Java tutorial
/* * * Copyright 2011 Netflix, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */ package com.netflix.curator; import java.io.Closeable; import java.io.IOException; import java.util.Queue; import java.util.concurrent.ConcurrentLinkedQueue; import java.util.concurrent.atomic.AtomicBoolean; import java.util.concurrent.atomic.AtomicReference; import org.apache.commons.io.IOUtils; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.netflix.curator.drivers.TracerDriver; import com.netflix.curator.ensemble.EnsembleProvider; import com.netflix.curator.utils.DebugUtils; import com.netflix.curator.utils.ZookeeperFactory; class ConnectionState implements Watcher, Closeable { private static final int MAX_BACKGROUND_EXCEPTIONS = 10; private static final boolean LOG_EVENTS = Boolean.getBoolean(DebugUtils.PROPERTY_LOG_EVENTS); private final Logger log = LoggerFactory.getLogger(getClass()); private final HandleHolder zooKeeper; private final AtomicBoolean isConnected = new AtomicBoolean(false); private final EnsembleProvider ensembleProvider; private final int sessionTimeoutMs; private final int connectionTimeoutMs; private final AtomicReference<TracerDriver> tracer; private final Queue<Exception> backgroundExceptions = new ConcurrentLinkedQueue<Exception>(); private final Queue<Watcher> parentWatchers = new ConcurrentLinkedQueue<Watcher>(); private volatile long connectionStartMs = 0; ConnectionState(ZookeeperFactory zookeeperFactory, EnsembleProvider ensembleProvider, int sessionTimeoutMs, int connectionTimeoutMs, Watcher parentWatcher, AtomicReference<TracerDriver> tracer, boolean canBeReadOnly) { this.ensembleProvider = ensembleProvider; this.sessionTimeoutMs = sessionTimeoutMs; this.connectionTimeoutMs = connectionTimeoutMs; this.tracer = tracer; if (parentWatcher != null) { parentWatchers.offer(parentWatcher); } zooKeeper = new HandleHolder(zookeeperFactory, this, ensembleProvider, sessionTimeoutMs, canBeReadOnly); } ZooKeeper getZooKeeper() throws Exception { if (SessionFailRetryLoop.sessionForThreadHasFailed()) { throw new SessionFailRetryLoop.SessionFailedException(); } Exception exception = backgroundExceptions.poll(); if (exception != null) { log.error("Background exception caught", exception); tracer.get().addCount("background-exceptions", 1); throw exception; } boolean localIsConnected = isConnected.get(); if (!localIsConnected) { checkTimeouts(); } return zooKeeper.getZooKeeper(); } boolean isConnected() { return isConnected.get(); } void start() throws Exception { log.debug("Starting"); ensembleProvider.start(); reset(); } @Override public void close() throws IOException { log.debug("Closing"); IOUtils.closeQuietly(ensembleProvider); try { zooKeeper.closeAndClear(); } catch (Exception e) { throw new IOException(e); } finally { isConnected.set(false); } } void addParentWatcher(Watcher watcher) { parentWatchers.offer(watcher); } void removeParentWatcher(Watcher watcher) { parentWatchers.remove(watcher); } @Override public void process(WatchedEvent event) { if (LOG_EVENTS) { log.debug("ConnectState watcher: " + event); } for (Watcher parentWatcher : parentWatchers) { TimeTrace timeTrace = new TimeTrace("connection-state-parent-process", tracer.get()); parentWatcher.process(event); timeTrace.commit(); } boolean wasConnected = isConnected.get(); boolean newIsConnected = wasConnected; if (event.getType() == Watcher.Event.EventType.None) { newIsConnected = checkState(event.getState(), wasConnected); } if (newIsConnected != wasConnected) { isConnected.set(newIsConnected); connectionStartMs = System.currentTimeMillis(); } } EnsembleProvider getEnsembleProvider() { return ensembleProvider; } private synchronized void checkTimeouts() throws Exception { long elapsed = System.currentTimeMillis() - connectionStartMs; if (elapsed >= Math.min(sessionTimeoutMs, connectionTimeoutMs)) { if (zooKeeper.hasNewConnectionString()) { handleNewConnectionString(); } else if (elapsed > sessionTimeoutMs) { if (!Boolean.getBoolean(DebugUtils.PROPERTY_DONT_LOG_CONNECTION_ISSUES)) { log.warn(String.format( "Connection attempt unsuccessful after %d (greater than session timeout of %d). Resetting connection and trying again with a new connection.", elapsed, sessionTimeoutMs)); } reset(); } else { KeeperException.ConnectionLossException connectionLossException = new KeeperException.ConnectionLossException(); if (!Boolean.getBoolean(DebugUtils.PROPERTY_DONT_LOG_CONNECTION_ISSUES)) { log.error(String.format( "Connection timed out for connection string (%s) and timeout (%d) / elapsed (%d)", zooKeeper.getConnectionString(), connectionTimeoutMs, elapsed), connectionLossException); } tracer.get().addCount("connections-timed-out", 1); throw connectionLossException; } } } private synchronized void reset() throws Exception { log.debug("reset"); isConnected.set(false); connectionStartMs = System.currentTimeMillis(); zooKeeper.closeAndReset(); zooKeeper.getZooKeeper(); // initiate connection } private boolean checkState(Event.KeeperState state, boolean wasConnected) { boolean isConnected = wasConnected; boolean checkNewConnectionString = true; switch (state) { default: case Disconnected: { isConnected = false; break; } case SyncConnected: case ConnectedReadOnly: { isConnected = true; break; } case AuthFailed: { isConnected = false; log.error("Authentication failed"); break; } case Expired: { isConnected = false; checkNewConnectionString = false; handleExpiredSession(); break; } case SaslAuthenticated: { // NOP break; } } if (checkNewConnectionString && zooKeeper.hasNewConnectionString()) { handleNewConnectionString(); } return isConnected; } private void handleNewConnectionString() { log.info("Connection string changed"); tracer.get().addCount("connection-string-changed", 1); try { reset(); } catch (Exception e) { queueBackgroundException(e); } } private void handleExpiredSession() { log.warn("Session expired event received"); tracer.get().addCount("session-expired", 1); try { reset(); } catch (Exception e) { queueBackgroundException(e); } } @SuppressWarnings({ "ThrowableResultOfMethodCallIgnored" }) private void queueBackgroundException(Exception e) { while (backgroundExceptions.size() >= MAX_BACKGROUND_EXCEPTIONS) { backgroundExceptions.poll(); } backgroundExceptions.offer(e); } }