    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        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    }