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.db;
18
19 import java.util.concurrent.locks.Lock;
20 import java.util.concurrent.locks.ReadWriteLock;
21 import java.util.concurrent.locks.ReentrantReadWriteLock;
22
23 import org.apache.logging.log4j.LoggingException;
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 import org.apache.logging.log4j.core.appender.AbstractAppender;
28 import org.apache.logging.log4j.core.appender.AppenderLoggingException;
29
30 /**
31 * An abstract Appender for writing events to a database of some type, be it relational or NoSQL. All database appenders
32 * should inherit from this base appender. Three implementations are currently provided:
33 * {@link org.apache.logging.log4j.core.appender.db.jdbc JDBC}, {@link org.apache.logging.log4j.core.appender.db.jpa
34 * JPA}, and <a href="/log4j/2.x/log4j-nosql/apidocs/">NoSQL</a>.
35 *
36 * @param <T> Specifies which type of {@link AbstractDatabaseManager} this Appender requires.
37 */
38 public abstract class AbstractDatabaseAppender<T extends AbstractDatabaseManager> extends AbstractAppender {
39
40 private final ReadWriteLock lock = new ReentrantReadWriteLock();
41 private final Lock readLock = lock.readLock();
42 private final Lock writeLock = lock.writeLock();
43
44 private T manager;
45
46 /**
47 * Instantiates the base appender.
48 *
49 * @param name The appender name.
50 * @param filter The filter, if any, to use.
51 * @param ignoreExceptions If {@code true} exceptions encountered when appending events are logged; otherwise
52 * they are propagated to the caller.
53 * @param manager The matching {@link AbstractDatabaseManager} implementation.
54 */
55 protected AbstractDatabaseAppender(final String name, final Filter filter, final boolean ignoreExceptions,
56 final T manager) {
57 super(name, filter, null, ignoreExceptions);
58 this.manager = manager;
59 }
60
61 /**
62 * This always returns {@code null}, as database appenders do not use a single layout. The JPA and NoSQL appenders
63 * do not use a layout at all. The JDBC appender has a layout-per-column pattern.
64 *
65 * @return {@code null}.
66 */
67 @Override
68 public final Layout<LogEvent> getLayout() {
69 return null;
70 }
71
72 /**
73 * Returns the underlying manager in use within this appender.
74 *
75 * @return the manager.
76 */
77 public final T getManager() {
78 return this.manager;
79 }
80
81 @Override
82 public final void start() {
83 if (this.getManager() == null) {
84 LOGGER.error("No AbstractDatabaseManager set for the appender named [{}].", this.getName());
85 }
86 super.start();
87 if (this.getManager() != null) {
88 this.getManager().startup();
89 }
90 }
91
92 @Override
93 public final void stop() {
94 super.stop();
95 if (this.getManager() != null) {
96 this.getManager().release();
97 }
98 }
99
100 @Override
101 public final void append(final LogEvent event) {
102 this.readLock.lock();
103 try {
104 this.getManager().write(event);
105 } catch (final LoggingException e) {
106 LOGGER.error("Unable to write to database [{}] for appender [{}].", this.getManager().getName(),
107 this.getName(), e);
108 throw e;
109 } catch (final Exception e) {
110 LOGGER.error("Unable to write to database [{}] for appender [{}].", this.getManager().getName(),
111 this.getName(), e);
112 throw new AppenderLoggingException("Unable to write to database in appender: " + e.getMessage(), e);
113 } finally {
114 this.readLock.unlock();
115 }
116 }
117
118 /**
119 * Replaces the underlying manager in use within this appender. This can be useful for manually changing the way log
120 * events are written to the database without losing buffered or in-progress events. The existing manager is
121 * released only after the new manager has been installed. This method is thread-safe.
122 *
123 * @param manager The new manager to install.
124 */
125 protected final void replaceManager(final T manager) {
126 this.writeLock.lock();
127 try {
128 final T old = this.getManager();
129 if (!manager.isRunning()) {
130 manager.startup();
131 }
132 this.manager = manager;
133 old.release();
134 } finally {
135 this.writeLock.unlock();
136 }
137 }
138 }