001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core.appender;
018
019import java.io.Serializable;
020import java.util.ArrayList;
021import java.util.List;
022import java.util.Map;
023import java.util.concurrent.ArrayBlockingQueue;
024import java.util.concurrent.BlockingQueue;
025import java.util.concurrent.atomic.AtomicLong;
026
027import org.apache.logging.log4j.core.Appender;
028import org.apache.logging.log4j.core.Filter;
029import org.apache.logging.log4j.core.LogEvent;
030import org.apache.logging.log4j.core.async.RingBufferLogEvent;
031import org.apache.logging.log4j.core.config.AppenderControl;
032import org.apache.logging.log4j.core.config.AppenderRef;
033import org.apache.logging.log4j.core.config.Configuration;
034import org.apache.logging.log4j.core.config.ConfigurationException;
035import org.apache.logging.log4j.core.config.plugins.Plugin;
036import org.apache.logging.log4j.core.config.plugins.PluginAliases;
037import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
038import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
039import org.apache.logging.log4j.core.config.plugins.PluginElement;
040import org.apache.logging.log4j.core.config.plugins.PluginFactory;
041import org.apache.logging.log4j.core.impl.Log4jLogEvent;
042
043/**
044 * Appends to one or more Appenders asynchronously.  You can configure an
045 * AsyncAppender with one or more Appenders and an Appender to append to if the
046 * queue is full. The AsyncAppender does not allow a filter to be specified on
047 * the Appender references.
048 */
049@Plugin(name = "Async", category = "Core", elementType = "appender", printObject = true)
050public final class AsyncAppender extends AbstractAppender {
051
052    private static final long serialVersionUID = 1L;
053    private static final int DEFAULT_QUEUE_SIZE = 128;
054    private static final String SHUTDOWN = "Shutdown";
055
056    private final BlockingQueue<Serializable> queue;
057    private final int queueSize;
058    private final boolean blocking;
059    private final Configuration config;
060    private final AppenderRef[] appenderRefs;
061    private final String errorRef;
062    private final boolean includeLocation;
063    private AppenderControl errorAppender;
064    private AsyncThread thread;
065    private static final AtomicLong threadSequence = new AtomicLong(1);
066    private static ThreadLocal<Boolean> isAppenderThread = new ThreadLocal<>();
067
068
069    private AsyncAppender(final String name, final Filter filter, final AppenderRef[] appenderRefs,
070                           final String errorRef, final int queueSize, final boolean blocking,
071                           final boolean ignoreExceptions, final Configuration config,
072                           final boolean includeLocation) {
073        super(name, filter, null, ignoreExceptions);
074        this.queue = new ArrayBlockingQueue<>(queueSize);
075        this.queueSize = queueSize;
076        this.blocking = blocking;
077        this.config = config;
078        this.appenderRefs = appenderRefs;
079        this.errorRef = errorRef;
080        this.includeLocation = includeLocation;
081    }
082
083    @Override
084    public void start() {
085        final Map<String, Appender> map = config.getAppenders();
086        final List<AppenderControl> appenders = new ArrayList<>();
087        for (final AppenderRef appenderRef : appenderRefs) {
088            final Appender appender = map.get(appenderRef.getRef());
089            if (appender != null) {
090                appenders.add(new AppenderControl(appender, appenderRef.getLevel(), appenderRef.getFilter()));
091            } else {
092                LOGGER.error("No appender named {} was configured", appenderRef);
093            }
094        }
095        if (errorRef != null) {
096            final Appender appender = map.get(errorRef);
097            if (appender != null) {
098                errorAppender = new AppenderControl(appender, null, null);
099            } else {
100                LOGGER.error("Unable to set up error Appender. No appender named {} was configured", errorRef);
101            }
102        }
103        if (appenders.size() > 0) {
104            thread = new AsyncThread(appenders, queue);
105            thread.setName("AsyncAppender-" + getName());
106        } else if (errorRef == null) {
107            throw new ConfigurationException("No appenders are available for AsyncAppender " + getName());
108        }
109
110        thread.start();
111        super.start();
112    }
113
114    @Override
115    public void stop() {
116        super.stop();
117        LOGGER.trace("AsyncAppender stopping. Queue still has {} events.", queue.size());
118        thread.shutdown();
119        try {
120            thread.join();
121        } catch (final InterruptedException ex) {
122            LOGGER.warn("Interrupted while stopping AsyncAppender {}", getName());
123        }
124        LOGGER.trace("AsyncAppender stopped. Queue has {} events.", queue.size());
125    }
126
127    /**
128     * Actual writing occurs here.
129     * 
130     * @param logEvent
131     *        The LogEvent.
132     */
133    @Override
134    public void append(LogEvent logEvent) {
135        if (!isStarted()) {
136            throw new IllegalStateException("AsyncAppender " + getName() + " is not active");
137        }
138        if (!(logEvent instanceof Log4jLogEvent)) {
139            if (!(logEvent instanceof RingBufferLogEvent)) {
140                return; // only know how to Serialize Log4jLogEvents and RingBufferLogEvents
141            }
142            logEvent = ((RingBufferLogEvent) logEvent).createMemento();
143        }
144        logEvent.getMessage().getFormattedMessage(); // LOG4J2-763: ask message to freeze parameters
145        final Log4jLogEvent coreEvent = (Log4jLogEvent) logEvent;
146        boolean appendSuccessful = false;
147        if (blocking) {
148            if (isAppenderThread.get() == Boolean.TRUE && queue.remainingCapacity() == 0) {
149                // LOG4J2-485: avoid deadlock that would result from trying
150                // to add to a full queue from appender thread
151                coreEvent.setEndOfBatch(false); // queue is definitely not empty!
152                appendSuccessful = thread.callAppenders(coreEvent);
153            } else {
154                final Serializable serialized = Log4jLogEvent.serialize(coreEvent, includeLocation);
155                try {
156                    // wait for free slots in the queue
157                    queue.put(serialized);
158                    appendSuccessful = true;
159                } catch (final InterruptedException e) {
160                    // LOG4J2-1049: Some applications use Thread.interrupt() to send
161                    // messages between application threads. This does not necessarily
162                    // mean that the queue is full. To prevent dropping a log message,
163                    // quickly try to offer the event to the queue again.
164                    // (Yes, this means there is a possibility the same event is logged twice.)
165                    //
166                    // Finally, catching the InterruptedException means the
167                    // interrupted flag has been cleared on the current thread.
168                    // This may interfere with the application's expectation of
169                    // being interrupted, so when we are done, we set the interrupted
170                    // flag again.
171                    appendSuccessful = queue.offer(serialized);
172                    if (!appendSuccessful) {
173                        LOGGER.warn("Interrupted while waiting for a free slot in the AsyncAppender LogEvent-queue {}",
174                        getName());
175                    }
176                    // set the interrupted flag again.
177                    Thread.currentThread().interrupt();
178                }
179            }
180        } else {
181            appendSuccessful = queue.offer(Log4jLogEvent.serialize(coreEvent, includeLocation));
182            if (!appendSuccessful) {
183                error("Appender " + getName() + " is unable to write primary appenders. queue is full");
184            }
185        }
186        if (!appendSuccessful && errorAppender != null) {
187            errorAppender.callAppender(coreEvent);
188        }
189    }
190
191    /**
192     * Create an AsyncAppender.
193     * @param appenderRefs The Appenders to reference.
194     * @param errorRef An optional Appender to write to if the queue is full or other errors occur.
195     * @param blocking True if the Appender should wait when the queue is full. The default is true.
196     * @param size The size of the event queue. The default is 128.
197     * @param name The name of the Appender.
198     * @param includeLocation whether to include location information. The default is false.
199     * @param filter The Filter or null.
200     * @param config The Configuration.
201     * @param ignoreExceptions If {@code "true"} (default) exceptions encountered when appending events are logged;
202     *                         otherwise they are propagated to the caller.
203     * @return The AsyncAppender.
204     */
205    @PluginFactory
206    public static AsyncAppender createAppender(@PluginElement("AppenderRef") final AppenderRef[] appenderRefs,
207            @PluginAttribute("errorRef") @PluginAliases("error-ref") final String errorRef,
208            @PluginAttribute(value = "blocking", defaultBoolean = true) final boolean blocking,
209            @PluginAttribute(value = "bufferSize", defaultInt = DEFAULT_QUEUE_SIZE) final int size,
210            @PluginAttribute("name") final String name,
211            @PluginAttribute(value = "includeLocation", defaultBoolean = false) final boolean includeLocation,
212            @PluginElement("Filter") final Filter filter,
213            @PluginConfiguration final Configuration config,
214            @PluginAttribute(value = "ignoreExceptions", defaultBoolean = true) final boolean ignoreExceptions) {
215        if (name == null) {
216            LOGGER.error("No name provided for AsyncAppender");
217            return null;
218        }
219        if (appenderRefs == null) {
220            LOGGER.error("No appender references provided to AsyncAppender {}", name);
221        }
222
223        return new AsyncAppender(name, filter, appenderRefs, errorRef,
224                size, blocking, ignoreExceptions, config, includeLocation);
225    }
226
227    /**
228     * Thread that calls the Appenders.
229     */
230    private class AsyncThread extends Thread {
231
232        private volatile boolean shutdown = false;
233        private final List<AppenderControl> appenders;
234        private final BlockingQueue<Serializable> queue;
235
236        public AsyncThread(final List<AppenderControl> appenders, final BlockingQueue<Serializable> queue) {
237            this.appenders = appenders;
238            this.queue = queue;
239            setDaemon(true);
240            setName("AsyncAppenderThread" + threadSequence.getAndIncrement());
241        }
242
243        @Override
244        public void run() {
245            isAppenderThread.set(Boolean.TRUE); // LOG4J2-485
246            while (!shutdown) {
247                Serializable s;
248                try {
249                    s = queue.take();
250                    if (s != null && s instanceof String && SHUTDOWN.equals(s.toString())) {
251                        shutdown = true;
252                        continue;
253                    }
254                } catch (final InterruptedException ex) {
255                    break; // LOG4J2-830
256                }
257                final Log4jLogEvent event = Log4jLogEvent.deserialize(s);
258                event.setEndOfBatch(queue.isEmpty());
259                final boolean success = callAppenders(event);
260                if (!success && errorAppender != null) {
261                    try {
262                        errorAppender.callAppender(event);
263                    } catch (final Exception ex) {
264                        // Silently accept the error.
265                    }
266                }
267            }
268            // Process any remaining items in the queue.
269            LOGGER.trace("AsyncAppender.AsyncThread shutting down. Processing remaining {} queue events.",
270                    queue.size());
271            int count= 0;
272            int ignored = 0;
273            while (!queue.isEmpty()) {
274                try {
275                    final Serializable s = queue.take();
276                    if (Log4jLogEvent.canDeserialize(s)) {
277                        final Log4jLogEvent event = Log4jLogEvent.deserialize(s);
278                        event.setEndOfBatch(queue.isEmpty());
279                        callAppenders(event);
280                        count++;
281                    } else {
282                        ignored++;
283                        LOGGER.trace("Ignoring event of class {}", s.getClass().getName());
284                    }
285                } catch (final InterruptedException ex) {
286                    // May have been interrupted to shut down.
287                    // Here we ignore interrupts and try to process all remaining events.
288                }
289            }
290            LOGGER.trace("AsyncAppender.AsyncThread stopped. Queue has {} events remaining. " +
291                        "Processed {} and ignored {} events since shutdown started.",
292                        queue.size(), count, ignored);
293        }
294
295        /**
296         * Calls {@link AppenderControl#callAppender(LogEvent) callAppender} on
297         * all registered {@code AppenderControl} objects, and returns {@code true}
298         * if at least one appender call was successful, {@code false} otherwise.
299         * Any exceptions are silently ignored.
300         *
301         * @param event the event to forward to the registered appenders
302         * @return {@code true} if at least one appender call succeeded, {@code false} otherwise
303         */
304        boolean callAppenders(final Log4jLogEvent event) {
305            boolean success = false;
306            for (final AppenderControl control : appenders) {
307                try {
308                    control.callAppender(event);
309                    success = true;
310                } catch (final Exception ex) {
311                    // If no appender is successful the error appender will get it.
312                }
313            }
314            return success;
315        }
316
317        public void shutdown() {
318            shutdown = true;
319            if (queue.isEmpty()) {
320                queue.offer(SHUTDOWN);
321            }
322        }
323    }
324
325    /**
326     * Returns the names of the appenders that this asyncAppender delegates to
327     * as an array of Strings.
328     * @return the names of the sink appenders
329     */
330    public String[] getAppenderRefStrings() {
331        final String[] result = new String[appenderRefs.length];
332        for (int i = 0; i < result.length; i++) {
333            result[i] = appenderRefs[i].getRef();
334        }
335        return result;
336    }
337
338    /**
339     * Returns {@code true} if this AsyncAppender will take a snapshot of the stack with
340     * every log event to determine the class and method where the logging call
341     * was made.
342     * @return {@code true} if location is included with every event, {@code false} otherwise
343     */
344    public boolean isIncludeLocation() {
345        return includeLocation;
346    }
347
348    /**
349     * Returns {@code true} if this AsyncAppender will block when the queue is full,
350     * or {@code false} if events are dropped when the queue is full.
351     * @return whether this AsyncAppender will block or drop events when the queue is full.
352     */
353    public boolean isBlocking() {
354        return blocking;
355    }
356
357    /**
358     * Returns the name of the appender that any errors are logged to or {@code null}.
359     * @return the name of the appender that any errors are logged to or {@code null}
360     */
361    public String getErrorRef() {
362        return errorRef;
363    }
364
365    public int getQueueCapacity() {
366        return queueSize;
367    }
368
369    public int getQueueRemainingCapacity() {
370        return queue.remainingCapacity();
371    }
372}