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.concurrent.locks.Lock;
021import java.util.concurrent.locks.ReadWriteLock;
022import java.util.concurrent.locks.ReentrantReadWriteLock;
023
024import org.apache.logging.log4j.core.Filter;
025import org.apache.logging.log4j.core.Layout;
026import org.apache.logging.log4j.core.LogEvent;
027
028/**
029 * Appends log events as bytes to a byte output stream. The stream encoding is defined in the layout.
030 * 
031 * @param <M> The kind of {@link OutputStreamManager} under management
032 */
033public abstract class AbstractOutputStreamAppender<M extends OutputStreamManager> extends AbstractAppender {
034
035    private static final long serialVersionUID = 1L;
036
037    /**
038     * Immediate flush means that the underlying writer or output stream
039     * will be flushed at the end of each append operation. Immediate
040     * flush is slower but ensures that each append request is actually
041     * written. If <code>immediateFlush</code> is set to
042     * {@code false}, then there is a good chance that the last few
043     * logs events are not actually written to persistent media if and
044     * when the application crashes.
045     */
046    protected final boolean immediateFlush;
047
048    private final M manager;
049
050    private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
051    private final Lock readLock = rwLock.readLock();
052    
053    /**
054     * Instantiate a WriterAppender and set the output destination to a
055     * new {@link java.io.OutputStreamWriter} initialized with <code>os</code>
056     * as its {@link java.io.OutputStream}.
057     * @param name The name of the Appender.
058     * @param layout The layout to format the message.
059     * @param manager The OutputStreamManager.
060     */
061    protected AbstractOutputStreamAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter,
062                                           final boolean ignoreExceptions, final boolean immediateFlush,
063                                           final M manager) {
064        super(name, filter, layout, ignoreExceptions);
065        this.manager = manager;
066        this.immediateFlush = immediateFlush;
067    }
068
069    /**
070     * Gets the manager.
071     * 
072     * @return the manager.
073     */
074    public M getManager() {
075        return manager;
076    }
077
078    @Override
079    public void start() {
080        if (getLayout() == null) {
081            LOGGER.error("No layout set for the appender named [" + getName() + "].");
082        }
083        if (manager == null) {
084            LOGGER.error("No OutputStreamManager set for the appender named [" + getName() + "].");
085        }
086        super.start();
087    }
088
089    @Override
090    public void stop() {
091        super.stop();
092        manager.release();
093    }
094
095    /**
096     * Actual writing occurs here.
097     * <p>
098     * Most subclasses of <code>AbstractOutputStreamAppender</code> will need to override this method.
099     * </p>
100     * 
101     * @param event
102     *        The LogEvent.
103     */
104    @Override
105    public void append(final LogEvent event) {
106        readLock.lock();
107        try {
108            final byte[] bytes = getLayout().toByteArray(event);
109            if (bytes.length > 0) {
110                manager.write(bytes);
111                if (this.immediateFlush || event.isEndOfBatch()) {
112                    manager.flush();
113                }
114            }
115        } catch (final AppenderLoggingException ex) {
116            error("Unable to write to stream " + manager.getName() + " for appender " + getName());
117            throw ex;
118        } finally {
119            readLock.unlock();
120        }
121    }
122}