1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.logging.log4j.core.appender;
18
19 import java.io.Serializable;
20 import java.util.concurrent.locks.Lock;
21 import java.util.concurrent.locks.ReadWriteLock;
22 import java.util.concurrent.locks.ReentrantReadWriteLock;
23
24 import org.apache.logging.log4j.core.Filter;
25 import org.apache.logging.log4j.core.Layout;
26 import org.apache.logging.log4j.core.LogEvent;
27
28 /**
29 * Appends log events as bytes to a byte output stream. The stream encoding is defined in the layout.
30 */
31 public abstract class AbstractOutputStreamAppender extends AbstractAppender {
32
33 /**
34 * Immediate flush means that the underlying writer or output stream
35 * will be flushed at the end of each append operation. Immediate
36 * flush is slower but ensures that each append request is actually
37 * written. If <code>immediateFlush</code> is set to
38 * {@code false}, then there is a good chance that the last few
39 * logs events are not actually written to persistent media if and
40 * when the application crashes.
41 */
42 protected final boolean immediateFlush;
43
44 private volatile OutputStreamManager manager;
45
46 private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
47 private final Lock readLock = rwLock.readLock();
48 private final Lock writeLock = rwLock.writeLock();
49
50 /**
51 * Instantiate a WriterAppender and set the output destination to a
52 * new {@link java.io.OutputStreamWriter} initialized with <code>os</code>
53 * as its {@link java.io.OutputStream}.
54 * @param name The name of the Appender.
55 * @param layout The layout to format the message.
56 * @param manager The OutputStreamManager.
57 */
58 protected AbstractOutputStreamAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter,
59 final boolean ignoreExceptions, final boolean immediateFlush,
60 final OutputStreamManager manager) {
61 super(name, filter, layout, ignoreExceptions);
62 this.manager = manager;
63 this.immediateFlush = immediateFlush;
64 }
65
66 protected OutputStreamManager getManager() {
67 return manager;
68 }
69
70 protected void replaceManager(final OutputStreamManager newManager) {
71
72 writeLock.lock();
73 try {
74 final OutputStreamManager old = manager;
75 manager = newManager;
76 old.release();
77 } finally {
78 writeLock.unlock();
79 }
80
81 }
82
83 @Override
84 public void start() {
85 if (getLayout() == null) {
86 LOGGER.error("No layout set for the appender named [" + getName() + "].");
87 }
88 if (manager == null) {
89 LOGGER.error("No OutputStreamManager set for the appender named [" + getName() + "].");
90 }
91 super.start();
92 }
93
94 @Override
95 public void stop() {
96 super.stop();
97 manager.release();
98 }
99
100 /**
101 * Actual writing occurs here.
102 * <p/>
103 * <p>Most subclasses of <code>AbstractOutputStreamAppender</code> will need to
104 * override this method.
105 * @param event The LogEvent.
106 */
107 @Override
108 public void append(final LogEvent event) {
109 readLock.lock();
110 try {
111 final byte[] bytes = getLayout().toByteArray(event);
112 if (bytes.length > 0) {
113 manager.write(bytes);
114 if (this.immediateFlush || event.isEndOfBatch()) {
115 manager.flush();
116 }
117 }
118 } catch (final AppenderLoggingException ex) {
119 error("Unable to write to stream " + manager.getName() + " for appender " + getName());
120 throw ex;
121 } finally {
122 readLock.unlock();
123 }
124 }
125 }