Apache Log4j Core Implementation provides the functional components of the logging system. Users are free to create their own plugins and include them in the logging configuration. Apache Log4j Core is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j Core Implementation is provided in a separate JAR file like log4j-core-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 2.14.1 below.

⏎ org/apache/logging/log4j/core/config/AwaitCompletionReliabilityStrategy.java

/*
 * 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.
 */

package org.apache.logging.log4j.core.config;

import java.util.Objects;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.message.Message;
import org.apache.logging.log4j.util.Supplier;

/**
 * ReliabilityStrategy that counts the number of threads that have started to log an event but have not completed yet,
 * and waits for these threads to finish before allowing the appenders to be stopped.
 */
public class AwaitCompletionReliabilityStrategy implements ReliabilityStrategy, LocationAwareReliabilityStrategy {
    private static final int MAX_RETRIES = 3;
    private final AtomicInteger counter = new AtomicInteger();
    private final AtomicBoolean shutdown = new AtomicBoolean(false);
    private final Lock shutdownLock = new ReentrantLock();
    private final Condition noLogEvents = shutdownLock.newCondition(); // should only be used when shutdown == true
    private final LoggerConfig loggerConfig;

    public AwaitCompletionReliabilityStrategy(final LoggerConfig loggerConfig) {
        this.loggerConfig = Objects.requireNonNull(loggerConfig, "loggerConfig is null");
    }

    /*
     * (non-Javadoc)
     *
     * @see org.apache.logging.log4j.core.config.ReliabilityStrategy#log(org.apache.logging.log4j.util.Supplier,
     * java.lang.String, java.lang.String, org.apache.logging.log4j.Marker, org.apache.logging.log4j.Level,
     * org.apache.logging.log4j.message.Message, java.lang.Throwable)
     */
    @Override
    public void log(final Supplier<LoggerConfig> reconfigured, final String loggerName, final String fqcn,
            final Marker marker, final Level level, final Message data, final Throwable t) {

        final LoggerConfig config = getActiveLoggerConfig(reconfigured);
        try {
            config.log(loggerName, fqcn, marker, level, data, t);
        } finally {
            config.getReliabilityStrategy().afterLogEvent();
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see org.apache.logging.log4j.core.config.ReliabilityStrategy#log(org.apache.logging.log4j.util.Supplier,
     * java.lang.String, java.lang.String, java.lang.StackTraceElement, org.apache.logging.log4j.Marker,
     * org.apache.logging.log4j.Level, org.apache.logging.log4j.message.Message, java.lang.Throwable)
     */
    @Override
    public void log(final Supplier<LoggerConfig> reconfigured, final String loggerName, final String fqcn,
        final StackTraceElement location, final Marker marker, final Level level, final Message data,
        final Throwable t) {
        final LoggerConfig config = getActiveLoggerConfig(reconfigured);
        try {
            config.log(loggerName, fqcn, location, marker, level, data, t);
        } finally {
            config.getReliabilityStrategy().afterLogEvent();
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see org.apache.logging.log4j.core.config.ReliabilityStrategy#log(org.apache.logging.log4j.util.Supplier,
     * org.apache.logging.log4j.core.LogEvent)
     */
    @Override
    public void log(final Supplier<LoggerConfig> reconfigured, final LogEvent event) {
        final LoggerConfig config = getActiveLoggerConfig(reconfigured);
        try {
            config.log(event);
        } finally {
            config.getReliabilityStrategy().afterLogEvent();
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.apache.logging.log4j.core.config.ReliabilityStrategy#beforeLogEvent(org.apache.logging.log4j.core.config.
     * LoggerConfig, org.apache.logging.log4j.util.Supplier)
     */
    @Override
    public LoggerConfig getActiveLoggerConfig(final Supplier<LoggerConfig> next) {
        LoggerConfig result = this.loggerConfig;
        if (!beforeLogEvent()) {
            result = next.get();
            return result == this.loggerConfig ? result : result.getReliabilityStrategy().getActiveLoggerConfig(next);
        }
        return result;
    }

    private boolean beforeLogEvent() {
        return counter.incrementAndGet() > 0;
    }

    @Override
    public void afterLogEvent() {
        if (counter.decrementAndGet() == 0 && shutdown.get()) {
            signalCompletionIfShutdown();
        }
    }

    private void signalCompletionIfShutdown() {
        final Lock lock = shutdownLock;
        lock.lock();
        try {
            noLogEvents.signalAll();
        } finally {
            lock.unlock();
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see org.apache.logging.log4j.core.config.ReliabilityStrategy#beforeStopAppenders()
     */
    @Override
    public void beforeStopAppenders() {
        waitForCompletion();
    }

    /**
     * Waits for all log events to complete before returning.
     */
    private void waitForCompletion() {
        shutdownLock.lock();
        try {
            if (shutdown.compareAndSet(false, true)) {
                int retries = 0;
                // repeat while counter is non-zero
                while (!counter.compareAndSet(0, Integer.MIN_VALUE)) {

                    // counter was non-zero
                    if (counter.get() < 0) { // this should not happen
                        return; // but if it does, we are already done
                    }
                    // counter greater than zero, wait for afterLogEvent to decrease count
                    try {
                        noLogEvents.await(retries + 1, TimeUnit.SECONDS);
                    } catch (final InterruptedException ie) {
                        if (++retries > MAX_RETRIES) {
                            break;
                        }
                    }
                }
            }
        } finally {
            shutdownLock.unlock();
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.apache.logging.log4j.core.config.ReliabilityStrategy#beforeStopConfiguration(org.apache.logging.log4j.core
     * .config.Configuration)
     */
    @Override
    public void beforeStopConfiguration(final Configuration configuration) {
        // no action
    }

}

⏎ org/apache/logging/log4j/core/config/AwaitCompletionReliabilityStrategy.java

Or download all of them as a single archive file:

File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06
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