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.impl;
018
019import java.util.List;
020
021import org.apache.logging.log4j.Level;
022import org.apache.logging.log4j.Marker;
023import org.apache.logging.log4j.ThreadContext;
024import org.apache.logging.log4j.core.ContextDataInjector;
025import org.apache.logging.log4j.core.LogEvent;
026import org.apache.logging.log4j.core.async.ThreadNameCachingStrategy;
027import org.apache.logging.log4j.core.config.Property;
028import org.apache.logging.log4j.core.util.Clock;
029import org.apache.logging.log4j.core.util.ClockFactory;
030import org.apache.logging.log4j.message.Message;
031import org.apache.logging.log4j.util.StringMap;
032
033/**
034 * Garbage-free LogEventFactory that reuses a single mutable log event.
035 * @since 2.6
036 */
037public class ReusableLogEventFactory implements LogEventFactory {
038    private static final ThreadNameCachingStrategy THREAD_NAME_CACHING_STRATEGY = ThreadNameCachingStrategy.create();
039    private static final Clock CLOCK = ClockFactory.getClock();
040
041    private static ThreadLocal<MutableLogEvent> mutableLogEventThreadLocal = new ThreadLocal<>();
042    private final ContextDataInjector injector = ContextDataInjectorFactory.createInjector();
043
044    /**
045     * Creates a log event.
046     *
047     * @param loggerName The name of the Logger.
048     * @param marker An optional Marker.
049     * @param fqcn The fully qualified class name of the caller.
050     * @param level The event Level.
051     * @param message The Message.
052     * @param properties Properties to be added to the log event.
053     * @param t An optional Throwable.
054     * @return The LogEvent.
055     */
056    @Override
057    public LogEvent createEvent(final String loggerName, final Marker marker,
058                                final String fqcn, final Level level, final Message message,
059                                final List<Property> properties, final Throwable t) {
060        MutableLogEvent result = mutableLogEventThreadLocal.get();
061        if (result == null || result.reserved) {
062            final boolean initThreadLocal = result == null;
063            result = new MutableLogEvent();
064
065            // usually no need to re-initialize thread-specific fields since the event is stored in a ThreadLocal
066            result.setThreadId(Thread.currentThread().getId());
067            result.setThreadName(Thread.currentThread().getName()); // Thread.getName() allocates Objects on each call
068            result.setThreadPriority(Thread.currentThread().getPriority());
069            if (initThreadLocal) {
070                mutableLogEventThreadLocal.set(result);
071            }
072        }
073        result.reserved = true;
074        result.clear(); // ensure any previously cached values (thrownProxy, source, etc.) are cleared
075
076        result.setLoggerName(loggerName);
077        result.setMarker(marker);
078        result.setLoggerFqcn(fqcn);
079        result.setLevel(level == null ? Level.OFF : level);
080        result.setMessage(message);
081        result.initTime(CLOCK, Log4jLogEvent.getNanoClock());
082        result.setThrown(t);
083        result.setContextData(injector.injectContextData(properties, (StringMap) result.getContextData()));
084        result.setContextStack(ThreadContext.getDepth() == 0 ? ThreadContext.EMPTY_STACK : ThreadContext.cloneStack());// mutable copy
085
086        if (THREAD_NAME_CACHING_STRATEGY == ThreadNameCachingStrategy.UNCACHED) {
087            result.setThreadName(Thread.currentThread().getName()); // Thread.getName() allocates Objects on each call
088            result.setThreadPriority(Thread.currentThread().getPriority());
089        }
090        return result;
091    }
092
093    /**
094     * Switches the {@code reserved} flag off if the specified event is a MutableLogEvent, otherwise does nothing.
095     * This flag is used internally to verify that a reusable log event is no longer in use and can be reused.
096     * @param logEvent the log event to make available again
097     * @since 2.7
098     */
099    public static void release(final LogEvent logEvent) { // LOG4J2-1583
100        if (logEvent instanceof MutableLogEvent) {
101            final MutableLogEvent mutableLogEvent = (MutableLogEvent) logEvent;
102            mutableLogEvent.clear();
103            mutableLogEvent.reserved = false;
104        }
105    }
106}