curator-client源码阅读笔记

Zookeeper官方client使用起来有很多不便，比如session expire之后需要使用一个新的ZooKeeper对象，提供的接口过于底层等等

Curator是对ZooKeeper的一个封装，其中curator-client是最底层的一个封装，主要是提供自动重连的功能


入口类 CuratorZookeeperClient本身是一个很简单的封装，只保存了retryPolicy和ensembleProvider，真正的连接管理都交给了ConnectionState来处理

Java代码

1. public CuratorZookeeperClient(ZookeeperFactory zookeeperFactory, EnsembleProvider ensembleProvider,int sessionTimeoutMs, int connectionTimeoutMs, Watcher watcher, RetryPolicy retryPolicy,boolean canBeReadOnly)
2. {
3. retryPolicy = Preconditions.checkNotNull(retryPolicy, "retryPolicy cannot be null");
4. ensembleProvider = Preconditions.checkNotNull(ensembleProvider, "ensembleProvider cannot be null");
6. this.connectionTimeoutMs = connectionTimeoutMs;
7. state = new ConnectionState(zookeeperFactory, ensembleProvider, sessionTimeoutMs, connectionTimeoutMs, watcher, tracer, canBeReadOnly);
8. setRetryPolicy(retryPolicy);
9. }

    public CuratorZookeeperClient(ZookeeperFactory zookeeperFactory, EnsembleProvider ensembleProvider, int sessionTimeoutMs, int connectionTimeoutMs, Watcher watcher, RetryPolicy retryPolicy, boolean canBeReadOnly)    {        retryPolicy = Preconditions.checkNotNull(retryPolicy, "retryPolicy cannot be null");        ensembleProvider = Preconditions.checkNotNull(ensembleProvider, "ensembleProvider cannot be null");        this.connectionTimeoutMs = connectionTimeoutMs;        state = new ConnectionState(zookeeperFactory, ensembleProvider, sessionTimeoutMs, connectionTimeoutMs, watcher, tracer, canBeReadOnly);        setRetryPolicy(retryPolicy);    }

ConnectionState

Java代码

1. class ConnectionState implements Watcher, Closeable
2. {
3. private volatile long connectionStartMs = 0;
5. private final Logger log = LoggerFactory.getLogger(getClass());
7. //负责管理Zookeeper连接
8. private final HandleHolder zooKeeper;
9. private final AtomicBoolean isConnected =new AtomicBoolean(false);
11. //zookeeper连接地址的provider
12. private final EnsembleProvider ensembleProvider;
13. private final int connectionTimeoutMs;
14. private final AtomicReference<TracerDriver> tracer;
16. private final Queue<Exception> backgroundExceptions =new ConcurrentLinkedQueue<Exception>();
18. 用户自定义的watcher
19. private final Queue<Watcher> parentWatchers =new ConcurrentLinkedQueue<Watcher>();
22. ConnectionState(ZookeeperFactory zookeeperFactory, EnsembleProvider ensembleProvider,int sessionTimeoutMs, int connectionTimeoutMs, Watcher parentWatcher, AtomicReference<TracerDriver> tracer,boolean canBeReadOnly)
23. {
24. this.ensembleProvider = ensembleProvider;
25. this.connectionTimeoutMs = connectionTimeoutMs;
26. this.tracer = tracer;
27. if ( parentWatcher != null )
28. {
29. parentWatchers.offer(parentWatcher);
30. }
32. //ZooKeeper真正的连接还是由HandleHolder来管理，注意到第二个参数watcher，使用的是this
33. zooKeeper = new HandleHolder(zookeeperFactory, this, ensembleProvider, sessionTimeoutMs, canBeReadOnly);
34. }
35. }

class ConnectionState implements Watcher, Closeable{    private volatile long connectionStartMs = 0;    private final Logger                        log = LoggerFactory.getLogger(getClass());    //负责管理Zookeeper连接    private final HandleHolder                  zooKeeper;    private final AtomicBoolean                 isConnected = new AtomicBoolean(false);        //zookeeper连接地址的provider    private final EnsembleProvider              ensembleProvider;    private final int                           connectionTimeoutMs;    private final AtomicReference<TracerDriver> tracer;    private final Queue<Exception>              backgroundExceptions = new ConcurrentLinkedQueue<Exception>();    用户自定义的watcher    private final Queue<Watcher>                parentWatchers = new ConcurrentLinkedQueue<Watcher>();        ConnectionState(ZookeeperFactory zookeeperFactory, EnsembleProvider ensembleProvider, int sessionTimeoutMs, int connectionTimeoutMs, Watcher parentWatcher, AtomicReference<TracerDriver> tracer, boolean canBeReadOnly)    {        this.ensembleProvider = ensembleProvider;        this.connectionTimeoutMs = connectionTimeoutMs;        this.tracer = tracer;        if ( parentWatcher != null )        {            parentWatchers.offer(parentWatcher);        }                //ZooKeeper真正的连接还是由HandleHolder来管理，注意到第二个参数watcher，使用的是this        zooKeeper = new HandleHolder(zookeeperFactory, this, ensembleProvider, sessionTimeoutMs, canBeReadOnly);    }}