Zookeeper 源码分析-启动

Zookeeper 源码分析-启动

博客分类：

 
• Zookeeper

 

   本文主要介绍了zookeeper启动的过程

   运行zkServer.sh start命令可以启动zookeeper。入口的main函数在类中QuorumPeerMain。

   main函数主要调用了runFromConfig函数，创建了QuorumPeer对象，并且调用了start函数，从而启动了zookeeper。

public class QuorumPeerMain {
     protected QuorumPeer quorumPeer;

    /**
     * To start the replicated server specify the configuration file name on
     * the command line.
     * @param args path to the configfile
     */
    public static void main(String[] args) {
        QuorumPeerMain main = new QuorumPeerMain();
        main.initializeAndRun(args);
    }

    protected void initializeAndRun(String[] args)
        throws ConfigException, IOException
    {
        runFromConfig(config);
    }

    public void runFromConfig(QuorumPeerConfig config) throws IOException {
      LOG.info("Starting quorum peer");
      try {
          NIOServerCnxn.Factory cnxnFactory =
              new NIOServerCnxn.Factory(config.getClientPortAddress(),
                      config.getMaxClientCnxns());

          quorumPeer = new QuorumPeer();
          quorumPeer.setClientPortAddress(config.getClientPortAddress());
          quorumPeer.setTxnFactory(new FileTxnSnapLog(
                      new File(config.getDataLogDir()),
                      new File(config.getDataDir())));
          quorumPeer.setQuorumPeers(config.getServers());
          quorumPeer.setElectionType(config.getElectionAlg());
          quorumPeer.setMyid(config.getServerId());
          quorumPeer.setTickTime(config.getTickTime());
          quorumPeer.setMinSessionTimeout(config.getMinSessionTimeout());
          quorumPeer.setMaxSessionTimeout(config.getMaxSessionTimeout());
          quorumPeer.setInitLimit(config.getInitLimit());
          quorumPeer.setSyncLimit(config.getSyncLimit());
          quorumPeer.setQuorumVerifier(config.getQuorumVerifier());
          quorumPeer.setCnxnFactory(cnxnFactory);
          quorumPeer.setZKDatabase(new ZKDatabase(quorumPeer.getTxnFactory()));
          quorumPeer.setLearnerType(config.getPeerType());

          quorumPeer.start();
          quorumPeer.join();
      } catch (InterruptedException e) {
          // warn, but generally this is ok
          LOG.warn("Quorum Peer interrupted", e);
      }
    }
}

    在QuorumPeer的start函数中，先调用了loadDataBase方法用于恢复数据。启动与client交互的线程，并

@Override
public synchronized void start() {
    try {
        zkDb.loadDataBase();
    } catch(IOException ie) {
        LOG.fatal("Unable to load database on disk", ie);
        throw new RuntimeException("Unable to run quorum server ", ie);
    }
    cnxnFactory.start(); //用于处理与client的交互
    startLeaderElection();//开始选举算法
    super.start();
}

    调用loadDatabase从磁盘加载数据到内存

public long loadDataBase() throws IOException {
    PlayBackListener listener=new PlayBackListener(){
        public void onTxnLoaded(TxnHeader hdr,Record txn){
            Request r = new Request(null, 0, hdr.getCxid(),hdr.getType(),
                    null, null);
            r.txn = txn;
            r.hdr = hdr;
            r.zxid = hdr.getZxid();
            addCommittedProposal(r);
        }
    };

    long zxid = snapLog.restore(dataTree,sessionsWithTimeouts,listener);
    initialized = true;
    return zxid;
}

    调用QuorumPeer的run函数，按照peer的state做不同的处理

@Override
   public void run() {
       setName("QuorumPeer:" + cnxnFactory.getLocalAddress());

       try {
           /*
            * Main loop
            */
           while (running) {
               switch (getPeerState()) {
               case LOOKING:
                   try {
                       LOG.info("LOOKING");
                       setCurrentVote(makeLEStrategy().lookForLeader());
                   } catch (Exception e) {
                       LOG.warn("Unexpected exception",e);
                       setPeerState(ServerState.LOOKING);
                   }
                   break;
               case OBSERVING:
                   try {
                       LOG.info("OBSERVING");
                       setObserver(makeObserver(logFactory));
                       observer.observeLeader();
                   } catch (Exception e) {
                       LOG.warn("Unexpected exception",e );
                   } finally {
                       observer.shutdown();
                       setObserver(null);
                       setPeerState(ServerState.LOOKING);
                   }
                   break;
               case FOLLOWING:
                   try {
                       LOG.info("FOLLOWING");
                       setFollower(makeFollower(logFactory));
                       follower.followLeader();
                   } catch (Exception e) {
                       LOG.warn("Unexpected exception",e);
                   } finally {
                       follower.shutdown();
                       setFollower(null);
                       setPeerState(ServerState.LOOKING);
                   }
                   break;
               case LEADING:
                   LOG.info("LEADING");
                   try {
                       setLeader(makeLeader(logFactory));
                       leader.lead();
                       setLeader(null);
                   } catch (Exception e) {
                       LOG.warn("Unexpected exception",e);
                   } finally {
                       if (leader != null) {
                           leader.shutdown("Forcing shutdown");
                           setLeader(null);
                       }
                       setPeerState(ServerState.LOOKING);
                   }
                   break;
               }
           }
       }
   }
http://blog.csdn.net/xhh198781/article/details/10949697