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     */
017    package org.apache.logging.log4j.core.appender;
018    
019    import java.io.Serializable;
020    import java.util.concurrent.locks.Lock;
021    import java.util.concurrent.locks.ReadWriteLock;
022    import java.util.concurrent.locks.ReentrantReadWriteLock;
023    
024    import org.apache.logging.log4j.core.Filter;
025    import org.apache.logging.log4j.core.Layout;
026    import 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     */
033    public abstract class AbstractOutputStreamAppender<M extends OutputStreamManager> extends AbstractAppender {
034    
035        /**
036         * Immediate flush means that the underlying writer or output stream
037         * will be flushed at the end of each append operation. Immediate
038         * flush is slower but ensures that each append request is actually
039         * written. If <code>immediateFlush</code> is set to
040         * {@code false}, then there is a good chance that the last few
041         * logs events are not actually written to persistent media if and
042         * when the application crashes.
043         */
044        protected final boolean immediateFlush;
045    
046        private final M manager;
047    
048        private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
049        private final Lock readLock = rwLock.readLock();
050        
051        /**
052         * Instantiate a WriterAppender and set the output destination to a
053         * new {@link java.io.OutputStreamWriter} initialized with <code>os</code>
054         * as its {@link java.io.OutputStream}.
055         * @param name The name of the Appender.
056         * @param layout The layout to format the message.
057         * @param manager The OutputStreamManager.
058         */
059        protected AbstractOutputStreamAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter,
060                                               final boolean ignoreExceptions, final boolean immediateFlush,
061                                               final M manager) {
062            super(name, filter, layout, ignoreExceptions);
063            this.manager = manager;
064            this.immediateFlush = immediateFlush;
065        }
066    
067        /**
068         * Gets the manager.
069         * 
070         * @return the manager.
071         */
072        public M getManager() {
073            return manager;
074        }
075    
076        @Override
077        public void start() {
078            if (getLayout() == null) {
079                LOGGER.error("No layout set for the appender named [" + getName() + "].");
080            }
081            if (manager == null) {
082                LOGGER.error("No OutputStreamManager set for the appender named [" + getName() + "].");
083            }
084            super.start();
085        }
086    
087        @Override
088        public void stop() {
089            super.stop();
090            manager.release();
091        }
092    
093        /**
094         * Actual writing occurs here.
095         * <p/>
096         * <p>Most subclasses of <code>AbstractOutputStreamAppender</code> will need to
097         * override this method.
098         * @param event The LogEvent.
099         */
100        @Override
101        public void append(final LogEvent event) {
102            readLock.lock();
103            try {
104                final byte[] bytes = getLayout().toByteArray(event);
105                if (bytes.length > 0) {
106                    manager.write(bytes);
107                    if (this.immediateFlush || event.isEndOfBatch()) {
108                        manager.flush();
109                    }
110                }
111            } catch (final AppenderLoggingException ex) {
112                error("Unable to write to stream " + manager.getName() + " for appender " + getName());
113                throw ex;
114            } finally {
115                readLock.unlock();
116            }
117        }
118    }