Java tutorial
package org.apache.blur.thrift; /** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ import java.io.IOException; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.util.Collection; import java.util.Collections; import java.util.List; import java.util.Map; import java.util.Random; import java.util.concurrent.BlockingQueue; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicInteger; import org.apache.blur.thirdparty.thrift_0_9_0.async.AsyncMethodCallback; import org.apache.blur.thirdparty.thrift_0_9_0.async.TAsyncClient; import org.apache.blur.thirdparty.thrift_0_9_0.async.TAsyncClientManager; import org.apache.blur.thirdparty.thrift_0_9_0.protocol.TBinaryProtocol; import org.apache.blur.thirdparty.thrift_0_9_0.protocol.TProtocolFactory; import org.apache.blur.thirdparty.thrift_0_9_0.transport.TNonblockingSocket; import org.apache.blur.thirdparty.thrift_0_9_0.transport.TNonblockingTransport; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class AsyncClientPool { public static final Log LOG = LogFactory.getLog(AsyncClientPool.class); public static final int DEFAULT_MAX_CONNECTIONS_PER_HOST = 5; public static final int DEFAULT_CONNECTION_TIMEOUT = 60000; private int _maxConnectionsPerHost; private long _timeout; private long _pollTime = 5; private Map<String, AtomicInteger> _numberOfConnections = new ConcurrentHashMap<String, AtomicInteger>(); private Map<Connection, BlockingQueue<TAsyncClient>> _clientMap = new ConcurrentHashMap<Connection, BlockingQueue<TAsyncClient>>(); private Map<String, Constructor<?>> _constructorCache = new ConcurrentHashMap<String, Constructor<?>>(); private TProtocolFactory _protocolFactory; private TAsyncClientManager _clientManager; private Collection<TNonblockingTransport> _transports = new LinkedBlockingQueue<TNonblockingTransport>(); private Field _transportField; private Random random = new Random(); public AsyncClientPool() throws IOException { this(DEFAULT_MAX_CONNECTIONS_PER_HOST, DEFAULT_CONNECTION_TIMEOUT); } public AsyncClientPool(int maxConnectionsPerHost, int connectionTimeout) throws IOException { _clientManager = new TAsyncClientManager(); _protocolFactory = new TBinaryProtocol.Factory(); _maxConnectionsPerHost = maxConnectionsPerHost; _timeout = connectionTimeout; try { _transportField = TAsyncClient.class.getDeclaredField("___transport"); _transportField.setAccessible(true); } catch (SecurityException e) { throw new RuntimeException(e); } catch (NoSuchFieldException e) { throw new RuntimeException(e); } } public void close() { _clientManager.stop(); for (TNonblockingTransport transport : _transports) { transport.close(); } } /** * Gets a client instance that implements the AsyncIface interface that * connects to the given connection string. * * @param <T> * @param asyncIfaceClass * the AsyncIface interface to pool. * @param connectionStr * the connection string. * @return the client instance. */ @SuppressWarnings("unchecked") public <T> T getClient(final Class<T> asyncIfaceClass, final String connectionStr) { List<Connection> connections = BlurClientManager.getConnections(connectionStr); Collections.shuffle(connections, random); // randomness ftw final Connection connection = connections.get(0); return (T) Proxy.newProxyInstance(asyncIfaceClass.getClassLoader(), new Class[] { asyncIfaceClass }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return execute(new AsyncCall(asyncIfaceClass, method, args, connection)); } }); } private Object execute(AsyncCall call) throws Exception { AsyncMethodCallback<?> realCallback = getRealAsyncMethodCallback(call._args); TAsyncClient client = newClient(call._clazz, call._connection); AsyncMethodCallback<?> retryingCallback = wrapCallback(realCallback, client, call._connection); resetArgs(call._args, retryingCallback); return call._method.invoke(client, call._args); } private synchronized BlockingQueue<TAsyncClient> getQueue(Connection connection) { BlockingQueue<TAsyncClient> blockingQueue = _clientMap.get(connection); if (blockingQueue == null) { blockingQueue = new LinkedBlockingQueue<TAsyncClient>(); _clientMap.put(connection, blockingQueue); } return blockingQueue; } private void returnClient(Connection connection, TAsyncClient client) throws InterruptedException { if (!client.hasError()) { getQueue(connection).put(client); } else { AtomicInteger counter = _numberOfConnections.get(connection.getHost()); if (counter != null) { counter.decrementAndGet(); } } } @SuppressWarnings({ "rawtypes", "unchecked" }) private AsyncMethodCallback<?> wrapCallback(AsyncMethodCallback<?> realCallback, TAsyncClient client, Connection connectionStr) { return new ClientPoolAsyncMethodCallback(realCallback, client, this, connectionStr); } private void resetArgs(Object[] args, AsyncMethodCallback<?> callback) { args[args.length - 1] = callback; } private AsyncMethodCallback<?> getRealAsyncMethodCallback(Object[] args) { return (AsyncMethodCallback<?>) args[args.length - 1]; } private TAsyncClient newClient(Class<?> c, Connection connection) throws InterruptedException { BlockingQueue<TAsyncClient> blockingQueue = getQueue(connection); TAsyncClient client = blockingQueue.poll(); if (client != null) { return client; } AtomicInteger counter; synchronized (_numberOfConnections) { counter = _numberOfConnections.get(connection.getHost()); if (counter == null) { counter = new AtomicInteger(); _numberOfConnections.put(connection.getHost(), counter); } } synchronized (counter) { int numOfConnections = counter.get(); while (numOfConnections >= _maxConnectionsPerHost) { client = blockingQueue.poll(_pollTime, TimeUnit.MILLISECONDS); if (client != null) { return client; } LOG.debug("Waiting for client number of connection [" + numOfConnections + "], max connection per host [" + _maxConnectionsPerHost + "]"); numOfConnections = counter.get(); } LOG.info("Creating a new client for [" + connection + "]"); String name = c.getName(); Constructor<?> constructor = _constructorCache.get(name); if (constructor == null) { String clientClassName = name.replace("$AsyncIface", "$AsyncClient"); try { Class<?> clazz = Class.forName(clientClassName); constructor = clazz.getConstructor(new Class[] { TProtocolFactory.class, TAsyncClientManager.class, TNonblockingTransport.class }); _constructorCache.put(name, constructor); } catch (Exception e) { throw new RuntimeException(e); } } try { TNonblockingSocket transport = newTransport(connection); client = (TAsyncClient) constructor .newInstance(new Object[] { _protocolFactory, _clientManager, transport }); client.setTimeout(_timeout); counter.incrementAndGet(); return client; } catch (Exception e) { throw new RuntimeException(e); } } } private TNonblockingSocket newTransport(Connection connection) throws IOException { return new TNonblockingSocket(connection.getHost(), connection.getPort()); } private static class ClientPoolAsyncMethodCallback<T> implements AsyncMethodCallback<T> { private AsyncMethodCallback<T> _realCallback; private TAsyncClient _client; private AsyncClientPool _pool; private Connection _connection; public ClientPoolAsyncMethodCallback(AsyncMethodCallback<T> realCallback, TAsyncClient client, AsyncClientPool pool, Connection connection) { _realCallback = realCallback; _client = client; _pool = pool; _connection = connection; } @Override public void onComplete(T response) { _realCallback.onComplete(response); try { _pool.returnClient(_connection, _client); } catch (InterruptedException e) { throw new RuntimeException(e); } } @Override public void onError(Exception exception) { AtomicInteger counter = _pool._numberOfConnections.get(_connection.getHost()); if (counter != null) { counter.decrementAndGet(); } _realCallback.onError(exception); _pool.closeAndRemoveTransport(_client); } } private static class AsyncCall { Class<?> _clazz; Method _method; Object[] _args; Connection _connection; public AsyncCall(Class<?> clazz, Method method, Object[] args, Connection connection) { _clazz = clazz; _method = method; _args = args; _connection = connection; } } private void closeAndRemoveTransport(TAsyncClient client) { try { TNonblockingTransport transport = (TNonblockingTransport) _transportField.get(client); _transports.remove(transport); transport.close(); } catch (IllegalArgumentException e) { throw new RuntimeException(e); } catch (IllegalAccessException e) { throw new RuntimeException(e); } } }