)作為這個(gè)lock的數(shù)據(jù)。process_id被設(shè)置為123，script不執(zhí)行。這個(gè)時(shí)候象征著process_id=123的進(jìn)程已經(jīng)鎖了一個(gè)doc了。

如果document被鎖了，就是說/fs/lock/1已經(jīng)存在了，代表doc id=1已經(jīng)被某個(gè)進(jìn)程給鎖了。那么執(zhí)行update操作，script，此時(shí)會(huì)比對process_id，如果相同，就是說，某個(gè)進(jìn)程，之前鎖了這個(gè)doc，然后這次又過來，就可以直接對這個(gè)doc執(zhí)行操作，說明是該進(jìn)程之前鎖的doc，則不報(bào)錯(cuò)，不執(zhí)行任何操作，返回success; 如果process_id比對不上，說明doc被其他doc給鎖了，此時(shí)報(bào)錯(cuò)

/fs/lock/1
{
  "process_id": 123
}

POST /fs/lock/1/_update
{
  "upsert": { "process_id": 123 },
  "script": "if ( ctx._source.process_id != process_id ) { assert false }; ctx.op = 'noop';"
  "params": {
    "process_id": 123
  }
}

script：ctx._source.process_id，123
process_id：加鎖的upsert請求中帶過來額proess_id

如果兩個(gè)process_id相同，說明是一個(gè)進(jìn)程先加鎖，然后又過來嘗試加鎖，可能是要執(zhí)行另外一個(gè)操作，此時(shí)就不會(huì)block，對同一個(gè)process_id是不會(huì)block，ctx.op= 'noop'，什么都不做，返回一個(gè)success

如果說已經(jīng)有一個(gè)進(jìn)程加了鎖了

/fs/lock/1
{
  "process_id": 123
}

POST /fs/lock/1/_update
{
  "upsert": { "process_id": 123 },
  "script": "if ( ctx._source.process_id != process_id ) { assert false }; ctx.op = 'noop';"
  "params": {
    "process_id": 234
  }
}

"script": "if ( ctx._source.process_id != process_id ) { assert false }; ctx.op = 'noop';"

ctx._source.process_id：123
process_id: 234

process_id不相等，說明這個(gè)doc之前已經(jīng)被別人上鎖了，process_id=123上鎖了; process_id=234過來再次嘗試上鎖，失敗，assert false，就會(huì)報(bào)錯(cuò)

此時(shí)遇到報(bào)錯(cuò)的process，就應(yīng)該嘗試重新上鎖，直到上鎖成功

有報(bào)錯(cuò)的話，如果有些doc被鎖了，那么需要重試

直到所有鎖定都成功，執(zhí)行自己的操作。。。

釋放所有的鎖

2、上document鎖的完整實(shí)驗(yàn)過程

scripts/judge-lock.groovy: if ( ctx._source.process_id != process_id ) { assert false }; ctx.op = 'noop';

POST /fs/lock/1/_update
{
  "upsert": { "process_id": 123 },
  "script": {
    "lang": "groovy",
    "file": "judge-lock", 
    "params": {
      "process_id": 123
    }
  }
}

{
  "_index": "fs",
  "_type": "lock",
  "_id": "1",
  "_version": 1,
  "result": "created",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  }
}

GET /fs/lock/1
{
  "_index": "fs",
  "_type": "lock",
  "_id": "1",
  "_version": 1,
  "found": true,
  "_source": {
    "process_id": 123
  }
}

POST /fs/lock/1/_update
{
  "upsert": { "process_id": 234 },
  "script": {
    "lang": "groovy",
    "file": "judge-lock", 
    "params": {
      "process_id": 234
    }
  }
}

{
  "error": {
    "root_cause": [
      {
        "type": "remote_transport_exception",
        "reason": "[4onsTYV][127.0.0.1:9300][indices:data/write/update[s]]"
      }
    ],
    "type": "illegal_argument_exception",
    "reason": "failed to execute script",
    "caused_by": {
      "type": "script_exception",
      "reason": "error evaluating judge-lock",
      "caused_by": {
        "type": "power_assertion_error",
        "reason": "assert false\n"
      },
      "script_stack": [],
      "script": "",
      "lang": "groovy"
    }
  },
  "status": 400
}

POST /fs/lock/1/_update
{
  "upsert": { "process_id": 123 },
  "script": {
    "lang": "groovy",
    "file": "judge-lock", 
    "params": {
      "process_id": 123
    }
  }
}

{
  "_index": "fs",
  "_type": "lock",
  "_id": "1",
  "_version": 1,
  "result": "noop",
  "_shards": {
    "total": 0,
    "successful": 0,
    "failed": 0
  }
}

POST /fs/file/1/_update
{
  "doc": {
    "name": "README1.txt"
  }
}

{
  "_index": "fs",
  "_type": "file",
  "_id": "1",
  "_version": 4,
  "result": "updated",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  }
}

POST /fs/_refresh 

GET /fs/lock/_search?scroll=1m
{
  "query": {
    "term": {
      "process_id": 123
    }
  }
}

{
  "_scroll_id": "DnF1ZXJ5VGhlbkZldGNoBQAAAAAAACPkFjRvbnNUWVZaVGpHdklqOV9zcFd6MncAAAAAAAAj5RY0b25zVFlWWlRqR3ZJajlfc3BXejJ3AAAAAAAAI-YWNG9uc1RZVlpUakd2SWo5X3NwV3oydwAAAAAAACPnFjRvbnNUWVZaVGpHdklqOV9zcFd6MncAAAAAAAAj6BY0b25zVFlWWlRqR3ZJajlfc3BXejJ3",
  "took": 51,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 1,
    "max_score": 1,
    "hits": [
      {
        "_index": "fs",
        "_type": "lock",
        "_id": "1",
        "_score": 1,
        "_source": {
          "process_id": 123
        }
      }
    ]
  }
}

PUT /fs/lock/_bulk
{ "delete": { "_id": 1}}

{
  "took": 20,
  "errors": false,
  "items": [
    {
      "delete": {
        "found": true,
        "_index": "fs",
        "_type": "lock",
        "_id": "1",
        "_version": 2,
        "result": "deleted",
        "_shards": {
          "total": 2,
          "successful": 1,
          "failed": 0
        },
        "status": 200
      }
    }
  ]
}

POST /fs/lock/1/_update
{
  "upsert": { "process_id": 234 },
  "script": {
    "lang": "groovy",
    "file": "judge-lock", 
    "params": {
      "process_id": 234
    }
  }
}

process_id=234上鎖就成功了

?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點(diǎn)，簡書系信息發(fā)布平臺，僅提供信息存儲(chǔ)服務(wù)。

推薦閱讀更多精彩內(nèi)容