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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  package org.apache.logging.log4j.core.async;
18  
19  import java.util.Map;
20  
21  import org.apache.logging.log4j.Level;
22  import org.apache.logging.log4j.Marker;
23  import org.apache.logging.log4j.ThreadContext;
24  import org.apache.logging.log4j.ThreadContext.ContextStack;
25  import org.apache.logging.log4j.core.Logger;
26  import org.apache.logging.log4j.core.LoggerContext;
27  import org.apache.logging.log4j.core.config.Configuration;
28  import org.apache.logging.log4j.core.config.Property;
29  import org.apache.logging.log4j.core.config.ReliabilityStrategy;
30  import org.apache.logging.log4j.core.impl.Log4jLogEvent;
31  import org.apache.logging.log4j.core.util.Clock;
32  import org.apache.logging.log4j.core.util.ClockFactory;
33  import org.apache.logging.log4j.core.util.Constants;
34  import org.apache.logging.log4j.core.util.NanoClock;
35  import org.apache.logging.log4j.message.Message;
36  import org.apache.logging.log4j.message.MessageFactory;
37  import org.apache.logging.log4j.message.ReusableMessage;
38  import org.apache.logging.log4j.status.StatusLogger;
39  
40  import com.lmax.disruptor.EventTranslatorVararg;
41  import com.lmax.disruptor.dsl.Disruptor;
42  
43  /**
44   * AsyncLogger is a logger designed for high throughput and low latency logging. It does not perform any I/O in the
45   * calling (application) thread, but instead hands off the work to another thread as soon as possible. The actual
46   * logging is performed in the background thread. It uses the LMAX Disruptor library for inter-thread communication. (<a
47   * href="http://lmax-exchange.github.com/disruptor/" >http://lmax-exchange.github.com/disruptor/</a>)
48   * <p>
49   * To use AsyncLogger, specify the System property
50   * {@code -DLog4jContextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector} before you obtain a
51   * Logger, and all Loggers returned by LogManager.getLogger will be AsyncLoggers.
52   * <p>
53   * Note that for performance reasons, this logger does not include source location by default. You need to specify
54   * {@code includeLocation="true"} in the configuration or any %class, %location or %line conversion patterns in your
55   * log4j.xml configuration will produce either a "?" character or no output at all.
56   * <p>
57   * For best performance, use AsyncLogger with the RandomAccessFileAppender or RollingRandomAccessFileAppender, with
58   * immediateFlush=false. These appenders have built-in support for the batching mechanism used by the Disruptor library,
59   * and they will flush to disk at the end of each batch. This means that even with immediateFlush=false, there will
60   * never be any items left in the buffer; all log events will all be written to disk in a very efficient manner.
61   */
62  public class AsyncLogger extends Logger implements EventTranslatorVararg<RingBufferLogEvent> {
63      // Implementation note: many methods in this class are tuned for performance. MODIFY WITH CARE!
64      // Specifically, try to keep the hot methods to 35 bytecodes or less:
65      // this is within the MaxInlineSize threshold and makes these methods candidates for
66      // immediate inlining instead of waiting until they are designated "hot enough".
67  
68      private static final StatusLogger LOGGER = StatusLogger.getLogger();
69      private static final Clock CLOCK = ClockFactory.getClock(); // not reconfigurable
70  
71      private static final ThreadNameCachingStrategy THREAD_NAME_CACHING_STRATEGY = ThreadNameCachingStrategy.create();
72  
73      private final ThreadLocal<RingBufferLogEventTranslator> threadLocalTranslator = new ThreadLocal<>();
74      private final AsyncLoggerDisruptor loggerDisruptor;
75  
76      private volatile boolean includeLocation; // reconfigurable
77      private volatile NanoClock nanoClock; // reconfigurable
78  
79      /**
80       * Constructs an {@code AsyncLogger} with the specified context, name and message factory.
81       *
82       * @param context context of this logger
83       * @param name name of this logger
84       * @param messageFactory message factory of this logger
85       * @param loggerDisruptor helper class that logging can be delegated to. This object owns the Disruptor.
86       */
87      public AsyncLogger(final LoggerContext context, final String name, final MessageFactory messageFactory,
88              final AsyncLoggerDisruptor loggerDisruptor) {
89          super(context, name, messageFactory);
90          this.loggerDisruptor = loggerDisruptor;
91          includeLocation = privateConfig.loggerConfig.isIncludeLocation();
92          nanoClock = context.getConfiguration().getNanoClock();
93      }
94  
95      /*
96       * (non-Javadoc)
97       *
98       * @see org.apache.logging.log4j.core.Logger#updateConfiguration(org.apache.logging.log4j.core.config.Configuration)
99       */
100     @Override
101     protected void updateConfiguration(final Configuration newConfig) {
102         nanoClock = newConfig.getNanoClock();
103         includeLocation = newConfig.getLoggerConfig(name).isIncludeLocation();
104         super.updateConfiguration(newConfig);
105     }
106 
107     // package protected for unit tests
108     NanoClock getNanoClock() {
109         return nanoClock;
110     }
111 
112     private RingBufferLogEventTranslator getCachedTranslator() {
113         RingBufferLogEventTranslator result = threadLocalTranslator.get();
114         if (result == null) {
115             result = new RingBufferLogEventTranslator();
116             threadLocalTranslator.set(result);
117         }
118         return result;
119     }
120 
121     @Override
122     public void logMessage(final String fqcn, final Level level, final Marker marker, final Message message,
123             final Throwable thrown) {
124 
125         if (loggerDisruptor.isUseThreadLocals()) {
126             logWithThreadLocalTranslator(fqcn, level, marker, message, thrown);
127         } else {
128             // LOG4J2-1172: avoid storing non-JDK classes in ThreadLocals to avoid memory leaks in web apps
129             logWithVarargTranslator(fqcn, level, marker, message, thrown);
130         }
131     }
132 
133     private boolean isReused(final Message message) {
134         return message instanceof ReusableMessage;
135     }
136 
137     /**
138      * Enqueues the specified log event data for logging in a background thread.
139      * <p>
140      * This re-uses a {@code RingBufferLogEventTranslator} instance cached in a {@code ThreadLocal} to avoid creating
141      * unnecessary objects with each event.
142      *
143      * @param fqcn fully qualified name of the caller
144      * @param level level at which the caller wants to log the message
145      * @param marker message marker
146      * @param message the log message
147      * @param thrown a {@code Throwable} or {@code null}
148      */
149     private void logWithThreadLocalTranslator(final String fqcn, final Level level, final Marker marker,
150             final Message message, final Throwable thrown) {
151         // Implementation note: this method is tuned for performance. MODIFY WITH CARE!
152 
153         final RingBufferLogEventTranslator translator = getCachedTranslator();
154         initTranslator(translator, fqcn, level, marker, message, thrown);
155         initTranslatorThreadValues(translator);
156         publish(translator);
157     }
158 
159     private void publish(final RingBufferLogEventTranslator translator) {
160         if (!loggerDisruptor.tryPublish(translator)) {
161             handleRingBufferFull(translator);
162         }
163     }
164 
165     private void handleRingBufferFull(final RingBufferLogEventTranslator translator) {
166         final EventRoute eventRoute = loggerDisruptor.getEventRoute(translator.level);
167         switch (eventRoute) {
168             case ENQUEUE:
169                 loggerDisruptor.enqueueLogMessageInfo(translator);
170                 break;
171             case SYNCHRONOUS:
172                 logMessageInCurrentThread(translator.fqcn, translator.level, translator.marker, translator.message,
173                         translator.thrown);
174                 break;
175             case DISCARD:
176                 break;
177             default:
178                 throw new IllegalStateException("Unknown EventRoute " + eventRoute);
179         }
180     }
181 
182     private void initTranslator(final RingBufferLogEventTranslator translator, final String fqcn,
183             final Level level, final Marker marker, final Message message, final Throwable thrown) {
184 
185         translator.setBasicValues(this, name, marker, fqcn, level, message, //
186                 // don't construct ThrowableProxy until required
187                 thrown,
188 
189                 // config properties are taken care of in the EventHandler thread
190                 // in the AsyncLogger#actualAsyncLog method
191 
192                 // needs shallow copy to be fast (LOG4J2-154)
193                 ThreadContext.getImmutableContext(), //
194 
195                 // needs shallow copy to be fast (LOG4J2-154)
196                 ThreadContext.getImmutableStack(), //
197                 // location (expensive to calculate)
198                 calcLocationIfRequested(fqcn), //
199                 CLOCK.currentTimeMillis(), //
200                 nanoClock.nanoTime() //
201         );
202     }
203 
204     private void initTranslatorThreadValues(final RingBufferLogEventTranslator translator) {
205         // constant check should be optimized out when using default (CACHED)
206         if (THREAD_NAME_CACHING_STRATEGY == ThreadNameCachingStrategy.UNCACHED) {
207             translator.updateThreadValues();
208         }
209     }
210 
211     /**
212      * Returns the caller location if requested, {@code null} otherwise.
213      *
214      * @param fqcn fully qualified caller name.
215      * @return the caller location if requested, {@code null} otherwise.
216      */
217     private StackTraceElement calcLocationIfRequested(final String fqcn) {
218         // location: very expensive operation. LOG4J2-153:
219         // Only include if "includeLocation=true" is specified,
220         // exclude if not specified or if "false" was specified.
221         return includeLocation ? Log4jLogEvent.calcLocation(fqcn) : null;
222     }
223 
224     /**
225      * Enqueues the specified log event data for logging in a background thread.
226      * <p>
227      * This creates a new varargs Object array for each invocation, but does not store any non-JDK classes in a
228      * {@code ThreadLocal} to avoid memory leaks in web applications (see LOG4J2-1172).
229      *
230      * @param fqcn fully qualified name of the caller
231      * @param level level at which the caller wants to log the message
232      * @param marker message marker
233      * @param message the log message
234      * @param thrown a {@code Throwable} or {@code null}
235      */
236     private void logWithVarargTranslator(final String fqcn, final Level level, final Marker marker,
237             final Message message, final Throwable thrown) {
238         // Implementation note: candidate for optimization: exceeds 35 bytecodes.
239 
240         final Disruptor<RingBufferLogEvent> disruptor = loggerDisruptor.getDisruptor();
241         if (disruptor == null) {
242             LOGGER.error("Ignoring log event after Log4j has been shut down.");
243             return;
244         }
245         // if the Message instance is reused, there is no point in freezing its message here
246         if (!Constants.FORMAT_MESSAGES_IN_BACKGROUND && !isReused(message)) { // LOG4J2-898: user may choose
247             message.getFormattedMessage(); // LOG4J2-763: ask message to freeze parameters
248         }
249         // calls the translateTo method on this AsyncLogger
250         disruptor.getRingBuffer().publishEvent(this, this, calcLocationIfRequested(fqcn), fqcn, level, marker, message,
251                 thrown);
252     }
253 
254     /*
255      * (non-Javadoc)
256      *
257      * @see com.lmax.disruptor.EventTranslatorVararg#translateTo(java.lang.Object, long, java.lang.Object[])
258      */
259     @Override
260     public void translateTo(final RingBufferLogEvent event, final long sequence, final Object... args) {
261         // Implementation note: candidate for optimization: exceeds 35 bytecodes.
262         final AsyncLogger asyncLogger = (AsyncLogger) args[0];
263         final StackTraceElement location = (StackTraceElement) args[1];
264         final String fqcn = (String) args[2];
265         final Level level = (Level) args[3];
266         final Marker marker = (Marker) args[4];
267         final Message message = (Message) args[5];
268         final Throwable thrown = (Throwable) args[6];
269 
270         // needs shallow copy to be fast (LOG4J2-154)
271         final Map<String, String> contextMap = ThreadContext.getImmutableContext();
272 
273         // needs shallow copy to be fast (LOG4J2-154)
274         final ContextStack contextStack = ThreadContext.getImmutableStack();
275 
276         final Thread currentThread = Thread.currentThread();
277         final String threadName = THREAD_NAME_CACHING_STRATEGY.getThreadName();
278         event.setValues(asyncLogger, asyncLogger.getName(), marker, fqcn, level, message, thrown, contextMap,
279                 contextStack, currentThread.getId(), threadName, currentThread.getPriority(), location,
280                 CLOCK.currentTimeMillis(), nanoClock.nanoTime());
281     }
282 
283     /**
284      * LOG4J2-471: prevent deadlock when RingBuffer is full and object being logged calls Logger.log() from its
285      * toString() method
286      *
287      * @param fqcn fully qualified caller name
288      * @param level log level
289      * @param marker optional marker
290      * @param message log message
291      * @param thrown optional exception
292      */
293     void logMessageInCurrentThread(final String fqcn, final Level level, final Marker marker,
294             final Message message, final Throwable thrown) {
295         // bypass RingBuffer and invoke Appender directly
296         final ReliabilityStrategy strategy = privateConfig.loggerConfig.getReliabilityStrategy();
297         strategy.log(this, getName(), fqcn, marker, level, message, thrown);
298     }
299 
300     /**
301      * This method is called by the EventHandler that processes the RingBufferLogEvent in a separate thread.
302      *
303      * @param event the event to log
304      */
305     public void actualAsyncLog(final RingBufferLogEvent event) {
306         final Map<Property, Boolean> properties = privateConfig.loggerConfig.getProperties();
307         event.mergePropertiesIntoContextMap(properties, privateConfig.config.getStrSubstitutor());
308         final ReliabilityStrategy strategy = privateConfig.loggerConfig.getReliabilityStrategy();
309         strategy.log(this, event);
310     }
311 }