{"id":224755,"date":"2014-08-05T19:07:52","date_gmt":"2014-08-05T11:07:52","guid":{"rendered":"http:\/\/yangzhe1991.org\/blog\/?p=224755"},"modified":"2015-04-16T17:49:06","modified_gmt":"2015-04-16T09:49:06","slug":"lightweight-transactions-in-cassandra","status":"publish","type":"post","link":"https:\/\/yangzhe1991.org\/blog\/2014\/08\/lightweight-transactions-in-cassandra\/","title":{"rendered":"Cassandra\u6e90\u7801\u9605\u8bfb\u4e4b\u8f7b\u91cf\u7ea7\u4e8b\u52a1(compare-and-set, CAS)\u7684\u5b9e\u73b0"},"content":{"rendered":"<p>\u6700\u8fd1\u65f6\u95f4\u6bd4\u8f83\u5145\u88d5\uff0c\u4f5c\u4e3a\u4e00\u4e2a\u7528\u6237\u5bf9Cassandra\u7684\u8ba4\u8bc6\u4e5f\u7b97\u9010\u6e10\u6df1\u5165\uff0c\u56e0\u6b64\u5f00\u59cb\u7cfb\u7edf\u6027\u5730\u6765\u9605\u8bfb\u6e90\u7801\u3002\u770b\u660e\u767d\u67d0\u4e2a\u5730\u65b9\u4e4b\u540e\u5c31\u968f\u624b\u5199\u4e2a\u535a\u5ba2\u5565\u7684\uff0c\u5e2e\u81ea\u5df1\u6574\u7406\u601d\u8def\uff0c\u987a\u4fbf\u4e89\u53d6\u8ba9\u770b\u5230\u7684\u4eba\u6709\u6240\u6536\u83b7\u3002<\/p>\n<p><!--more--><\/p>\n<p>\u4e4b\u524d\u63d0\u5230\u8fc7\u4ffa\u4eec\u516c\u53f8\u653e\u5f03\u4e86\u81ea\u5df1\u9020\u7684\u5206\u5e03\u5f0f\u6570\u636e\u5e93\u8f6e\u5b50\uff0c<a href=\"https:\/\/yangzhe1991.org\/blog\/2014\/05\/cassandra\/\">\u5f00\u59cb\u7528Cassandra<\/a>\uff0c\u51e0\u4e2a\u6708\u4ee5\u6765\u867d\u7136\u6709\u5404\u79cd\u5c0f\u5751\uff0c\u4f46\u5927\u5751\u6682\u65f6\u6ca1\u9047\u5230\u3002\u800c\u4e14\u5c0f\u5751\u6709\u8d85\u8fc7\u4e00\u534a\u662f\u56e0\u4e3a\u6211\u4eec\u662f\u4ece\u73b0\u6709\u673a\u5668\u91cc\u627e\u4e86\u4e00\u6279\u5373\u5c06\u4e0b\u7ebf\u7684\u6027\u80fd\u6700\u632b\u7684\u6ca1\u4eba\u8981\u7684\u673a\u5668\u6765\u642d\uff0c\u78c1\u76d8\u4e5f\u4e0d\u591f\u5927\uff0c\u5bfc\u81f4load\u592a\u9ad8\u3001\u78c1\u76d8\u6027\u80fd\u53d8\u5dee\u6216\u8005\u78c1\u76d8\u6ee1\u4e86\u4ece\u800c\u5f71\u54cd\u7ebf\u4e0a\u670d\u52a1\u3002\u76ee\u524d\u8bcd\u5178\u7684\u5355\u8bcd\u771f\u4eba\u53d1\u97f3\u6216\u4f8b\u53e5tts\u53d1\u97f3\u3001\u5355\u8bcd\u672c\uff0c\u8fd8\u6709\u6709\u9053\u516c\u7528\u7684\u56fe\u7247\u670d\u52a1\u7684\u5e95\u5c42\u6570\u636e\u90fd\u5728Cassandra\u4e0a\uff0c\u603b\u4f53\u8bf4\u6765\u8fd8\u662f\u633a\u9760\u8c31\u7684\u3002\u4e92\u8054\u7f51\u76f8\u5173\u7684\u6280\u672f\u53d1\u5c55\u901f\u5ea6\u592a\u731b\uff0c\u4e00\u4e24\u5e74\u4e00\u4e2a\u5927\u53d8\u6837\uff0c\u4e0d\u6bd4\u6469\u5c14\u5b9a\u5f8b\u6162\uff0cCassandra\u521d\u671f\u4e0d\u9760\u8c31\u7136\u540e\u5bfc\u81f42010\u5e74\u5de6\u53f3\u8fdeFB\u81ea\u5df1\u90fd\u653e\u5f03\u4e86\u4e4b\u540e\u7559\u4e0b\u592a\u591a\u9ed1\u5b83\u7684\u8a00\u8bba\uff0c\u4e8e\u662f\u5bfc\u81f4\u57282013\u30012014\u5e74\u5f88\u591a\u4eba\u63d0\u5230Cassandra\u8fd8\u662f\u770b\u5230\u4e86\u5386\u53f2\u65f6\u671f\u5c24\u5176\u662f1.0\u4e4b\u524d\u65f6\u671f\u7684\u5410\u69fd\u6700\u7ec8\u653e\u5f03\u8c03\u7814Cassandra\uff0c\u8fd8\u662f\u633a\u9057\u61be\u7684\u3002\u5c24\u5176\u662f\u5176\u5b9e2013\u5e74\u5f00\u59cb<a href=\"http:\/\/planetcassandra.org\/blog\/post\/cassandra-comes-home-facebooks-parse-choses-cassandra-for-mobile-app-development-platform\/\">FB\u81ea\u5df1\u4e5f\u91cd\u65b0\u5728\u67d0\u4e9b\u9879\u76ee\u7528Cassandra\u4e86<\/a>\uff0c\u4e0d\u8fc7\u8c01\u8ba9Cassandra\u7684\u8d44\u6599\u6bd4hbase\u5c11\u592a\u591a\u5462\uff0c\u5c24\u5176\u662f\u8fde\u5b98\u65b9wiki\u90fd\u5f31\u7206\u4e86\uff0c\u5b8c\u5168\u662f\u9760Datastax\u90a3\u4e2a\u5546\u4e1a\u516c\u53f8\u5199\u7248\u6743\u5c5e\u4e8e\u4ed6\u4eec\u516c\u53f8\u7684\u6587\u6863\u3002\u5f53\u7136\u90a3\u4e2a\u6587\u6863\u53ea\u80fd\u4f5c\u4e3a\u7528\u6237\u770b\uff0c\u5927\u591a\u6570\u65f6\u5019\u6ca1\u592a\u8bf4\u5e95\u5c42\u7684\u5b9e\u73b0\uff0c\u597d\u5947\u5fc3\u592a\u91cd\u7684\u8bdd\uff0c\u8fd8\u662f\u8981\u770b\u4ee3\u7801\u3002<\/p>\n<p>\u8a00\u5f52\u6b63\u4f20\uff0cC*\uff08\u6309\u793e\u533a\u60ef\u4f8b\uff0cCassandra\u7b80\u5199\u4e3aC*\uff09\u56e0\u4e3a\u53bb\u6389\u4e86\u4e2d\u5fc3\u8282\u70b9master\uff0c\u4e5f\u4e0d\u7528\u5206\u5e03\u5f0f\u7684\u7ba1\u7406\u7ec4\u4ef6zookeeper\uff0c\u5b8c\u5168\u662f\u9760W+R&gt;N\u6765\u5b9e\u73b0\u6570\u636e\u8bfb\u5199\u7684\u4e00\u81f4\u6027\uff0c\u80fd\u4fdd\u8bc1\u8bfb\u5230\u7684\u4e00\u5b9a\u662f\u201c\u65f6\u95f4\u6233\u6700\u5927\u201d\u4e00\u6b21\u5199\u8fc7\u7684\u3002\u4f46\u5982\u679c\u4fe9\u7ebf\u7a0b\u540c\u65f6\u5199\uff0c\u4f1a\u5bfc\u81f4\u4e00\u524d\u4e00\u540e\u5199\u8fdb\u53bb\uff0c\u4e24\u4e2aclient\u7ebf\u7a0b\u90fd\u8ba4\u4e3a\u81ea\u5df1\u5199\u6210\u529f\u4e86\uff0c\u4f46\u5b9e\u9645\u4e0a\u540e\u5199\u7684\u8986\u76d6\u4e86\u65b0\u5199\u7684\uff0c\u4e5f\u5c31\u662fACID\u91cc\u7684I\uff0c\u9694\u79bb\u6027\uff0c\u6ca1\u4fdd\u969c\u3002\u4e3e\u4f8b\u5c31\u662f\uff0c\u4fe9\u7528\u6237\u540c\u65f6\u62a2\u6ce8\u4e00\u4e2aid\uff0c\u4e1a\u52a1\u903b\u8f91\u4f1a\u56e0\u4e3a\u90fd\u5199\u6210\u529f\u4e86\u800c\u8ba4\u4e3a\u4fe9\u4eba\u90fd\u6ce8\u518c\u6210\u529f\u4e86\uff0c\u4f46\u5b9e\u9645\u4e0a\u662f\u51b2\u7a81\u4e86\u3002<\/p>\n<p>\u6240\u4ee5C*\u4ece2.0\u5f00\u59cb\u57fa\u4e8ePaxos\u7b97\u6cd5\u652f\u6301\u8f7b\u91cf\u7ea7\u5355row key\u4e8b\u52a1\uff0c\u6765\u786e\u4fdd\u9694\u79bb\u6027\u3002\u652f\u6301\u7684\u64cd\u4f5c\u4e3b\u8981\u662finsert &#8230; if not exist; delete &#8230; if exist; update &#8230; if col=value\u4e09\u79cd\uff0c\u53e6\u5916\u4e0d\u5e38\u7528\u7684\u53ef\u80fd\u5c31\u662fcreate table if not exist\u548cdrop table if exist\u3002\u5176\u4e00\u81f4\u6027\u4e5f\u4e0d\u518d\u662f\u5bf9\u6570\u91cf\u7684\u8981\u6c42\u800c\u662flinearizable\u6216\u8005\u672c\u5730\u673a\u623f\u5185linearizable\u5373local_linearizable\u3002\u5f53\u7136\uff0c\u57fa\u4e8einsert if not exist\u4ee5\u53cattl\u5b8c\u5168\u53ef\u4ee5\u5b9e\u73b0\u4e00\u4e2a\u7b80\u6613\u7684\u5206\u5e03\u5f0f\u9501\uff0c\u6267\u884c\u66f4\u590d\u6742\u7684\u903b\u8f91\u3002\u62ff\u5230\u63d2\u5165\u6743\u5c31\u662f\u62ff\u5230\u4e86\u9501\uff0c\u62ff\u4e0d\u5230\u5c31\u77ed\u6682sleep\u540e\u518d\u5c1d\u8bd5\u3002ttl\u662f\u4e3a\u4e86\u8ba9\u8fd9\u884c\u6570\u636e\u5728\u4e00\u6bb5\u65f6\u95f4\u540e\u81ea\u52a8\u5220\u9664\uff0c\u9632\u6b62\u62ff\u5230\u9501\u4e4b\u540e\u7a0b\u5e8f\u6302\u6389\u6ca1\u5220\u9664\u5bfc\u81f4\u6b7b\u9501\u3002<\/p>\n<p>\u4ecb\u7ecd\u5177\u4f53\u5b9e\u73b0\u524d\u5148\u7b80\u5355\u4ecb\u7ecd\u4e0bC*\u7684\u67b6\u6784\u3002\u5b83\u662f\u5178\u578b\u7684SEDA(<span style=\"color: #333333;\">Staged Event-Driven Architecture<\/span>)\u67b6\u6784\uff0c\u5373\u628a\u4e00\u4e2a\u5b8c\u6574\u884c\u4e3a\u62c6\u5206\u6210\u82e5\u5e72\u4e2a\u9636\u6bb5(Stage)\uff0c\u9636\u6bb5\u4e4b\u95f4\u7528\u6d88\u606f\u548c\u56de\u8c03\u8fdb\u884c\u5f02\u6b65\u4ea4\u4e92\u3002\u56e0\u4e3a\u4e00\u4e2a\u5b8c\u6574\u7684\u64cd\u4f5c\u6d41\u7a0b\u5728\u4e0d\u540c\u9636\u6bb5\u5bf9\u8d44\u6e90\u7684\u5360\u7528\u662f\u4e0d\u540c\u7684\uff0c\u8fd9\u4e2a\u67b6\u6784\u53ef\u4ee5\u6bd4\u8f83\u65b9\u4fbf\u7684\u5728\u4e0d\u540c\u9636\u6bb5\u5f00\u4e0d\u540c\u5927\u5c0f\u7684\u7ebf\u7a0b\u6c60\u4ece\u800c\u6700\u5927\u5316\u5168\u5c40\u7684\u6027\u80fd\uff0c\u540c\u65f6\u56e0\u4e3a\u6709\u4e00\u4e2a\u6d88\u606f\u4f20\u9012\u7684\u4e2d\u8f6c\u961f\u5217\uff0c\u4e00\u5b9a\u7a0b\u5ea6\u4e0a\u4e5f\u7b97\u89e3\u8026\u5408\uff0c\u53ea\u9700\u8981\u6839\u636e\u4e2d\u8f6c\u961f\u5217\u7684\u63a5\u53e3\u5b9e\u73b0\u4e00\u4e2a\u4e2a\u9636\u6bb5\u7684handler\u5373\u53ef\u3002C*\u91cc\u6709\u4e2a\u4e13\u95e8\u7684MessagingService\u8d1f\u8d23\u6536\u53d1\u6d88\u606f\uff0c\u6bcf\u4e2a\u6d88\u606f\u6709\u4e2a\u5bf9\u5e94\u7684Verb\u679a\u4e3e\u7c7b\u6765\u8bf4\u660e\u8fd9\u4e2a\u6d88\u606f\u662f\u4ec0\u4e48\u7c7b\u578b\u7684\uff0c\u7528\u4e00\u4e2amap\u6765\u6ce8\u518c\u6536\u5230\u67d0\u4e2a\u6d88\u606f\u540e\u8be5\u88ab\u54ea\u4e2aHandler\u63a5\u6536\u3002\u53d1\u6d88\u606f\u53ef\u80fd\u53d1\u7ed9\u672c\u5730\u4e5f\u53ef\u80fd\u53d1\u7ed9\u5176\u4ed6\u8282\u70b9\u3002<\/p>\n<p>\u8df3\u8fc7\u4ece\u67d0\u4e2a\u8282\u70b9\u63a5\u5230client\u8bf7\u6c42\u5230\u5904\u7406\u5b8cCQL\u8bed\u53e5\u7b49\u90e8\u5206\uff0c\u5f53\u53d1\u73b0query\u4e2d\u5305\u62ec\u4e86&#8221;if&#8221;\u8fd9\u79cd\u6709\u6761\u4ef6\u7684\u884c\u4e3a\u5373\u8f7b\u91cf\u7ea7\u4e8b\u52a1\u4e4b\u540e\uff0c\u6267\u884cStorageProxy.cas\u65b9\u6cd5\u3002StorageProxy\u53ef\u4ee5\u7406\u89e3\u4e3a\u5bf9\u4efb\u4f55\u67e5\u8be2\u7684\u5904\u7406\uff0c\u518d\u6b64\u4e4b\u524d\u7684\u4e1c\u897f\uff08\u4e3b\u8981\u662f\u5904\u7406CQL\u6216\u8005\u65e7\u7248\u7684thrift\u8bf7\u6c42\uff09\u597d\u50cf\u90fd\u4e0d\u662f\u5f02\u6b65\u7684\u3002cas\u65b9\u6cd5\u4e2d\u5148\u901a\u8fc7row key\u83b7\u53d6token\uff0c\u6839\u636etoken\u7b97\u54ea\u51e0\u4e2a\u8282\u70b9\u5b58\u4e86\u8fd9\u4efd\u6570\u636e\u3002\u7136\u540e\u5f00\u59cb\u8fdb\u884cPaxos\u7b97\u6cd5\u7684prepare\u9636\u6bb5\u2014\u2014\u8fd9\u4e2a\u9636\u6bb5\u548cC*\u81ea\u5df1\u7684SEDA\u7684\u9636\u6bb5\u4e24\u7801\u4e8b\u3002<\/p>\n<p>\u5c06Prepare\u6d88\u606f\u53d1\u5230\u6240\u6709\u4fdd\u5b58\u8be5row key\u7684\u8282\u70b9\uff0c\u5bf9\u5e94\u8282\u70b9\u7684MessagingService\u6536\u5230\u4e86MessagingService.Verb.PAXOS_PREPARE\u8fd9\u4e2a\u7c7b\u578b\u7684\u6d88\u606f\u540e\u7531\u5bf9\u5e94\u6ce8\u518c\u7684PrepareVerbHandler\u6765\u5904\u7406\u3002Paxos\u7684prepare\u9636\u6bb5\u5f88\u7b80\u5355\uff0c\u6536\u5230prepare\u7684\u6d88\u606f\u540e\u8ddf\u672c\u5730\u5df2\u7ecf\u6536\u5230\u7684\u6700\u5927\u7248\u672c\u53f7(C*\u91cc\u7528timeUUID\u6765\u4f5c\u4e3a\u7248\u672c\u53f7)\u6bd4\u8f83\uff0c\u6bd4\u4e4b\u524d\u7684\u5927\u5219\u63a5\u53d7\uff0c\u5426\u5219\u62d2\u7edd\u5e76\u8ba9\u53d1\u8d77\u8005\u7ec8\u6b62\u672c\u6b21\u8bf7\u6c42\u3002<\/p>\n<p>\u5177\u4f53\u5b9e\u73b0\u662f\u5728PaxosState.prepare\u65b9\u6cd5\uff0c\u56e0\u4e3aprepare\u7684\u72b6\u6001\u66f4\u65b0\u8981\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\uff0c\u91cc\u9762\u641e\u4e861024\u4e2a\u9501\uff0c\u5148\u628akey\u54c8\u5e0c\u57280-1023\u4e4b\u95f4\u7136\u540e\u7528synchronized\u540c\u6b65\u3002\u8fdb\u4e86\u540c\u6b65\u5757\u4e4b\u540e\uff0c\u5148\u4ecesystem.paxos\u8868\u62ffquery\u5bf9\u5e94\u8868\u5bf9\u5e94\u884c\u7684\u72b6\u6001\u3002system\u8fd9\u4e2akeyspace\u662f\u4e13\u95e8\u5b58\u5404\u79cd\u7cfb\u7edf\u4fe1\u606f\u7684\uff0c\u8bfb\u5199\u5e94\u8be5\u90fd\u4e0d\u4f1a\u548c\u5176\u4ed6\u8282\u70b9\u8fdb\u884c\u540c\u6b65\uff0c\u5404\u641e\u5404\u7684\uff08\u4e8e\u662f\u5982\u679cdata\u5b58\u5728\u591a\u4e2a\u78c1\u76d8\u7136\u540e\u5176\u4e2d\u4e00\u4e2a\u78c1\u76d8\u6302\u4e86\u5c31\u53ef\u80fd\u4f1a\u5bfc\u81f4system\u6570\u636e\u635f\u574f\u7136\u540e\u5f00\u59cb\u5404\u79cd\u83ab\u540d\u5176\u5999\uff0c\u6240\u4ee5\u6211\u73b0\u5728\u5982\u679c\u6362\u4e00\u4e2a\u76d8\u4e5f\u90fd\u4f1a\u628a\u90a3\u4e2a\u8282\u70b9\u6570\u636e\u5168\u6e05\u7a7a\u91cd\u65b0nodetool rebuild\u4ece\u5176\u4ed6\u8282\u70b9\u5bfc\u6570\u636e\uff09\u3002paxos\u8fd9\u4e2a\u8868\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n<p><a href=\"https:\/\/yangzhe1991.org\/blog\/wp-content\/uploads\/2014\/08\/\u5c4f\u5e55\u5feb\u7167-2014-08-05-\u4e0b\u53486.00.52.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-224760\" src=\"https:\/\/yangzhe1991.org\/blog\/wp-content\/uploads\/2014\/08\/\u5c4f\u5e55\u5feb\u7167-2014-08-05-\u4e0b\u53486.00.52.png\" alt=\"system.paxos\" width=\"227\" height=\"162\" \/><\/a><\/p>\n<p>in_progress_ballot\u3001proposal\u3001most_recent_commit\u5206\u522b\u4ee3\u8868\u6b63\u5728\u63d0\u8bae(prepare)\u3001\u5df2\u7ecf\u63a5\u53d7\u63d0\u8bae(propose)\u548c\u6700\u8fd1\u4e00\u6b21\u63d0\u4ea4\u6210\u529f\u3002\u6ce8\u610f\u8fd9\u4e2a\u63a5\u53d7\u662f\u6309\u7167paxos\u7b97\u6cd5\u9700\u8981\u591a\u6570\u540c\u610f\u4e14\u65e0\u4eba\u5426\u51b3(\u540c\u610f\u548c\u5426\u51b3\u4e4b\u5916\u7684\u7b2c\u4e09\u79cd\u60c5\u51b5\u662f\u8d85\u65f6\u65e0\u54cd\u5e94)\u8fd9\u4e2a\u63d0\u8bae\u4e4b\u540e\u624d\u7b97\u201c\u63a5\u53d7\u201d\uff0c\u81ea\u5df1\u201c\u540c\u610f\u201d\u67d0\u4e2a\u63d0\u8bae\u4e0d\u7b97\u3002\u62ff\u5230\u8fd9\u4e2a\u4fe1\u606f\u4e4b\u540e\uff0c\u7528in_progress_ballot\u8ddf\u6536\u5230\u7684\u8fd9\u4e2a\u6d88\u606f\u7684\u65f6\u95f4\u6233\u505a\u6bd4\u8f83\uff0c\u5982\u679c\u76f8\u540c\u6216\u6536\u5230\u7684\u66f4\u5927\uff08\u5224\u65ad\u662f\u5426\u76f8\u540c\u597d\u50cf\u662f\u56e0\u4e3a\u53ef\u80fd\u4f1a\u91cd\u8bd5\uff1f\u4e0d\u7136timeuuid\u7406\u8bba\u4e0a\u5e94\u8be5\u4e0d\u4f1a\u91cd\u590d\u7684\u554a\u800cprepare\u4e5f\u4e0d\u4f1a\u7528\u540c\u4e00\u4e2a\u7248\u672c\u53f7\u91cd\u590d\u4e24\u6b21\uff0c\u96be\u9053\u6211\u7406\u89e3\u9519\u4e86\u2026\u2026\uff09\u5c31\u540c\u610f\u8fd9\u4e2a\u63d0\u8bae\u3002\u5982\u679c\u540c\u610f\u5c31\u628a\u8fd9\u4e2a\u65f6\u95f4\u6233\u66f4\u65b0\u5230system.paxos\u8868\u5bf9\u5e94\u884c\u7684in_progress_ballot\u4e2d\uff0c\u5e76\u8bbettl\u3002\u5224\u65ad\u80fd\u5426\u540c\u610f\u8fd9\u4e2a\u63d0\u8bae\u4e4b\u540e\uff0c\u8fd4\u56de\u4e2abool\u7c7b\u578b\u56de\u8c03\u7ed9\u53d1\u8d77\u63d0\u8bae\u7684leader(\u5373\u6536\u5230client\u8bf7\u6c42\u7684\u90a3\u4e2a\u8282\u70b9)\u3002\u5982\u679c\u4e3atrue\u5219\u989d\u5916\u8fd4\u56de\u6700\u8fd1\u4e00\u6b21\u63a5\u53d7\u7684\u5185\u5bb9\u4ee5\u53ca\u6700\u8fd1\u4e00\u6b21\u63d0\u4ea4\u6210\u529f\u7684\u5185\u5bb9\uff0c\u5185\u5bb9\u5305\u62ec\u5177\u4f53query\u548c\u7248\u672c\u53f7\uff0c\u5373proposal\u3001proposal_ballot\u548cmost_recent_commit\u3001most_recent_commit_at\uff1b\u5982\u679c\u4e3afalse\u989d\u5916\u8fd4\u56de\u5df2\u7ecf\u6536\u5230\u8fc7\u7684\u90a3\u4e2aprepare\u7684\u7248\u672c\u53f7\u4ee5\u53ca\u6700\u8fd1\u4e00\u6b21\u63d0\u4ea4\u6210\u529f\u7684\u5185\u5bb9\u5373in_progress_ballot\u548cmost_recent_commit\u3001most_recent_commit_at\u3002\u56de\u8c03\u4e5f\u662f\u4e00\u6b21\u6d88\u606f\u4f20\u9012\uff0c\u7531N\u4e2a\u8282\u70b9\u53d1\u9001\u7ed9\u5904\u7406client\u8bf7\u6c42\u7684\u90a3\u4e2a\u8282\u70b9\u3002<\/p>\n<p>PrepareCallback\u8d1f\u8d23\u5904\u7406\u56de\u8c03\uff0c\u4e00\u6b21prepare\u8bf7\u6c42\u53ea\u6709\u4e00\u4e2acallback\u5b9e\u4f8b\uff0c\u591a\u4e2a\u8282\u70b9\u5206\u522b\u56de\u8c03\u90fd\u4f1a\u8c03\u7528\u8fd9\u4e00\u4e2a\u5b9e\u4f8b\u3002\u5904\u7406callback\u7684\u65f6\u5019\u540c\u65f6\u8bb0\u5f55\u6240\u6709\u8fd4\u56de\u7684\u8282\u70b9\u7684inProgressCommitWithUpdate(in_progress_ballot\/proposal)\u6700\u5927\u7248\u672c\u53f7\u4ee5\u53cacommit\u6210\u529f\u7684\u6700\u5927\u7248\u672c\u53f7\uff0c\u8fd9\u4e24\u4e2a\u7248\u672c\u53f7\u540e\u9762\u4f1a\u7528\u3002\u5728\u8d85\u65f6\u65f6\u95f4\u7ed3\u675f\u524d\u5982\u679c\u6709\u591a\u6570\u8282\u70b9\u540c\u610f\u4e14\u65e0\u4eba\u62d2\u7edd\u5219\u901a\u8fc7\u6b64prepare\uff1b\u53ea\u8981\u6709\u4e00\u4e2a\u8282\u70b9\u62d2\u7edd\u63d0\u8bae\uff0c\u6574\u4e2a\u63d0\u8bae\u4f5c\u5e9f\u4e2d\u6b62\uff1b\u8d85\u65f6\u65f6\u95f4\u622a\u6b62\u524d\u6ca1\u6709\u591a\u6570\u540c\u610f\uff0c\u76f4\u63a5\u629b\u8d85\u65f6\u5f02\u5e38\uff0c\u4f3c\u4e4e\u5c31\u4e0d\u4f1a\u518d\u91cd\u8bd5\u76f4\u63a5\u62a5\u9519\u7ed9\u5ba2\u6237\u7aef\u3002<\/p>\n<p>\u5982\u679c\u88ab\u62d2\u7edd\uff0c\u628a\u5bfc\u81f4\u4e2d\u6b62\u7684\u56de\u8c03\u4f20\u6765\u7684in_progress_ballot+1\u548c\u5f53\u524d\u7cfb\u7edf\u65f6\u95f4\u6233\u53d6\u6700\u5927\u751f\u6210\u4e00\u4e2a\u65b0\u7684\u7248\u672c\u53f7\u518d\u5c1d\u8bd5prepare\uff0c\u4e4b\u6240\u4ee5\u8981\u4e24\u8005\u6700\u5927\u662f\u56e0\u4e3a\u6bcf\u4e2a\u8282\u70b9\u7684\u65f6\u949f\u53ef\u80fd\u6709\u504f\u5dee\uff0c\u8981\u4fdd\u8bc1\u5168\u5c40\u603b\u662f\u66f4\u5927\u7684\u3002\u5904\u7406\u6bcf\u4e2a\u56de\u8c03\u7684\u8bf7\u6c42\u7684\u540c\u65f6\uff0c\u5206\u522b\u4fdd\u5b58\u6240\u6709\u56de\u8c03\u4e2dproposal_ballot\u548cmost_recent_commit_at\u7684\u4e24\u4e2a\u6700\u5927\u503c(\u5c31\u662f\u4e0a\u4e00\u6bb5\u63d0\u5230\u7684\u4e24\u4e2a\u7248\u672c\u53f7)\u3002\u5982\u679c\u53d1\u73b0\u6709\u524d\u8005\u6bd4\u540e\u8005\u5927\uff0c\u8bf4\u660e\u76ee\u524d\u7cfb\u7edf\u7684\u72b6\u6001(\u6570\u636e)\u5e76\u4e0d\u662f\u6700\u65b0\uff0c\u5373\u4f7f\u5bf9\u5e94\u8282\u70b9\u63a5\u53d7\u4e86\u672c\u6b21prepare\u4e5f\u9700\u8981\u5148\u5b8c\u6210\u524d\u4e00\u6b21commit\u3002\u6240\u4ee5\u4f1a\u5148\u7528\u81ea\u5df1\u751f\u6210\u7684\u8fd9\u4e2a\u7248\u672c\u53f7\u63a8\u8fdb\u4ed6\u5b8c\u6210(\u7528\u8fd9\u4e2a\u7248\u672c\u53f7\u6267\u884c\u540e\u7eedpropose\u3001commit\u9636\u6bb5)\u3002\u8fd9\u6837\u624d\u80fd\u4fdd\u8bc1\u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href=\"https:\/\/yangzhe1991.org\/blog\/wp-content\/uploads\/2014\/08\/paxos-3-full-cas.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-224761\" src=\"https:\/\/yangzhe1991.org\/blog\/wp-content\/uploads\/2014\/08\/paxos-3-full-cas.png\" alt=\"paxos-3-full-cas\" width=\"411\" height=\"761\" srcset=\"https:\/\/yangzhe1991.org\/blog\/wp-content\/uploads\/2014\/08\/paxos-3-full-cas.png 411w, https:\/\/yangzhe1991.org\/blog\/wp-content\/uploads\/2014\/08\/paxos-3-full-cas-162x300.png 162w\" sizes=\"(max-width: 411px) 100vw, 411px\" 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