Source Code Cross Referenced for ServerConnection.java in  » Web-Mail » james-2.3.1 » org » apache » james » util » connection » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Web Mail » james 2.3.1 » org.apache.james.util.connection 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /****************************************************************
002:         * Licensed to the Apache Software Foundation (ASF) under one   *
003:         * or more contributor license agreements.  See the NOTICE file *
004:         * distributed with this work for additional information        *
005:         * regarding copyright ownership.  The ASF licenses this file   *
006:         * to you under the Apache License, Version 2.0 (the            *
007:         * "License"); you may not use this file except in compliance   *
008:         * with the License.  You may obtain a copy of the License at   *
009:         *                                                              *
010:         *   http://www.apache.org/licenses/LICENSE-2.0                 *
011:         *                                                              *
012:         * Unless required by applicable law or agreed to in writing,   *
013:         * software distributed under the License is distributed on an  *
014:         * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
015:         * KIND, either express or implied.  See the License for the    *
016:         * specific language governing permissions and limitations      *
017:         * under the License.                                           *
018:         ****************************************************************/package org.apache.james.util.connection;
019:
020:        import java.io.IOException;
021:        import java.io.InterruptedIOException;
022:        import java.net.ServerSocket;
023:        import java.net.Socket;
024:        import java.net.SocketException;
025:        import java.util.ArrayList;
026:        import java.util.Iterator;
027:
028:        import org.apache.avalon.cornerstone.services.connection.ConnectionHandler;
029:        import org.apache.avalon.cornerstone.services.connection.ConnectionHandlerFactory;
030:        import org.apache.avalon.excalibur.pool.HardResourceLimitingPool;
031:        import org.apache.avalon.excalibur.pool.ObjectFactory;
032:        import org.apache.avalon.excalibur.pool.Pool;
033:        import org.apache.avalon.excalibur.pool.Poolable;
034:        import org.apache.excalibur.thread.ThreadPool;
035:        import org.apache.avalon.framework.activity.Initializable;
036:        import org.apache.avalon.framework.container.ContainerUtil;
037:        import org.apache.avalon.framework.logger.AbstractLogEnabled;
038:
039:        /**
040:         * Represents a single server socket managed by a connection manager.
041:         * The connection manager will spawn a single ServerConnection for each
042:         * server socket that the connection manager is managing.
043:         *
044:         */
045:        public class ServerConnection extends AbstractLogEnabled implements 
046:                Initializable, Runnable {
047:
048:            /**
049:             * This is a hack to deal with the fact that there appears to be
050:             * no platform-independent way to break out of a ServerSocket
051:             * accept() call.  On some platforms closing either the ServerSocket
052:             * itself, or its associated InputStream, causes the accept
053:             * method to exit.  Unfortunately, this behavior is not consistent
054:             * across platforms.  The deal with this, we introduce a polling
055:             * loop of 20 seconds for the server socket.  This introduces a
056:             * cost across platforms, but is necessary to maintain cross-platform
057:             * functionality.
058:             */
059:            private static int POLLING_INTERVAL = 20 * 1000;
060:
061:            /**
062:             * The server socket which this connection is managing
063:             */
064:            private ServerSocket serverSocket;
065:
066:            /**
067:             * The connection handler factory that generates connection
068:             * handlers to manage client connections to this server socket
069:             */
070:            private ConnectionHandlerFactory handlerFactory;
071:
072:            /**
073:             * The pool that produces ClientConnectionRunners
074:             */
075:            private Pool runnerPool;
076:
077:            /**
078:             * The factory used to provide ClientConnectionRunner objects
079:             */
080:            private ObjectFactory theRunnerFactory = new ClientConnectionRunnerFactory();
081:
082:            /**
083:             * The thread pool used to spawn individual threads used to manage each
084:             * client connection.
085:             */
086:            private ThreadPool connThreadPool;
087:
088:            /**
089:             * The timeout for client sockets spawned off this connection.
090:             */
091:            private int socketTimeout;
092:
093:            /**
094:             * The maximum number of open client connections that this server
095:             * connection will allow.
096:             */
097:            private int maxOpenConn;
098:
099:            /**
100:             * A collection of client connection runners.
101:             */
102:            private final ArrayList clientConnectionRunners = new ArrayList();
103:
104:            /**
105:             * The thread used to manage this server connection.
106:             */
107:            private Thread serverConnectionThread;
108:
109:            /**
110:             * The sole constructor for a ServerConnection.
111:             *
112:             * @param serverSocket the ServerSocket associated with this ServerConnection
113:             * @param handlerFactory the factory that generates ConnectionHandlers for the client
114:             *                       connections spawned off this ServerConnection
115:             * @param threadPool the ThreadPool used to obtain handler threads
116:             * @param timeout the client idle timeout for this ServerConnection's client connections
117:             * @param maxOpenConn the maximum number of open client connections allowed for this
118:             *                    ServerConnection
119:             */
120:            public ServerConnection(ServerSocket serverSocket,
121:                    ConnectionHandlerFactory handlerFactory,
122:                    ThreadPool threadPool, int timeout, int maxOpenConn) {
123:                this .serverSocket = serverSocket;
124:                this .handlerFactory = handlerFactory;
125:                connThreadPool = threadPool;
126:                socketTimeout = timeout;
127:                this .maxOpenConn = maxOpenConn;
128:            }
129:
130:            /**
131:             * @see org.apache.avalon.framework.activity.Initializable#initialize()
132:             */
133:            public void initialize() throws Exception {
134:                runnerPool = new HardResourceLimitingPool(theRunnerFactory, 5,
135:                        maxOpenConn);
136:                ContainerUtil.enableLogging(runnerPool, getLogger());
137:                ContainerUtil.initialize(runnerPool);
138:            }
139:
140:            /**
141:             * The dispose operation is called by the owning ConnectionManager
142:             * at the end of its lifecycle.  Cleans up the server connection, forcing
143:             * everything to finish.
144:             */
145:            public void dispose() {
146:                if (getLogger().isDebugEnabled()) {
147:                    getLogger().debug(
148:                            "Disposing server connection..." + this .toString());
149:                }
150:                synchronized (this ) {
151:                    if (null != serverConnectionThread) {
152:                        // Execution of this block means that the run() method
153:                        // hasn't finished yet.  So we interrupt the thread
154:                        // to terminate run() and wait for the run() method
155:                        // to finish.  The notifyAll() at the end of run() will
156:                        // wake this thread and allow dispose() to end.
157:                        Thread thread = serverConnectionThread;
158:                        serverConnectionThread = null;
159:                        thread.interrupt();
160:                        try {
161:                            serverSocket.close();
162:                        } catch (IOException ie) {
163:                            // Ignored - we're doing this to break out of the
164:                            // accept.  This minimizes the time required to
165:                            // shutdown the server.  Unfortunately, this is
166:                            // not guaranteed to work on all platforms.  See
167:                            // the comments for POLLING_INTERVAL
168:                        }
169:                        try {
170:                            if (POLLING_INTERVAL > 0) {
171:                                wait(2L * POLLING_INTERVAL);
172:                            } else {
173:                                wait();
174:                            }
175:                        } catch (InterruptedException ie) {
176:                            // Expected - just complete dispose()
177:                        }
178:                    }
179:                    ContainerUtil.dispose(runnerPool);
180:                    runnerPool = null;
181:                }
182:
183:                getLogger().debug(
184:                        "Closed server connection - cleaning up clients - "
185:                                + this .toString());
186:
187:                synchronized (clientConnectionRunners) {
188:                    Iterator runnerIterator = clientConnectionRunners
189:                            .iterator();
190:                    while (runnerIterator.hasNext()) {
191:                        ClientConnectionRunner runner = (ClientConnectionRunner) runnerIterator
192:                                .next();
193:                        runner.dispose();
194:                        runner = null;
195:                    }
196:                    clientConnectionRunners.clear();
197:                }
198:
199:                getLogger().debug("Cleaned up clients - " + this .toString());
200:
201:            }
202:
203:            /**
204:             * Returns a ClientConnectionRunner in the set managed by this ServerConnection object.
205:             *
206:             * @param clientConnectionRunner the ClientConnectionRunner to be added
207:             */
208:            private ClientConnectionRunner addClientConnectionRunner()
209:                    throws Exception {
210:                synchronized (clientConnectionRunners) {
211:                    ClientConnectionRunner clientConnectionRunner = (ClientConnectionRunner) runnerPool
212:                            .get();
213:                    clientConnectionRunners.add(clientConnectionRunner);
214:                    if (getLogger().isDebugEnabled()) {
215:                        getLogger().debug(
216:                                "Adding one connection for a total of "
217:                                        + clientConnectionRunners.size());
218:                    }
219:                    return clientConnectionRunner;
220:                }
221:            }
222:
223:            /**
224:             * Removes a ClientConnectionRunner from the set managed by this ServerConnection object.
225:             *
226:             * @param clientConnectionRunner the ClientConnectionRunner to be removed
227:             */
228:            private void removeClientConnectionRunner(
229:                    ClientConnectionRunner clientConnectionRunner) {
230:
231:                /*
232:                 * checking runnerPool avoids 'dead-lock' when service is disposing :
233:                 * (dispose() calls dispose all runners)
234:                 * but runner is 'running' and cleans up on exit
235:                 * this situation will result in a dead-lock on 'clientConnectionRunners'
236:                 */
237:                if (runnerPool == null) {
238:                    getLogger()
239:                            .info(
240:                                    "ServerConnection.removeClientConnectionRunner - dispose has been called - so just return : "
241:                                            + clientConnectionRunner);
242:                    return;
243:                }
244:
245:                synchronized (clientConnectionRunners) {
246:                    if (clientConnectionRunners.remove(clientConnectionRunner)) {
247:                        if (getLogger().isDebugEnabled()) {
248:                            getLogger().debug(
249:                                    "Releasing one connection, leaving a total of "
250:                                            + clientConnectionRunners.size());
251:                        }
252:                        runnerPool.put(clientConnectionRunner);
253:                    }
254:                }
255:
256:                synchronized (this ) {
257:                    notify();
258:                } // match the wait(...) in the run() inner loop before accept().
259:            }
260:
261:            /**
262:             * Provides the body for the thread of execution for a ServerConnection.
263:             * Connections made to the server socket are passed to an appropriate,
264:             * newly created, ClientConnectionRunner
265:             */
266:            public void run() {
267:                serverConnectionThread = Thread.currentThread();
268:
269:                int ioExceptionCount = 0;
270:                try {
271:                    serverSocket.setSoTimeout(POLLING_INTERVAL);
272:                } catch (SocketException se) {
273:                    // Ignored - for the moment
274:                }
275:
276:                if ((getLogger().isDebugEnabled())
277:                        && (serverConnectionThread != null)) {
278:                    StringBuffer debugBuffer = new StringBuffer(128).append(
279:                            serverConnectionThread.getName()).append(
280:                            " is listening on ")
281:                            .append(serverSocket.toString());
282:                    getLogger().debug(debugBuffer.toString());
283:                }
284:                while (!Thread.currentThread().interrupted()
285:                        && null != serverConnectionThread) {
286:                    try {
287:                        Socket clientSocket = null;
288:                        try {
289:                            while (maxOpenConn > 0
290:                                    && clientConnectionRunners.size() >= maxOpenConn) {
291:                                getLogger().warn(
292:                                        "Maximum number of open connections ("
293:                                                + clientConnectionRunners
294:                                                        .size() + ") in use.");
295:                                synchronized (this ) {
296:                                    wait(10000);
297:                                }
298:                            }
299:
300:                            clientSocket = serverSocket.accept();
301:
302:                        } catch (InterruptedIOException iioe) {
303:                            // This exception is expected upon ServerConnection shutdown.
304:                            // See the POLLING_INTERVAL comment
305:                            continue;
306:                        } catch (IOException se) {
307:                            if (ioExceptionCount > 0) {
308:                                getLogger()
309:                                        .error(
310:                                                "Fatal exception while listening on server socket.  Terminating connection.",
311:                                                se);
312:                                break;
313:                            } else {
314:                                continue;
315:                            }
316:                        } catch (SecurityException se) {
317:                            getLogger()
318:                                    .error(
319:                                            "Fatal exception while listening on server socket.  Terminating connection.",
320:                                            se);
321:                            break;
322:                        }
323:                        ClientConnectionRunner runner = null;
324:                        synchronized (clientConnectionRunners) {
325:                            if ((maxOpenConn > 0)
326:                                    && (clientConnectionRunners.size() >= maxOpenConn)) {
327:                                if (getLogger().isWarnEnabled()) {
328:                                    getLogger()
329:                                            .warn(
330:                                                    "Maximum number of open connections exceeded - refusing connection.  Current number of connections is "
331:                                                            + clientConnectionRunners
332:                                                                    .size());
333:                                    if (getLogger().isWarnEnabled()) {
334:                                        Iterator runnerIterator = clientConnectionRunners
335:                                                .iterator();
336:                                        getLogger().info("Connections: ");
337:                                        while (runnerIterator.hasNext()) {
338:                                            getLogger()
339:                                                    .info(
340:                                                            "    "
341:                                                                    + ((ClientConnectionRunner) runnerIterator
342:                                                                            .next())
343:                                                                            .toString());
344:                                        }
345:                                    }
346:                                }
347:                                try {
348:                                    clientSocket.close();
349:                                } catch (IOException ignored) {
350:                                    // We ignore this exception, as we already have an error condition.
351:                                }
352:                                continue;
353:                            } else {
354:                                clientSocket.setSoTimeout(socketTimeout);
355:                                runner = addClientConnectionRunner();
356:                                runner.setSocket(clientSocket);
357:                            }
358:                        }
359:                        setupLogger(runner);
360:                        try {
361:                            connThreadPool.execute(runner);
362:                        } catch (Exception e) {
363:                            // This error indicates that the underlying thread pool
364:                            // is out of threads.  For robustness, we catch this and
365:                            // cleanup
366:                            getLogger()
367:                                    .error(
368:                                            "Internal error - insufficient threads available to service request.  "
369:                                                    + Thread.activeCount()
370:                                                    + " threads in service request pool.",
371:                                            e);
372:                            try {
373:                                clientSocket.close();
374:                            } catch (IOException ignored) {
375:                                // We ignore this exception, as we already have an error condition.
376:                            }
377:                            // In this case, the thread will not remove the client connection runner,
378:                            // so we must.
379:                            removeClientConnectionRunner(runner);
380:                        }
381:                    } catch (IOException ioe) {
382:                        getLogger()
383:                                .error("Exception accepting connection", ioe);
384:                    } catch (Throwable e) {
385:                        getLogger().error(
386:                                "Exception executing client connection runner: "
387:                                        + e.getMessage(), e);
388:                    }
389:                }
390:                synchronized (this ) {
391:                    serverConnectionThread = null;
392:                    Thread.currentThread().interrupted();
393:                    notifyAll();
394:                }
395:            }
396:
397:            /**
398:             * An inner class to provide the actual body of the thread of execution
399:             * that occurs upon a client connection.
400:             *
401:             */
402:            class ClientConnectionRunner extends AbstractLogEnabled implements 
403:                    Poolable, Runnable {
404:
405:                /**
406:                 * The Socket that this client connection is using for transport.
407:                 */
408:                private Socket clientSocket;
409:
410:                /**
411:                 * The thread of execution associated with this client connection.
412:                 */
413:                private Thread clientSocketThread;
414:
415:                /**
416:                 * Returns string for diagnostic logging
417:                 */
418:                public String toString() {
419:                    return getClass().getName() + " for " + clientSocket
420:                            + " on " + clientSocketThread;
421:                }
422:
423:                public ClientConnectionRunner() {
424:                }
425:
426:                /**
427:                 * The dispose operation that terminates the runner.  Should only be
428:                 * called by the ServerConnection that owns the ClientConnectionRunner
429:                 */
430:                public void dispose() {
431:                    synchronized (this ) {
432:                        if (null != clientSocketThread) {
433:                            // Execution of this block means that the run() method
434:                            // hasn't finished yet.  So we interrupt the thread
435:                            // to terminate run() and wait for the run() method
436:                            // to finish.  The notifyAll() at the end of run() will
437:                            // wake this thread and allow dispose() to end.
438:                            clientSocketThread.interrupt();
439:                            clientSocketThread = null;
440:                            try {
441:                                wait();
442:                            } catch (InterruptedException ie) {
443:                                // Expected - return from the method
444:                            }
445:                        }
446:                    }
447:                }
448:
449:                /**
450:                 * Sets the socket for a ClientConnectionRunner.
451:                 *
452:                 * @param socket the client socket associated with this ClientConnectionRunner
453:                 */
454:                public void setSocket(Socket socket) {
455:                    clientSocket = socket;
456:                }
457:
458:                /**
459:                 * Provides the body for the thread of execution dealing with a particular client
460:                 * connection.  An appropriate ConnectionHandler is created, applied, executed,
461:                 * and released.
462:                 */
463:                public void run() {
464:                    ConnectionHandler handler = null;
465:                    try {
466:                        clientSocketThread = Thread.currentThread();
467:
468:                        handler = ServerConnection.this .handlerFactory
469:                                .createConnectionHandler();
470:                        String connectionString = null;
471:                        if (getLogger().isDebugEnabled()) {
472:                            connectionString = getConnectionString();
473:                            String message = "Starting " + connectionString;
474:                            getLogger().debug(message);
475:                        }
476:
477:                        handler.handleConnection(clientSocket);
478:
479:                        if (getLogger().isDebugEnabled()) {
480:                            String message = "Ending " + connectionString;
481:                            getLogger().debug(message);
482:                        }
483:
484:                    } catch (Throwable e) {
485:                        getLogger().error("Error handling connection", e);
486:                    } finally {
487:
488:                        // Close the underlying socket
489:                        try {
490:                            if (clientSocket != null) {
491:                                clientSocket.close();
492:                            }
493:                        } catch (IOException ioe) {
494:                            getLogger().warn("Error shutting down connection",
495:                                    ioe);
496:                        }
497:
498:                        clientSocket = null;
499:
500:                        // Null out the thread, notify other threads to encourage
501:                        // a context switch
502:                        synchronized (this ) {
503:                            clientSocketThread = null;
504:
505:                            Thread.currentThread().interrupted();
506:
507:                            // Release the handler and kill the reference to the handler factory
508:                            //
509:                            // This needs to be done after the clientSocketThread is nulled out,
510:                            // otherwise we could trash a reused ClientConnectionRunner
511:                            if (handler != null) {
512:                                ServerConnection.this .handlerFactory
513:                                        .releaseConnectionHandler(handler);
514:                                handler = null;
515:                            }
516:
517:                            // Remove this runner from the list of active connections.
518:                            ServerConnection.this 
519:                                    .removeClientConnectionRunner(this );
520:
521:                            notifyAll();
522:                        }
523:                    }
524:                }
525:
526:                /**
527:                 * Helper method to return a formatted string with connection transport information.
528:                 *
529:                 * @return a formatted string
530:                 */
531:                private String getConnectionString() {
532:                    if (clientSocket == null) {
533:                        return "invalid socket";
534:                    }
535:                    StringBuffer connectionBuffer = new StringBuffer(256)
536:                            .append("connection on ").append(
537:                                    clientSocket.getLocalAddress()
538:                                            .getHostAddress().toString())
539:                            .append(":").append(clientSocket.getLocalPort())
540:                            .append(" from ").append(
541:                                    clientSocket.getInetAddress()
542:                                            .getHostAddress().toString())
543:                            .append(":").append(clientSocket.getPort());
544:                    return connectionBuffer.toString();
545:                }
546:            }
547:
548:            /**
549:             * The factory for producing handlers.
550:             */
551:            private class ClientConnectionRunnerFactory implements 
552:                    ObjectFactory {
553:
554:                /**
555:                 * @see org.apache.avalon.excalibur.pool.ObjectFactory#newInstance()
556:                 */
557:                public Object newInstance() throws Exception {
558:                    return new ClientConnectionRunner();
559:                }
560:
561:                /**
562:                 * @see org.apache.avalon.excalibur.pool.ObjectFactory#getCreatedClass()
563:                 */
564:                public Class getCreatedClass() {
565:                    return ClientConnectionRunner.class;
566:                }
567:
568:                /**
569:                 * @see org.apache.avalon.excalibur.pool.ObjectFactory#decommision(Object)
570:                 */
571:                public void decommission(Object object) throws Exception {
572:                    return;
573:                }
574:            }
575:        }
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