Optimize zookeeper block logic on app startup

dubbo-common/src/main/java/com/alibaba/dubbo/common/concurrent/ExecutionList.java

@@ -2,8 +2,10 @@
 
 import com.alibaba.dubbo.common.logger.Logger;
 import com.alibaba.dubbo.common.logger.LoggerFactory;
+import com.alibaba.dubbo.common.utils.NamedThreadFactory;
 
 import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
 
 /**
  * <p>A list of listeners, each with an associated {@code Executor}, that
@@ -35,6 +37,8 @@ public final class ExecutionList {
 
     private boolean executed;
 
+    private static final Executor DEFAULT_EXECUTOR = Executors.newSingleThreadExecutor(new NamedThreadFactory("DubboFutureCallbackDefaultExecutor", true));
+
     /**
      * Creates a new, empty {@link ExecutionList}.
      */
@@ -63,9 +67,12 @@ public void add(Runnable runnable, Executor executor) {
         // Fail fast on a null.  We throw NPE here because the contract of
         // Executor states that it throws NPE on null listener, so we propagate
         // that contract up into the add method as well.
-        if (runnable == null || executor == null) {
+        if (runnable == null) {
             throw new NullPointerException("Both Runnable and Executor can not be null!");
         }
+        if (executor == null) {
+            executor = DEFAULT_EXECUTOR;
+        }
 
         // Lock while we check state.  We must maintain the lock while adding the
         // new pair so that another thread can't run the list out from under us.

dubbo-common/src/main/java/com/alibaba/dubbo/common/concurrent/ListenableFuture.java

@@ -116,4 +116,6 @@ public interface ListenableFuture<V> extends Future<V> {
      *                                    immediately but the executor rejected it.
      */
     void addListener(Runnable listener, Executor executor);
+
+    void addListener(Runnable listener);
 }

dubbo-common/src/main/java/com/alibaba/dubbo/common/concurrent/ListenableFutureTask.java

@@ -65,6 +65,11 @@ public void addListener(Runnable listener, Executor exec) {
         executionList.add(listener, exec);
     }
 
+    @Override
+    public void addListener(Runnable listener) {
+        executionList.add(listener, null);
+    }
+
     /**
      * Internal implementation detail used to invoke the listeners.
      */

dubbo-common/src/main/java/com/alibaba/dubbo/common/utils/Assert.java

@@ -30,4 +30,10 @@ public static void notNull(Object obj, String message) {
         }
     }
 
+    public static void notNull(Object obj, RuntimeException exeception) {
+        if (obj == null) {
+            throw exeception;
+        }
+    }
+
 }

dubbo-monitor/dubbo-monitor-api/src/main/java/com/alibaba/dubbo/monitor/support/AbstractMonitorFactory.java

@@ -80,7 +80,7 @@ public Monitor getMonitor(URL url) {
 
             final URL monitorUrl = url;
             final ListenableFutureTask<Monitor> listenableFutureTask = ListenableFutureTask.create(new MonitorCreator(monitorUrl));
-            listenableFutureTask.addListener(new MonitorListener(key), executor);
+            listenableFutureTask.addListener(new MonitorListener(key));
             executor.execute(listenableFutureTask);
             FUTURES.put(key, listenableFutureTask);
 

dubbo-remoting/dubbo-remoting-zookeeper/src/main/java/com/alibaba/dubbo/remoting/zookeeper/curator/CuratorZookeeperClient.java

@@ -27,7 +27,7 @@ public CuratorZookeeperClient(URL url) {
         try {
             CuratorFrameworkFactory.Builder builder = CuratorFrameworkFactory.builder()
                     .connectString(url.getBackupAddress())
-                    .retryPolicy(new RetryNTimes(Integer.MAX_VALUE, 1000))
+                    .retryPolicy(new RetryNTimes(1, 1000))
                     .connectionTimeoutMs(5000);
             String authority = url.getAuthority();
             if (authority != null && authority.length() > 0) {

dubbo-remoting/dubbo-remoting-zookeeper/src/main/java/com/alibaba/dubbo/remoting/zookeeper/zkclient/ZkClientWrapper.java

@@ -0,0 +1,124 @@
+package com.alibaba.dubbo.remoting.zookeeper.zkclient;
+
+import com.alibaba.dubbo.common.concurrent.ListenableFutureTask;
+import com.alibaba.dubbo.common.logger.Logger;
+import com.alibaba.dubbo.common.logger.LoggerFactory;
+import com.alibaba.dubbo.common.utils.Assert;
+
+import org.I0Itec.zkclient.IZkChildListener;
+import org.I0Itec.zkclient.IZkStateListener;
+import org.I0Itec.zkclient.ZkClient;
+import org.apache.zookeeper.Watcher.Event.KeeperState;
+
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * 连接超时后，能自动监听连接状态的zkclient包装类
+ * 也为和curator在使用上总体保持一致
+ * @author ken.lj
+ * @date 2017/10/29
+ */
+public class ZkClientWrapper {
+    Logger logger = LoggerFactory.getLogger(ZkClientWrapper.class);
+
+    private long timeout;
+    private ZkClient client;
+    private volatile KeeperState state;
+    private ListenableFutureTask<ZkClient> listenableFutureTask;
+    private volatile boolean started = false;
+
+
+    public ZkClientWrapper(final String serverAddr, long timeout) {
+        this.timeout = timeout;
+        listenableFutureTask = ListenableFutureTask.create(new Callable<ZkClient>() {
+            @Override
+            public ZkClient call() throws Exception {
+                return new ZkClient(serverAddr, Integer.MAX_VALUE);
+            }
+        });
+    }
+
+    public void start() {
+        if (!started) {
+            Thread connectThread = new Thread(listenableFutureTask);
+            connectThread.setName("DubboZkclientConnector");
+            connectThread.setDaemon(true);
+            connectThread.start();
+            try {
+                client = listenableFutureTask.get(timeout, TimeUnit.MILLISECONDS);
+            } catch (Throwable t) {
+                logger.error("Timeout! zookeeper server can not be connected in : " + timeout + "ms!", t);
+            }
+            started = true;
+        } else {
+            throw new IllegalStateException("Zkclient has already been started!");
+        }
+    }
+
+    public void addListener(final IZkStateListener listener) {
+        listenableFutureTask.addListener(new Runnable() {
+            @Override
+            public void run() {
+                try {
+                    client = listenableFutureTask.get();
+                    client.subscribeStateChanges(listener);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                } catch (ExecutionException e) {
+                    e.printStackTrace();
+                }
+            }
+        });
+    }
+
+    public boolean isConnected() {
+        return client != null && state == KeeperState.SyncConnected;
+    }
+
+    public void createPersistent(String path) {
+        Assert.notNull(client, new IllegalStateException("Zookeeper is not connected!"));
+        client.createPersistent(path, true);
+    }
+
+    public void createEphemeral(String path) {
+        Assert.notNull(client, new IllegalStateException("Zookeeper is not connected!"));
+        client.createEphemeral(path);
+    }
+
+    public void delete(String path) {
+        if (client == null) {
+            throw new IllegalStateException("Zookeeper is not connected!");
+        }
+        client.delete(path);
+    }
+
+    public List<String> getChildren(String path) {
+        Assert.notNull(client, new IllegalStateException("Zookeeper is not connected!"));
+        return client.getChildren(path);
+    }
+
+    public boolean exists(String path) {
+        Assert.notNull(client, new IllegalStateException("Zookeeper is not connected!"));
+        return client.exists(path);
+    }
+
+    public void close() {
+        Assert.notNull(client, new IllegalStateException("Zookeeper is not connected!"));
+        client.close();
+    }
+
+    public List<String> subscribeChildChanges(String path, final IZkChildListener listener) {
+        Assert.notNull(client, new IllegalStateException("Zookeeper is not connected!"));
+        return client.subscribeChildChanges(path, listener);
+    }
+
+    public void unsubscribeChildChanges(String path, IZkChildListener listener) {
+        Assert.notNull(client, new IllegalStateException("Zookeeper is not connected!"));
+        client.unsubscribeChildChanges(path, listener);
+    }
+
+
+}

dubbo-remoting/dubbo-remoting-zookeeper/src/main/java/com/alibaba/dubbo/remoting/zookeeper/zkclient/ZkclientZookeeperClient.java

@@ -7,7 +7,6 @@
 
 import org.I0Itec.zkclient.IZkChildListener;
 import org.I0Itec.zkclient.IZkStateListener;
-import org.I0Itec.zkclient.ZkClient;
 import org.I0Itec.zkclient.exception.ZkNoNodeException;
 import org.I0Itec.zkclient.exception.ZkNodeExistsException;
 import org.apache.zookeeper.Watcher.Event.KeeperState;
@@ -16,14 +15,14 @@
 
 public class ZkclientZookeeperClient extends AbstractZookeeperClient<IZkChildListener> {
 
-    private final ZkClient client;
+    private final ZkClientWrapper client;
 
     private volatile KeeperState state = KeeperState.SyncConnected;
 
     public ZkclientZookeeperClient(URL url) {
         super(url);
-        client = new ZkClient(url.getBackupAddress());
-        client.subscribeStateChanges(new IZkStateListener() {
+        client = new ZkClientWrapper(url.getBackupAddress(), 30000);
+        client.addListener(new IZkStateListener() {
             public void handleStateChanged(KeeperState state) throws Exception {
                 ZkclientZookeeperClient.this.state = state;
                 if (state == KeeperState.Disconnected) {
@@ -37,11 +36,13 @@ public void handleNewSession() throws Exception {
                 stateChanged(StateListener.RECONNECTED);
             }
         });
+        client.start();
     }
 
+
     public void createPersistent(String path) {
         try {
-            client.createPersistent(path, true);
+            client.createPersistent(path);
         } catch (ZkNodeExistsException e) {
         }
     }