{"id":5097,"date":"2021-02-24T18:30:16","date_gmt":"2021-02-24T10:30:16","guid":{"rendered":"https:\/\/damogame.cn\/wordpress\/?p=5097"},"modified":"2021-02-24T18:30:16","modified_gmt":"2021-02-24T10:30:16","slug":"tikv-%e6%ba%90%e7%a0%81%e8%a7%a3%e6%9e%90%e7%b3%bb%e5%88%97-placement-driver","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/5097","title":{"rendered":"TiKV \u6e90\u7801\u89e3\u6790\u7cfb\u5217\u2014\u2014Placement Driver"},"content":{"rendered":"
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\u539f\u6587\u5730\u5740<\/a><\/p>\n

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<\/div>\n<\/div>\n<\/div>\n
<\/div>\n<\/header>\n
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\u672c\u7cfb\u5217\u6587\u7ae0\u4e3b\u8981\u9762\u5411 TiKV \u793e\u533a\u5f00\u53d1\u8005\uff0c\u91cd\u70b9\u4ecb\u7ecd TiKV \u7684\u7cfb\u7edf\u67b6\u6784\uff0c\u6e90\u7801\u7ed3\u6784\uff0c\u6d41\u7a0b\u89e3\u6790\u3002\u76ee\u7684\u662f\u4f7f\u5f97\u5f00\u53d1\u8005\u9605\u8bfb\u4e4b\u540e\uff0c\u80fd\u5bf9 TiKV \u9879\u76ee\u6709\u4e00\u4e2a\u521d\u6b65\u4e86\u89e3\uff0c\u66f4\u597d\u7684\u53c2\u4e0e\u8fdb\u5165 TiKV \u7684\u5f00\u53d1\u4e2d\u3002
\nTiKV \u662f\u4e00\u4e2a\u5206\u5e03\u5f0f\u7684 KV \u7cfb\u7edf\uff0c\u5b83\u91c7\u7528 Raft \u534f\u8bae\u4fdd\u8bc1\u6570\u636e\u7684\u5f3a\u4e00\u81f4\u6027\uff0c\u540c\u65f6\u4f7f\u7528 MVCC + 2PC \u7684\u65b9\u5f0f\u5b9e\u73b0\u4e86\u5206\u5e03\u5f0f\u4e8b\u52a1\u7684\u652f\u6301\u3002
\n\u672c\u6587\u4e3a\u672c\u7cfb\u5217\u6587\u7ae0\u7b2c\u4e09\u8282\u3002<\/p>\n

\u4ecb\u7ecd<\/h2>\n

Placement Driver (\u540e\u7eed\u4ee5 PD \u7b80\u79f0) \u662f TiDB \u91cc\u9762\u5168\u5c40\u4e2d\u5fc3\u603b\u63a7\u8282\u70b9\uff0c\u5b83\u8d1f\u8d23\u6574\u4e2a\u96c6\u7fa4\u7684\u8c03\u5ea6\uff0c\u8d1f\u8d23\u5168\u5c40 ID \u7684\u751f\u6210\uff0c\u4ee5\u53ca\u5168\u5c40\u65f6\u95f4\u6233 TSO \u7684\u751f\u6210\u7b49\u3002PD \u8fd8\u4fdd\u5b58\u7740\u6574\u4e2a\u96c6\u7fa4 TiKV \u7684\u5143\u4fe1\u606f\uff0c\u8d1f\u8d23\u7ed9 client \u63d0\u4f9b\u8def\u7531\u529f\u80fd\u3002<\/p>\n

\u4f5c\u4e3a\u4e2d\u5fc3\u603b\u63a7\u8282\u70b9\uff0cPD \u901a\u8fc7\u96c6\u6210\u00a0etcd<\/a>\u00a0\uff0c\u81ea\u52a8\u7684\u652f\u6301 auto failover\uff0c\u65e0\u9700\u62c5\u5fc3\u5355\u70b9\u6545\u969c\u95ee\u9898\u3002\u540c\u65f6\uff0cPD \u4e5f\u901a\u8fc7 etcd \u7684 raft\uff0c\u4fdd\u8bc1\u4e86\u6570\u636e\u7684\u5f3a\u4e00\u81f4\u6027\uff0c\u4e0d\u7528\u62c5\u5fc3\u6570\u636e\u4e22\u5931\u7684\u95ee\u9898\u3002<\/p>\n

\u5728\u67b6\u6784\u4e0a\u9762\uff0cPD \u6240\u6709\u7684\u6570\u636e\u90fd\u662f\u901a\u8fc7 TiKV \u4e3b\u52a8\u4e0a\u62a5\u83b7\u77e5\u7684\u3002\u540c\u65f6\uff0cPD \u5bf9\u6574\u4e2a TiKV \u96c6\u7fa4\u7684\u8c03\u5ea6\u7b49\u64cd\u4f5c\uff0c\u4e5f\u53ea\u4f1a\u5728 TiKV \u53d1\u9001 heartbeat \u547d\u4ee4\u7684\u7ed3\u679c\u91cc\u9762\u8fd4\u56de\u76f8\u5173\u7684\u547d\u4ee4\uff0c\u8ba9 TiKV \u81ea\u884c\u53bb\u5904\u7406\uff0c\u800c\u4e0d\u662f\u4e3b\u52a8\u53bb\u7ed9 TiKV \u53d1\u547d\u4ee4\u3002\u8fd9\u6837\u8bbe\u8ba1\u4e0a\u9762\u5c31\u975e\u5e38\u7b80\u5355\uff0c\u6211\u4eec\u5b8c\u5168\u53ef\u4ee5\u8ba4\u4e3a PD \u662f\u4e00\u4e2a\u65e0\u72b6\u6001\u7684\u670d\u52a1\uff08\u5f53\u7136\uff0cPD \u4ecd\u7136\u4f1a\u5c06\u4e00\u4e9b\u4fe1\u606f\u6301\u4e45\u5316\u5230 etcd\uff09\uff0c\u6240\u6709\u7684\u64cd\u4f5c\u90fd\u662f\u88ab\u52a8\u89e6\u53d1\uff0c\u5373\u4f7f PD \u6302\u6389\uff0c\u65b0\u9009\u51fa\u7684 PD leader \u4e5f\u80fd\u7acb\u523b\u5bf9\u5916\u670d\u52a1\uff0c\u65e0\u9700\u8003\u8651\u4efb\u4f55\u4e4b\u524d\u7684\u4e2d\u95f4\u72b6\u6001\u3002<\/p>\n

\u521d\u59cb\u5316<\/h2>\n

PD \u96c6\u6210\u4e86 etcd\uff0c\u6240\u4ee5\u901a\u5e38\uff0c\u6211\u4eec\u9700\u8981\u542f\u52a8\u81f3\u5c11\u4e09\u4e2a\u526f\u672c\uff0c\u624d\u80fd\u4fdd\u8bc1\u6570\u636e\u7684\u5b89\u5168\u3002\u73b0\u9636\u6bb5 PD \u6709\u96c6\u7fa4\u542f\u52a8\u65b9\u5f0f\uff0cinitial-cluster \u7684\u9759\u6001\u65b9\u5f0f\u4ee5\u53ca join \u7684\u52a8\u6001\u65b9\u5f0f\u3002<\/p>\n

\u5728\u7ee7\u7eed\u4e4b\u524d\uff0c\u6211\u4eec\u9700\u8981\u4e86\u89e3\u4e0b etcd \u7684\u7aef\u53e3\uff0c\u5728 etcd \u91cc\u9762\uff0c\u9ed8\u8ba4\u8981\u76d1\u542c 2379 \u548c 2380 \u4e24\u4e2a\u7aef\u53e3\u30022379 \u4e3b\u8981\u662f etcd \u7528\u6765\u5904\u7406\u5916\u90e8\u8bf7\u6c42\u7528\u7684\uff0c\u800c 2380 \u5219\u662f etcd peer \u4e4b\u95f4\u76f8\u4e92\u901a\u4fe1\u7528\u7684\u3002<\/p>\n

\u5047\u8bbe\u73b0\u5728\u6211\u4eec\u6709\u4e09\u4e2a pd\uff0c\u5206\u522b\u4e3a pd1\uff0cpd2\uff0cpd3\uff0c\u5206\u522b\u5728 host1\uff0chost2\uff0chost3 \u4e0a\u9762\u3002<\/p>\n

\u5bf9\u4e8e\u9759\u6001\u521d\u59cb\u5316\uff0c\u6211\u4eec\u76f4\u63a5\u5728\u4e09\u4e2a PD \u542f\u52a8\u7684\u65f6\u5019\uff0c\u7ed9 initial-cluster \u8bbe\u7f6e pd1=http:\/\/<\/span>host1:2380<\/span><\/a>,pd2=http:\/\/<\/span>host2:2380<\/span><\/a>,pd3=http:\/\/<\/span>host3:2380<\/span><\/a>\u3002<\/p>\n

\u5bf9\u4e8e\u52a8\u6001\u521d\u59cb\u5316\uff0c\u6211\u4eec\u5148\u542f\u52a8 pd1\uff0c\u7136\u540e\u542f\u52a8 pd2\uff0c\u52a0\u5165\u5230 pd1 \u7684\u96c6\u7fa4\u91cc\u9762\uff0cjoin \u8bbe\u7f6e\u4e3a pd1=http:\/\/<\/span>host1:2379<\/span><\/a>\u3002\u7136\u540e\u542f\u52a8 pd3\uff0c\u52a0\u5165\u5230 pd1\uff0cpd2 \u5f62\u6210\u7684\u96c6\u7fa4\u91cc\u9762\uff0c join \u8bbe\u7f6e\u4e3a pd1=http:\/\/<\/span>host1:2379<\/span><\/a>\u3002<\/p>\n

\u53ef\u4ee5\u770b\u5230\uff0c\u9759\u6001\u521d\u59cb\u5316\u548c\u52a8\u6001\u521d\u59cb\u5316\u5b8c\u5168\u8d70\u7684\u662f\u4e24\u4e2a\u7aef\u53e3\uff0c\u800c\u4e14\u8fd9\u4e24\u4e2a\u662f\u4e92\u65a5\u7684\uff0c\u4e5f\u5c31\u662f\u6211\u4eec\u53ea\u80fd\u4f7f\u7528\u4e00\u79cd\u65b9\u5f0f\u6765\u521d\u59cb\u5316\u96c6\u7fa4\u3002etcd \u672c\u8eab\u53ea\u652f\u6301 initial-cluster \u7684\u65b9\u5f0f\uff0c\u4f46\u4e3a\u4e86\u65b9\u4fbf\uff0cPD \u540c\u65f6\u4e5f\u63d0\u4f9b\u4e86 join \u7684\u65b9\u5f0f\u3002<\/p>\n

join \u4e3b\u8981\u662f\u7528\u4e86 etcd \u81ea\u8eab\u63d0\u4f9b\u7684 member \u76f8\u5173 API\uff0c\u5305\u62ec add member\uff0clist member \u7b49\uff0c\u6240\u4ee5\u6211\u4eec\u4f7f\u7528 2379 \u7aef\u53e3\uff0c\u56e0\u4e3a\u9700\u8981\u5c06\u547d\u4ee4\u53d1\u5230 etcd \u53bb\u6267\u884c\u3002\u800c initial-cluster \u5219\u662f etcd \u81ea\u8eab\u7684\u521d\u59cb\u5316\u65b9\u5f0f\uff0c\u6240\u4ee5\u4f7f\u7528\u7684 2380 \u7aef\u53e3\u3002<\/p>\n

\u76f8\u6bd4\u4e8e initial-cluster\uff0cjoin \u9700\u8981\u8003\u8651\u975e\u5e38\u591a\u7684 case\uff08\u5728 server\/join.go prepareJoinCluster \u51fd\u6570\u91cc\u9762\u6709\u8be6\u7ec6\u7684\u89e3\u91ca\uff09\uff0c\u4f46 join \u7684\u4f7f\u7528\u975e\u5e38\u81ea\u7136\uff0c\u540e\u7eed\u6211\u4eec\u4f1a\u8003\u8651\u53bb\u6389 initial-cluster \u7684\u521d\u59cb\u5316\u65b9\u6848\u3002<\/p>\n

\u9009\u4e3e<\/h2>\n

\u5f53 PD \u542f\u52a8\u4e4b\u540e\uff0c\u6211\u4eec\u5c31\u9700\u8981\u9009\u51fa\u4e00\u4e2a leader \u5bf9\u5916\u63d0\u4f9b\u670d\u52a1\u3002\u867d\u7136 etcd \u81ea\u8eab\u4e5f\u6709 raft leader\uff0c\u4f46\u6211\u4eec\u8fd8\u662f\u89c9\u5f97\u4f7f\u7528\u81ea\u5df1\u7684 leader\uff0c\u4e5f\u5c31\u662f PD \u7684 leader \u8ddf etcd \u81ea\u5df1\u7684 leader \u662f\u4e0d\u4e00\u6837\u7684\u3002<\/p>\n

\u5f53 PD \u542f\u52a8\u4e4b\u540e\uff0cLeader \u7684\u9009\u4e3e\u5982\u4e0b\uff1a<\/p>\n

    \n
  1. \u68c0\u67e5\u5f53\u524d\u96c6\u7fa4\u662f\u4e0d\u662f\u6709 leader\uff0c\u5982\u679c\u6709 leader\uff0c\u5c31 watch \u8fd9\u4e2a leader\uff0c\u53ea\u8981\u53d1\u73b0 leader \u6389\u4e86\uff0c\u5c31\u91cd\u65b0\u5f00\u59cb 1\u3002<\/li>\n
  2. \u5982\u679c\u6ca1\u6709 leader\uff0c\u5f00\u59cb campaign\uff0c\u521b\u5efa\u4e00\u4e2a Lessor\uff0c\u5e76\u4e14\u901a\u8fc7 etcd \u7684\u4e8b\u52a1\u673a\u5236\u5199\u5165\u76f8\u5173\u4fe1\u606f\uff0c\u5982\u4e0b\uff1a\n
    \n
    \/\/ Create a lessor. \r\nctx, cancel := context.WithTimeout(s.client.Ctx(), requestTimeout)\r\nleaseResp, err := lessor.Grant(ctx, s.cfg.LeaderLease)\r\ncancel()\r\n\r\n\/\/ The leader key must not exist, so the CreateRevision is 0.\r\nresp, err := s.txn().\r\n    If(clientv3.Compare(clientv3.CreateRevision(leaderKey), \"=\", 0)).\r\n    Then(clientv3.OpPut(leaderKey, s.leaderValue, clientv3.WithLease(clientv3.LeaseID(leaseResp.ID)))).\r\n    Commit()<\/code><\/pre>\n<\/div>\n
    \u5982\u679c leader key \u7684 CreateRevision \u4e3a 0\uff0c\u8868\u660e\u5176\u4ed6 PD \u8fd8\u6ca1\u6709\u5199\u5165\uff0c\u90a3\u4e48\u6211\u5c31\u53ef\u4ee5\u5c06\u6211\u81ea\u5df1\u7684 leader \u76f8\u5173\u4fe1\u606f\u5199\u5165\uff0c\u540c\u65f6\u4f1a\u5e26\u4e0a\u4e00\u4e2a Lease\u3002\u5982\u679c\u4e8b\u52a1\u6267\u884c\u5931\u8d25\uff0c\u8868\u660e\u5176\u4ed6\u7684 PD \u5df2\u7ecf\u6210\u4e3a\u4e86 leader\uff0c\u90a3\u4e48\u5c31\u91cd\u65b0\u56de\u5230 1\u3002<\/li>\n
  3. \u6210\u4e3a leader \u4e4b\u540e\uff0c\u6211\u4eec\u5bf9\u5b9a\u671f\u8fdb\u884c\u4fdd\u6d3b\u5904\u7406:\n
    \n
    \/\/ Make the leader keepalived.\r\nch, err := lessor.KeepAlive(s.client.Ctx(), clientv3.LeaseID(leaseResp.ID))\r\nif err != nil {\r\n    return errors.Trace(err)\r\n}<\/code><\/pre>\n<\/div>\n
    \u5f53 PD \u5d29\u6e83\uff0c\u539f\u5148\u5199\u5165\u7684 leader key \u4f1a\u56e0\u4e3a lease \u5230\u671f\u800c\u81ea\u52a8\u5220\u9664\uff0c\u8fd9\u6837\u5176\u4ed6\u7684 PD \u5c31\u80fd watch \u5230\uff0c\u91cd\u65b0\u5f00\u59cb\u9009\u4e3e\u3002<\/li>\n
  4. \u521d\u59cb\u5316 raft cluster\uff0c\u4e3b\u8981\u662f\u4ece etcd \u91cc\u9762\u91cd\u65b0\u8f7d\u5165\u96c6\u7fa4\u7684\u5143\u4fe1\u606f\u3002\u62ff\u5230\u6700\u65b0\u7684 TSO \u4fe1\u606f\uff1a\n
    \n
    \/\/ Try to create raft cluster.\r\nerr = s.createRaftCluster()\r\nif err != nil {\r\n    return errors.Trace(err)\r\n}\r\n\r\nlog.Debug(\"sync timestamp for tso\")\r\nif err = s.syncTimestamp(); err != nil {\r\n    return errors.Trace(err)\r\n}<\/code><\/pre>\n<\/div>\n<\/li>\n
  5. \u6240\u6709\u505a\u5b8c\u4e4b\u540e\uff0c\u5f00\u59cb\u5b9a\u671f\u66f4\u65b0 TSO\uff0c\u76d1\u542c lessor \u662f\u5426\u8fc7\u671f\uff0c\u4ee5\u53ca\u5916\u9762\u662f\u5426\u4e3b\u52a8\u9000\u51fa\uff1a\n
    \n
    for {\r\n    select {\r\n    case _, ok := <-ch:\r\n        if !ok {\r\n            log.Info(\"keep alive channel is closed\")\r\n            return nil\r\n        }\r\n    case <-tsTicker.C:\r\n        if err = s.updateTimestamp(); err != nil {\r\n            return errors.Trace(err)\r\n        }\r\n    case <-s.client.Ctx().Done():\r\n        return errors.New(\"server closed\")\r\n    }\r\n}<\/code><\/pre>\n<\/div>\n<\/li>\n<\/ol>\n
    TSO<\/h3>\n
    \u524d\u9762\u6211\u4eec\u8bf4\u5230\u4e86 TSO\uff0cTSO \u662f\u4e00\u4e2a\u5168\u5c40\u7684\u65f6\u95f4\u6233\uff0c\u5b83\u662f TiDB \u5b9e\u73b0\u5206\u5e03\u5f0f\u4e8b\u52a1\u7684\u57fa\u77f3\u3002\u6240\u4ee5\u5bf9\u4e8e PD \u6765\u8bf4\uff0c\u6211\u4eec\u9996\u5148\u8981\u4fdd\u8bc1\u5b83\u80fd\u5feb\u901f\u5927\u91cf\u7684\u4e3a\u4e8b\u52a1\u5206\u914d TSO\uff0c\u540c\u65f6\u4e5f\u9700\u8981\u4fdd\u8bc1\u5206\u914d\u7684 TSO \u4e00\u5b9a\u662f\u5355\u8c03\u9012\u589e\u7684\uff0c\u4e0d\u53ef\u80fd\u51fa\u73b0\u56de\u9000\u7684\u60c5\u51b5\u3002<\/p>\n
    TSO \u662f\u4e00\u4e2a int64 \u7684\u6574\u5f62\uff0c\u5b83\u7531 physical time + logical time \u4e24\u4e2a\u90e8\u5206\u7ec4\u6210\u3002Physical time \u662f\u5f53\u524d unix time \u7684\u6beb\u79d2\u65f6\u95f4\uff0c\u800c logical time \u5219\u662f\u4e00\u4e2a\u6700\u5927 1 << 18 \u7684\u8ba1\u6570\u5668\u3002\u4e5f\u5c31\u662f\u8bf4 1ms\uff0cPD \u6700\u591a\u53ef\u4ee5\u5206\u914d 262144 \u4e2a TSO\uff0c\u8fd9\u4e2a\u80fd\u6ee1\u8db3\u7edd\u5927\u591a\u6570\u60c5\u51b5\u4e86\u3002<\/p>\n
    \u5bf9\u4e8e TSO \u7684\u4fdd\u5b58\u4e8e\u5206\u914d\uff0cPD \u4f1a\u505a\u5982\u4e0b\u5904\u7406\uff1a<\/p>\n
      \n
    1. \u5f53 PD \u6210\u4e3a leader \u4e4b\u540e\uff0c\u4f1a\u4ece etcd \u4e0a\u9762\u83b7\u53d6\u4e0a\u4e00\u6b21\u4fdd\u5b58\u7684\u65f6\u95f4\uff0c\u5982\u679c\u53d1\u73b0\u672c\u5730\u7684\u65f6\u95f4\u6bd4\u8fd9\u4e2a\u5927\uff0c\u5219\u4f1a\u7ee7\u7eed\u7b49\u5f85\u76f4\u5230\u5f53\u524d\u7684\u65f6\u95f4\u5927\u4e8e\u8fd9\u4e2a\u503c\uff1a\n
      \n
      last, err := s.loadTimestamp()\r\nif err != nil {\r\n    return errors.Trace(err)\r\n}\r\n\r\nvar now time.Time\r\n\r\nfor {\r\n    now = time.Now()\r\n    if wait := last.Sub(now) + updateTimestampGuard; wait > 0 {\r\n        log.Warnf(\"wait %v to guarantee valid generated timestamp\", wait)\r\n        time.Sleep(wait)\r\n        continue\r\n    }\r\n    break\r\n}<\/code><\/pre>\n<\/div>\n<\/li>\n
    2. \u5f53 PD \u80fd\u5206\u914d TSO \u4e4b\u540e\uff0c\u9996\u5148\u4f1a\u5411 etcd \u7533\u8bf7\u4e00\u4e2a\u6700\u5927\u7684\u65f6\u95f4\uff0c\u8b6c\u5982\uff0c\u5047\u8bbe\u5f53\u524d\u65f6\u95f4\u662f t1\uff0c\u6bcf\u6b21\u6700\u591a\u80fd\u7533\u8bf7 3s \u7684\u65f6\u95f4\u7a97\u53e3\uff0cPD \u4f1a\u5411 etcd \u4fdd\u5b58 t1 + 3s \u7684\u65f6\u95f4\u503c\uff0c\u7136\u540e PD \u5c31\u80fd\u5728\u5185\u5b58\u91cc\u9762\u76f4\u63a5\u4f7f\u7528\u8fd9\u4e00\u6bb5\u65f6\u95f4\u7a97\u53e3.\u5f53\u5f53\u524d\u7684\u65f6\u95f4 t2 \u5927\u4e8e t1 + 3s \u4e4b\u540e\uff0cPD \u5c31\u4f1a\u5728\u5411 etcd \u7ee7\u7eed\u66f4\u65b0\u4e3a t2 + 3s\uff1a\n
      \n
      if now.Sub(s.lastSavedTime) >= 0 {\r\n    last := s.lastSavedTime\r\n    save := now.Add(s.cfg.TsoSaveInterval.Duration)\r\n    if err := s.saveTimestamp(save); err != nil {\r\n        return errors.Trace(err)\r\n    }\r\n}<\/code><\/pre>\n<\/div>\n
      \u8fd9\u4e48\u5904\u7406\u7684\u597d\u5904\u5728\u4e8e\uff0c\u5373\u4f7f PD \u5f53\u6389\uff0c\u65b0\u542f\u52a8\u7684 PD \u4e5f\u4f1a\u4ece\u4e0a\u4e00\u6b21\u4fdd\u5b58\u7684\u6700\u5927\u7684\u65f6\u95f4\u4e4b\u540e\u5f00\u59cb\u5206\u914d TSO\uff0c\u4e5f\u5c31\u662f 1 \u5904\u7406\u7684\u60c5\u51b5\u3002<\/li>\n
    3. \u56e0\u4e3a PD \u5728\u5185\u5b58\u91cc\u9762\u4fdd\u5b58\u4e86\u4e00\u4e2a\u53ef\u5206\u914d\u7684\u65f6\u95f4\u7a97\u53e3\uff0c\u6240\u4ee5\u5916\u9762\u8bf7\u6c42 TSO \u7684\u65f6\u5019\uff0cPD \u80fd\u76f4\u63a5\u5728\u5185\u5b58\u91cc\u9762\u8ba1\u7b97 TSO \u5e76\u8fd4\u56de\u3002\n
      \n
      resp := pdpb.Timestamp{}\r\nfor i := 0; i < maxRetryCount; i++ {\r\n    current, ok := s.ts.Load().(*atomicObject)\r\n    if !ok {\r\n        log.Errorf(\"we haven't synced timestamp ok, wait and retry, retry count %d\", i)\r\n        time.Sleep(200 * time.Millisecond)\r\n        continue\r\n    }\r\n\r\n    resp.Physical = current.physical.UnixNano() \/ int64(time.Millisecond)\r\n    resp.Logical = atomic.AddInt64(&current.logical, int64(count))\r\n    if resp.Logical >= maxLogical {\r\n        log.Errorf(\"logical part outside of max logical interval %v, please check ntp time, retry count %d\", resp, i)\r\n        time.Sleep(updateTimestampStep)\r\n        continue\r\n    }\r\n    return resp, nil\r\n}<\/code><\/pre>\n<\/div>\n
      \u56e0\u4e3a\u662f\u5728\u5185\u5b58\u91cc\u9762\u8ba1\u7b97\u7684\uff0c\u6240\u4ee5\u6027\u80fd\u5f88\u9ad8\uff0c\u6211\u4eec\u81ea\u5df1\u5185\u90e8\u6d4b\u8bd5\u6bcf\u79d2\u80fd\u5206\u914d\u767e\u4e07\u7ea7\u522b\u7684 TSO\u3002<\/li>\n
    4. \u5982\u679c client \u6bcf\u6b21\u4e8b\u52a1\u90fd\u5411 PD \u6765\u8bf7\u6c42\u4e00\u6b21 TSO\uff0c\u6bcf\u6b21 RPC \u7684\u5f00\u9500\u4e5f\u662f\u975e\u5e38\u5927\u7684\uff0c\u6240\u4ee5 client \u4f1a\u6279\u91cf\u7684\u5411 PD \u83b7\u53d6 TSO\u3002client \u4f1a\u9996\u5148\u6536\u96c6\u4e00\u6279\u4e8b\u52a1\u7684 TSO \u8bf7\u6c42\uff0c\u8b6c\u5982 n \u4e2a\uff0c\u7136\u540e\u76f4\u63a5\u5411 PD \u53d1\u9001\u547d\u4ee4\uff0c\u53c2\u6570\u5c31\u662f n\uff0cPD \u6536\u5230\u547d\u4ee4\u4e4b\u540e\uff0c\u4f1a\u751f\u6210 n \u4e2a TSO \u8fd4\u56de\u7ed9\u5ba2\u6237\u7aef\u3002<\/li>\n<\/ol>\n
      \u5fc3\u8df3<\/h2>\n
      \u5728\u6700\u5f00\u59cb\u6211\u4eec\u8bf4\u8fc7\uff0cPD \u6240\u6709\u5173\u4e8e\u96c6\u7fa4\u7684\u6570\u636e\u90fd\u662f\u7531 TiKV \u4e3b\u52a8\u5fc3\u8df3\u4e0a\u62a5\u7684\uff0cPD \u5bf9 TiKV \u7684\u8c03\u5ea6\u4e5f\u662f\u5728\u5fc3\u8df3\u7684\u65f6\u5019\u5b8c\u6210\u7684\u3002\u901a\u5e38 PD \u4f1a\u5904\u7406\u4e24\u79cd\u5fc3\u8df3\uff0c\u4e00\u4e2a\u662f TiKV \u81ea\u8eab store \u7684\u5fc3\u8df3\uff0c\u800c\u53e6\u4e00\u4e2a\u5219\u662f store \u91cc\u9762 region \u7684 leader peer \u4e0a\u62a5\u7684\u5fc3\u8df3\u3002<\/p>\n
      \u5bf9\u4e8e store \u7684\u5fc3\u8df3\uff0cPD \u5728 handleStoreHeartbeat \u51fd\u6570\u91cc\u9762\u5904\u7406\uff0c\u4e3b\u8981\u5c31\u662f\u5c06\u5fc3\u8df3\u91cc\u9762\u5f53\u524d\u7684 store \u7684\u4e00\u4e9b\u72b6\u6001\u7f13\u5b58\u5230 cache \u91cc\u9762\u3002store \u7684\u72b6\u6001\u5305\u62ec\u8be5 store \u6709\u591a\u5c11\u4e2a region\uff0c\u6709\u591a\u5c11\u4e2a region \u7684 leader peer \u5728\u8be5 store \u4e0a\u9762\u7b49\uff0c\u8fd9\u4e9b\u4fe1\u606f\u90fd\u4f1a\u7528\u4e8e\u540e\u7eed\u7684\u8c03\u5ea6\u3002<\/p>\n
      \u5bf9\u4e8e region \u7684\u5fc3\u8df3\uff0cPD \u5728 handleRegionHeartbeat \u91cc\u9762\u5904\u7406\u3002\u8fd9\u91cc\u9700\u8981\u6ce8\u610f\uff0c\u53ea\u6709 leader peer \u624d\u4f1a\u53bb\u4e0a\u62a5\u6240\u5c5e region \u7684\u4fe1\u606f\uff0cfollower peer \u662f\u4e0d\u4f1a\u4e0a\u62a5\u7684\u3002\u6536\u5230 region \u7684\u5fc3\u8df3\u4e4b\u540e\uff0c\u9996\u5148 PD \u4e5f\u4f1a\u5c06\u5176\u653e\u5165 cache \u91cc\u9762\uff0c\u5982\u679c PD \u53d1\u73b0 region \u7684 epoch \u6709\u53d8\u5316\uff0c\u5c31\u4f1a\u5c06\u8fd9\u4e2a region \u7684\u4fe1\u606f\u4e5f\u4fdd\u5b58\u5230 etcd \u91cc\u9762\u3002\u7136\u540e\uff0cPD \u4f1a\u5bf9\u8fd9\u4e2a region \u8fdb\u884c\u5177\u4f53\u7684\u8c03\u5ea6\uff0c\u8b6c\u5982\u53d1\u73b0 peer \u6570\u76ee\u4e0d\u591f\uff0c\u6dfb\u52a0\u65b0\u7684 peer\uff0c\u6216\u8005\u6709\u4e00\u4e2a peer \u5df2\u7ecf\u574f\u4e86\uff0c\u5220\u9664\u8fd9\u4e2a peer \u7b49\uff0c\u8be6\u7ec6\u7684\u8c03\u5ea6\u5b9e\u73b0\uff0c\u6211\u4eec\u4f1a\u5728\u540e\u7eed\u8ba8\u8bba\u3002<\/p>\n
      \u8fd9\u91cc\u518d\u8bf4\u4e00\u4e0b region \u7684 epoch\uff0c\u5728 region \u7684 epoch \u91cc\u9762\uff0c\u6709 conf_ver \u548c version\uff0c\u5206\u522b\u8868\u793a\u8fd9\u4e2a region \u4e0d\u540c\u7684\u7248\u672c\u72b6\u6001\u3002\u5982\u679c\u4e00\u4e2a region \u53d1\u751f\u4e86 membership changes\uff0c\u4e5f\u5c31\u662f\u65b0\u589e\u6216\u8005\u5220\u9664\u4e86 peer\uff0cconf_ver \u4f1a\u52a0 1\uff0c\u5982\u679c region \u53d1\u751f\u4e86 split \u6216\u8005 merge\uff0c\u5219 version \u52a0 1\u3002<\/p>\n
      \u65e0\u8bba\u662f PD \u8fd8\u662f\u5728 TiKV\uff0c\u6211\u4eec\u90fd\u662f\u901a\u8fc7 epoch \u6765\u5224\u65ad region \u662f\u5426\u53d1\u751f\u4e86\u53d8\u5316\uff0c\u4ece\u800c\u62d2\u7edd\u6389\u4e00\u4e9b\u5371\u9669\u7684\u64cd\u4f5c\u3002\u8b6c\u5982 region \u5df2\u7ecf\u53d1\u751f\u4e86\u5206\u88c2\uff0cversion \u53d8\u6210\u4e86 2\uff0c\u90a3\u4e48\u5982\u679c\u8fd9\u65f6\u5019\u6709\u4e00\u4e2a\u5199\u8bf7\u6c42\u5e26\u4e0a\u7684 version \u662f 1\uff0c \u6211\u4eec\u5c31\u4f1a\u8ba4\u4e3a\u8fd9\u4e2a\u8bf7\u6c42\u662f stale\uff0c\u4f1a\u76f4\u63a5\u62d2\u7edd\u6389\u3002\u56e0\u4e3a version \u53d8\u5316\u8868\u660e region \u7684\u8303\u56f4\u5df2\u7ecf\u53d1\u751f\u4e86\u53d8\u5316\uff0c\u5f88\u6709\u53ef\u80fd\u8fd9\u4e2a stale \u7684\u8bf7\u6c42\u9700\u8981\u64cd\u4f5c\u7684 key \u662f\u5728\u4e4b\u524d\u7684 region range \u91cc\u9762\u800c\u6ca1\u5728\u65b0\u7684 range \u91cc\u9762\u3002<\/p>\n
      Split \/ Merge<\/h2>\n
      \u524d\u9762\u6211\u4eec\u8bf4\u4e86\uff0cPD \u4f1a\u5728 region \u7684 heartbeat \u91cc\u9762\u5bf9 region \u8fdb\u884c\u8c03\u5ea6\uff0c\u7136\u540e\u76f4\u63a5\u5728 heartbeat \u7684\u8fd4\u56de\u503c\u91cc\u9762\u5e26\u4e0a\u76f8\u5173\u7684\u8c03\u5ea6\u4fe1\u606f\uff0c\u8ba9 TiKV \u81ea\u5df1\u53bb\u5904\u7406\uff0cTiKV \u5904\u7406\u5b8c\u6210\u4e4b\u540e\uff0c\u901a\u8fc7\u4e0b\u4e00\u4e2a heartbeat \u91cd\u65b0\u4e0a\u62a5\uff0cPD \u5c31\u80fd\u77e5\u9053\u662f\u5426\u8c03\u5ea6\u6210\u529f\u4e86\u3002<\/p>\n
      \u5bf9\u4e8e membership changes\uff0c\u6bd4\u8f83\u5bb9\u6613\uff0c\u56e0\u4e3a\u6211\u4eec\u6709\u6700\u5927\u526f\u672c\u6570\u7684\u914d\u7f6e\uff0c\u5047\u8bbe\u4e09\u4e2a\uff0c\u90a3\u4e48\u5f53 region \u7684\u5fc3\u8df3\u4e0a\u6765\uff0c\u53d1\u73b0\u53ea\u6709\u4e24\u4e2a peer\uff0c\u90a3\u4e48\u5c31 add peer\uff0c\u5982\u679c\u6709\u56db\u4e2a peer\uff0c\u5c31 remove peer\u3002\u800c\u5bf9\u4e8e region \u7684 split \/ merge\uff0c\u5219\u60c5\u51b5\u7a0d\u5fae\u8981\u590d\u6742\u4e00\u70b9\uff0c\u4f46\u4e5f\u6bd4\u8f83\u7b80\u5355\u3002\u6ce8\u610f\uff0c\u73b0\u9636\u6bb5\uff0c\u6211\u4eec\u53ea\u652f\u6301 split\uff0cmerge \u5904\u4e8e\u5f00\u53d1\u9636\u6bb5\uff0c\u6ca1\u5bf9\u5916\u53d1\u5e03\uff0c\u6240\u4ee5\u8fd9\u91cc\u4ec5\u4ec5\u4ee5 split \u4e3e\u4f8b\uff1a<\/p>\n
        \n
      1. \u5728 TiKV \u91cc\u9762\uff0cleader peer \u4f1a\u5b9a\u671f\u68c0\u67e5 region \u6240\u5360\u7528\u7684\u7a7a\u95f4\u662f\u5426\u8d85\u8fc7\u67d0\u4e00\u4e2a\u9600\u503c\uff0c\u5047\u8bbe\u6211\u4eec\u8bbe\u7f6e region \u7684 size \u4e3a 64MB\uff0c\u5982\u679c\u4e00\u4e2a region \u8d85\u8fc7\u4e86 96MB\uff0c \u5c31\u9700\u8981\u5206\u88c2\u3002<\/li>\n
      2. Leader peer \u4f1a\u9996\u5148\u5411 PD \u53d1\u9001\u4e00\u4e2a\u8bf7\u6c42\u5206\u88c2\u7684\u547d\u4ee4\uff0cPD \u5728 handleAskSplit \u91cc\u9762\u5904\u7406\uff0c\u56e0\u4e3a\u6211\u4eec\u662f\u4e00\u4e2a region \u5206\u88c2\u6210\u4e24\u4e2a\uff0c\u5bf9\u4e8e\u8fd9\u4e24\u4e2a\u65b0\u5206\u88c2\u7684 region\uff0c\u4e00\u4e2a\u4f1a\u7ee7\u627f\u4e4b\u524d region \u7684\u6240\u6709\u7684\u5143\u4fe1\u606f\uff0c\u800c\u53e6\u4e00\u4e2a\u76f8\u5173\u7684\u4fe1\u606f\uff0c\u8b6c\u5982 region ID\uff0c\u65b0\u7684 peer ID\uff0c\u5219\u9700\u8981 PD \u751f\u6210\uff0c\u5e76\u5c06\u5176\u8fd4\u56de\u7ed9 leader\u3002<\/li>\n
      3. Leader peer \u5199\u5165\u4e00\u4e2a split raft log\uff0c\u5728 apply \u7684\u65f6\u5019\u6267\u884c\uff0c\u8fd9\u6837 region \u5c31\u5206\u88c2\u6210\u4e86\u4e24\u4e2a\u3002<\/li>\n
      4. \u5206\u88c2\u6210\u529f\u4e4b\u540e\uff0cTiKV \u544a\u8bc9 PD\uff0cPD \u5c31\u5728 handleReportSplit \u91cc\u9762\u5904\u7406\uff0c\u66f4\u65b0 cache \u76f8\u5173\u7684\u4fe1\u606f\uff0c\u5e76\u6301\u4e45\u5316\u5230 etcd\u3002<\/li>\n<\/ol>\n
        \u8def\u7531<\/h2>\n
        \u56e0\u4e3a PD \u4fdd\u5b58\u4e86\u6240\u6709 TiKV \u7684\u96c6\u7fa4\u4fe1\u606f\uff0c\u81ea\u7136\u5bf9 client \u63d0\u4f9b\u4e86\u8def\u7531\u7684\u529f\u80fd\u3002\u5047\u8bbe client \u8981\u5bf9 key \u5199\u5165\u4e00\u4e2a\u503c\u3002<\/p>\n
          \n
        1. client \u5148\u4ece PD \u83b7\u53d6 key \u5c5e\u4e8e\u54ea\u4e00\u4e2a region\uff0cPD \u5c06\u8fd9\u4e2a region \u76f8\u5173\u7684\u5143\u4fe1\u606f\u8fd4\u56de\u3002<\/li>\n
        2. client \u81ea\u5df1 cache\uff0c\u8fd9\u6837\u5c31\u4e0d\u9700\u8981\u6bcf\u6b21\u90fd\u4ece PD \u83b7\u53d6\u3002\u7136\u540e\u76f4\u63a5\u7ed9 region \u7684 leader peer \u53d1\u9001\u547d\u4ee4\u3002<\/li>\n
        3. \u6709\u53ef\u80fd region \u7684 leader \u5df2\u7ecf\u6f02\u79fb\u5230\u5176\u4ed6 peer\uff0cTiKV \u4f1a\u8fd4\u56de NotLeader \u9519\u8bef\uff0c\u5e76\u5e26\u4e0a\u65b0\u7684 leader \u7684\u5730\u5740\uff0cclient \u5728 cache \u91cc\u9762\u66f4\u65b0\uff0c\u5e76\u91cd\u65b0\u5411\u65b0\u7684 leader \u53d1\u9001\u8bf7\u6c42\u3002<\/li>\n
        4. \u4e5f\u6709\u53ef\u80fd region \u7684 version \u5df2\u7ecf\u53d8\u5316\uff0c\u8b6c\u5982 split \u4e86\uff0c\u8fd9\u65f6\u5019\uff0ckey \u53ef\u80fd\u5df2\u7ecf\u843d\u5165\u4e86\u65b0\u7684 region \u4e0a\u9762\uff0cclient \u4f1a\u6536\u5230 StaleCommand \u7684\u9519\u8bef\uff0c\u4e8e\u662f\u91cd\u65b0\u4ece PD \u83b7\u53d6\uff0c\u8fdb\u5165\u72b6\u6001 1\u3002<\/li>\n<\/ol>\n
          \u5c0f\u7ed3<\/h2>\n
          PD \u4f5c\u4e3a TiDB \u96c6\u7fa4\u7684\u4e2d\u5fc3\u8c03\u5ea6\u6a21\u5757\uff0c\u5728\u8bbe\u8ba1\u4e0a\u9762\uff0c\u6211\u4eec\u5c3d\u91cf\u4fdd\u8bc1\u65e0\u72b6\u6001\uff0c\u65b9\u4fbf\u6269\u5c55\u3002\u672c\u7bc7\u6587\u7ae0\u4e3b\u8981\u4ecb\u7ecd\u4e86 PD \u662f\u5982\u4f55\u8ddf TiKV\uff0cTiDB \u534f\u4f5c\u4ea4\u4e92\u7684\u3002\u540e\u9762\uff0c\u6211\u4eec\u4f1a\u8be6\u7ec6\u5730\u4ecb\u7ecd\u6838\u5fc3\u8c03\u5ea6\u529f\u80fd\uff0c\u4e5f\u5c31\u662f PD \u662f\u5982\u4f55\u63a7\u5236\u6574\u4e2a\u96c6\u7fa4\u7684\u3002<\/p>\n<\/div>\n<\/div>\n
          \u7f16\u8f91\u4e8e 2017-01-10<\/div>\n","protected":false},"excerpt":{"rendered":"
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