Zookeeper 源码分析-启动

Zookeeper 源码分析-启动

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• 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。

Java代码  

1. public class QuorumPeerMain {
2. protected QuorumPeer quorumPeer;
3. /**
4. * To start the replicated server specify the configuration file name on
5. * the command line.
6. * @param args path to the configfile
7. */
8. public static void main(String[] args) {
9. QuorumPeerMain main = new QuorumPeerMain();
10. main.initializeAndRun(args);
11. }
12. protected void initializeAndRun(String[] args)
13. throws ConfigException, IOException
14. {
15. runFromConfig(config);
16. }
17. public void runFromConfig(QuorumPeerConfig config) throws IOException {
18. LOG.info("Starting quorum peer");
19. try {
20. NIOServerCnxn.Factory cnxnFactory =
21. new NIOServerCnxn.Factory(config.getClientPortAddress(),
22. config.getMaxClientCnxns());
23. quorumPeer = new QuorumPeer();
24. quorumPeer.setClientPortAddress(config.getClientPortAddress());
25. quorumPeer.setTxnFactory(new FileTxnSnapLog(
26. new File(config.getDataLogDir()),
27. new File(config.getDataDir())));
28. quorumPeer.setQuorumPeers(config.getServers());
29. quorumPeer.setElectionType(config.getElectionAlg());
30. quorumPeer.setMyid(config.getServerId());
31. quorumPeer.setTickTime(config.getTickTime());
32. quorumPeer.setMinSessionTimeout(config.getMinSessionTimeout());
33. quorumPeer.setMaxSessionTimeout(config.getMaxSessionTimeout());
34. quorumPeer.setInitLimit(config.getInitLimit());
35. quorumPeer.setSyncLimit(config.getSyncLimit());
36. quorumPeer.setQuorumVerifier(config.getQuorumVerifier());
37. quorumPeer.setCnxnFactory(cnxnFactory);
38. quorumPeer.setZKDatabase(new ZKDatabase(quorumPeer.getTxnFactory()));
39. quorumPeer.setLearnerType(config.getPeerType());
40. quorumPeer.start();
41. quorumPeer.join();
42. } catch (InterruptedException e) {
43. // warn, but generally this is ok
44. LOG.warn("Quorum Peer interrupted", e);
45. }
46. }
47. }

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

Java代码  

1. @Override
2. public synchronized void start() {
3. try {
4. zkDb.loadDataBase();
5. } catch(IOException ie) {
6. LOG.fatal("Unable to load database on disk", ie);
7. throw new RuntimeException("Unable to run quorum server ", ie);
8. }
9. cnxnFactory.start(); //用于处理与client的交互
10. startLeaderElection();//开始选举算法
11. super.start();
12. }

调用loadDatabase从磁盘加载数据到内存

Java代码  

1. public long loadDataBase() throws IOException {
2. PlayBackListener listener=new PlayBackListener(){
3. public void onTxnLoaded(TxnHeader hdr,Record txn){
4. Request r = new Request(null, 0, hdr.getCxid(),hdr.getType(),
5. null, null);
6. r.txn = txn;
7. r.hdr = hdr;
8. r.zxid = hdr.getZxid();
9. addCommittedProposal(r);
10. }
11. };
12. long zxid = snapLog.restore(dataTree,sessionsWithTimeouts,listener);
13. initialized = true;
14. return zxid;
15. }

调用QuorumPeer的run函数，按照peer的state做不同的处理

Java代码  

1. @Override
2. public void run() {
3. setName("QuorumPeer:" + cnxnFactory.getLocalAddress());
4. try {
5. /*
6. * Main loop
7. */
8. while (running) {
9. switch (getPeerState()) {
10. case LOOKING:
11. try {
12. LOG.info("LOOKING");
13. setCurrentVote(makeLEStrategy().lookForLeader());
14. } catch (Exception e) {
15. LOG.warn("Unexpected exception",e);
16. setPeerState(ServerState.LOOKING);
17. }
18. break;
19. case OBSERVING:
20. try {
21. LOG.info("OBSERVING");
22. setObserver(makeObserver(logFactory));
23. observer.observeLeader();
24. } catch (Exception e) {
25. LOG.warn("Unexpected exception",e );
26. } finally {
27. observer.shutdown();
28. setObserver(null);
29. setPeerState(ServerState.LOOKING);
30. }
31. break;
32. case FOLLOWING:
33. try {
34. LOG.info("FOLLOWING");
35. setFollower(makeFollower(logFactory));
36. follower.followLeader();
37. } catch (Exception e) {
38. LOG.warn("Unexpected exception",e);
39. } finally {
40. follower.shutdown();
41. setFollower(null);
42. setPeerState(ServerState.LOOKING);
43. }
44. break;
45. case LEADING:
46. LOG.info("LEADING");
47. try {
48. setLeader(makeLeader(logFactory));
49. leader.lead();
50. setLeader(null);
51. } catch (Exception e) {
52. LOG.warn("Unexpected exception",e);
53. } finally {
54. if (leader != null) {
55. leader.shutdown("Forcing shutdown");
56. setLeader(null);
57. }
58. setPeerState(ServerState.LOOKING);
59. }
60. break;
61. }
62. }
63. }
64. }
65. http://blog.csdn.net/xhh198781/article/details/10949697