我们知道在使用HBase的过程中首要的是和服务器端取得链接,那么客户端是如何去链接的,它是怎么找到master和regionserver的? 参与该过程中的主要
组件又有哪些?这些组件之间是如何协同工作的呢? 今天就让我们来一起解析.
HBase的连接代码很简单,如下:
try (Connection connection = ConnectionFactory.createConnection(conf))
这里用到了工厂模式进行Connection实例的创建,需要传入的是配置参数管理类Configuration,在创建中首先需要把用户信息添加进去:
if (user == null) {
UserProvider provider = UserProvider.instantiate(conf);
user = provider.getCurrent();
}
return createConnection(conf, false, pool, user);
String className = conf.get(HConnection.HBASE_CLIENT_CONNECTION_IMPL,
ConnectionManager.HConnectionImplementation.class.getName());
Class clazz = null;
try {
clazz = Class.forName(className);
} catch (ClassNotFoundException e) {
throw new IOException(e);
}
try {
// Default HCM#HCI is not accessible; make it so before invoking.
Constructor constructor =
clazz.getDeclaredConstructor(Configuration.class,
boolean.class, ExecutorService.class, User.class);
constructor.setAccessible(true);
return (Connection) constructor.newInstance(conf, managed, pool, user);
这里使用了反射技术进行类对象的构造,从代码中我们看到实际是调用了HConncetionImplementation的构造函数,这些类之间的相互关系如下图所示:
从途中可以看出,HConnectionImplementation是实际的Connction实现类,接下来我们去看看该类的实例化过程:
HConnectionImplementation(Configuration conf, boolean managed,
ExecutorService pool, User user) throws IOException {
this(conf);
this.user = user;
this.batchPool = pool;
this.managed = managed;
this.registry = setupRegistry();
retrieveClusterId();
this.rpcClient = RpcClientFactory.createClient(this.conf, this.clusterId);
this.rpcControllerFactory = RpcControllerFactory.instantiate(conf);
// Do we publish the status?
boolean shouldListen = conf.getBoolean(HConstants.STATUS_PUBLISHED,
HConstants.STATUS_PUBLISHED_DEFAULT);
Class listenerClass =
conf.getClass(ClusterStatusListener.STATUS_LISTENER_CLASS,
ClusterStatusListener.DEFAULT_STATUS_LISTENER_CLASS,
ClusterStatusListener.Listener.class);
if (shouldListen) {
if (listenerClass == null) {
LOG.warn(HConstants.STATUS_PUBLISHED + " is true, but " +
ClusterStatusListener.STATUS_LISTENER_CLASS + " is not set - not listening status");
} else {
clusterStatusListener = new ClusterStatusListener(
new ClusterStatusListener.DeadServerHandler() {
@Override
public void newDead(ServerName sn) {
clearCaches(sn);
rpcClient.cancelConnections(sn);
}
}, conf, listenerClass);
}
}
}
好吧这看起来有点小复杂,它首先调用了另一个构造类
protected HConnectionImplementation(Configuration conf) {
this.conf = conf;
this.tableConfig = new TableConfiguration(conf);
this.closed = false;
this.pause = conf.getLong(HConstants.HBASE_CLIENT_PAUSE,
HConstants.DEFAULT_HBASE_CLIENT_PAUSE);
this.numTries = tableConfig.getRetriesNumber();
this.rpcTimeout = conf.getInt(
HConstants.HBASE_RPC_TIMEOUT_KEY,
HConstants.DEFAULT_HBASE_RPC_TIMEOUT);
if (conf.getBoolean(CLIENT_NONCES_ENABLED_KEY, true)) {
synchronized (nonceGeneratorCreateLock) {
if (ConnectionManager.nonceGenerator == null) {
ConnectionManager.nonceGenerator = new PerClientRandomNonceGenerator();
}
this.nonceGenerator = ConnectionManager.nonceGenerator;
}
} else {
this.nonceGenerator = new NoNonceGenerator();
}
stats = ServerStatisticTracker.create(conf);
this.asyncProcess = createAsyncProcess(this.conf);
this.interceptor = (new Retr