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/appender/AsyncAppenderEventDispatcher.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.appender;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.AppenderControl;
import org.apache.logging.log4j.core.impl.Log4jLogEvent;
import org.apache.logging.log4j.core.util.Log4jThread;
import org.apache.logging.log4j.status.StatusLogger;

import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;

class AsyncAppenderEventDispatcher extends Log4jThread {

    private static final LogEvent STOP_EVENT = new Log4jLogEvent();

    private static final AtomicLong THREAD_COUNTER = new AtomicLong(0);

    private static final Logger LOGGER = StatusLogger.getLogger();

    private final AppenderControl errorAppender;

    private final List<AppenderControl> appenders;

    private final BlockingQueue<LogEvent> queue;

    private final AtomicBoolean stoppedRef;

    AsyncAppenderEventDispatcher(
            final String name,
            final AppenderControl errorAppender,
            final List<AppenderControl> appenders,
            final BlockingQueue<LogEvent> queue) {
        super("AsyncAppenderEventDispatcher-" + THREAD_COUNTER.incrementAndGet() + "-" + name);
        this.errorAppender = errorAppender;
        this.appenders = appenders;
        this.queue = queue;
        this.stoppedRef = new AtomicBoolean(false);
    }

    @Override
    public void run() {
        LOGGER.trace("{} has started.", getName());
        dispatchAll();
        dispatchRemaining();
    }

    private void dispatchAll() {
        while (!stoppedRef.get()) {
            LogEvent event;
            try {
                event = queue.take();
            } catch (final InterruptedException ignored) {
                // Restore the interrupted flag cleared when the exception is caught.
                interrupt();
                break;
            }
            if (event == STOP_EVENT) {
                break;
            }
            event.setEndOfBatch(queue.isEmpty());
            dispatch(event);
        }
        LOGGER.trace("{} has stopped.", getName());
    }

    private void dispatchRemaining() {
        int eventCount = 0;
        while (true) {
            // Note the non-blocking Queue#poll() method!
            final LogEvent event = queue.poll();
            if (event == null) {
                break;
            }
            // Allow events that managed to be submitted after the sentinel.
            if (event == STOP_EVENT) {
                continue;
            }
            event.setEndOfBatch(queue.isEmpty());
            dispatch(event);
            eventCount++;
        }
        LOGGER.trace(
                "{} has processed the last {} remaining event(s).",
                getName(), eventCount);
    }

    /**
     * Dispatches the given {@code event} to the registered appenders <b>in the
     * current thread</b>.
     */
    void dispatch(final LogEvent event) {

        // Dispatch the event to all registered appenders.
        boolean succeeded = false;
        // noinspection ForLoopReplaceableByForEach (avoid iterator instantion)
        for (int appenderIndex = 0; appenderIndex < appenders.size(); appenderIndex++) {
            final AppenderControl control = appenders.get(appenderIndex);
            try {
                control.callAppender(event);
                succeeded = true;
            } catch (final Throwable error) {
                // If no appender is successful, the error appender will get it.
                // It is okay to simply log it here.
                LOGGER.trace(
                        "{} has failed to call appender {}",
                        getName(), control.getAppenderName(), error);
            }
        }

        // Fallback to the error appender if none has succeeded so far.
        if (!succeeded && errorAppender != null) {
            try {
                errorAppender.callAppender(event);
            } catch (final Throwable error) {
                // If the error appender also fails, there is nothing further
                // we can do about it.
                LOGGER.trace(
                        "{} has failed to call the error appender {}",
                        getName(), errorAppender.getAppenderName(), error);
            }
        }

    }

    void stop(final long timeoutMillis) throws InterruptedException {

        // Mark the completion, if necessary.
        final boolean stopped = stoppedRef.compareAndSet(false, true);
        if (stopped) {
            LOGGER.trace("{} is signaled to stop.", getName());
        }

        // There is a slight chance that the thread is not started yet, wait for
        // it to run. Otherwise, interrupt+join might block.
        // noinspection StatementWithEmptyBody
        while (Thread.State.NEW.equals(getState()));

        // Enqueue the stop event, if there is sufficient room; otherwise,
        // fallback to interruption. (We should avoid interrupting the thread if
        // at all possible due to the subtleties of Java interruption, which
        // will actually close sockets if any blocking operations are in
        // progress! This means a socket appender may surprisingly fail to
        // deliver final events. I recall some oddities with file I/O as well.
        // — ckozak)
        final boolean added = queue.offer(STOP_EVENT);
        if (!added) {
            interrupt();
        }

        // Wait for the completion.
        join(timeoutMillis);

    }

}

⏎ org/apache/logging/log4j/core/appender/AsyncAppenderEventDispatcher.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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