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.util.ArrayList;
020 import java.util.List;
021 import java.util.Map;
022
023 import org.apache.logging.log4j.LoggingException;
024 import org.apache.logging.log4j.core.Appender;
025 import org.apache.logging.log4j.core.Filter;
026 import org.apache.logging.log4j.core.LogEvent;
027 import org.apache.logging.log4j.core.config.AppenderControl;
028 import org.apache.logging.log4j.core.config.Configuration;
029 import org.apache.logging.log4j.core.config.plugins.Plugin;
030 import org.apache.logging.log4j.core.config.plugins.PluginAliases;
031 import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
032 import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
033 import org.apache.logging.log4j.core.config.plugins.PluginElement;
034 import org.apache.logging.log4j.core.config.plugins.PluginFactory;
035 import org.apache.logging.log4j.core.util.Booleans;
036 import org.apache.logging.log4j.core.util.Constants;
037
038 /**
039 * The FailoverAppender will capture exceptions in an Appender and then route the event
040 * to a different appender. Hopefully it is obvious that the Appenders must be configured
041 * to not suppress exceptions for the FailoverAppender to work.
042 */
043 @Plugin(name = "Failover", category = "Core", elementType = "appender", printObject = true)
044 public final class FailoverAppender extends AbstractAppender {
045
046 private static final long serialVersionUID = 1L;
047
048 private static final int DEFAULT_INTERVAL_SECONDS = 60;
049
050 private final String primaryRef;
051
052 private final String[] failovers;
053
054 private final Configuration config;
055
056 private AppenderControl primary;
057
058 private final List<AppenderControl> failoverAppenders = new ArrayList<AppenderControl>();
059
060 private final long intervalMillis;
061
062 private volatile long nextCheckMillis = 0;
063
064 private FailoverAppender(final String name, final Filter filter, final String primary, final String[] failovers,
065 final int intervalMillis, final Configuration config, final boolean ignoreExceptions) {
066 super(name, filter, null, ignoreExceptions);
067 this.primaryRef = primary;
068 this.failovers = failovers;
069 this.config = config;
070 this.intervalMillis = intervalMillis;
071 }
072
073
074 @Override
075 public void start() {
076 final Map<String, Appender> map = config.getAppenders();
077 int errors = 0;
078 if (map.containsKey(primaryRef)) {
079 primary = new AppenderControl(map.get(primaryRef), null, null);
080 } else {
081 LOGGER.error("Unable to locate primary Appender " + primaryRef);
082 ++errors;
083 }
084 for (final String name : failovers) {
085 if (map.containsKey(name)) {
086 failoverAppenders.add(new AppenderControl(map.get(name), null, null));
087 } else {
088 LOGGER.error("Failover appender " + name + " is not configured");
089 }
090 }
091 if (failoverAppenders.isEmpty()) {
092 LOGGER.error("No failover appenders are available");
093 ++errors;
094 }
095 if (errors == 0) {
096 super.start();
097 }
098 }
099
100 /**
101 * Handle the Log event.
102 * @param event The LogEvent.
103 */
104 @Override
105 public void append(final LogEvent event) {
106 if (!isStarted()) {
107 error("FailoverAppender " + getName() + " did not start successfully");
108 return;
109 }
110 final long localCheckMillis = nextCheckMillis;
111 if (localCheckMillis == 0 || System.currentTimeMillis() > localCheckMillis) {
112 callAppender(event);
113 } else {
114 failover(event, null);
115 }
116 }
117
118 private void callAppender(final LogEvent event) {
119 try {
120 primary.callAppender(event);
121 nextCheckMillis = 0;
122 } catch (final Exception ex) {
123 nextCheckMillis = System.currentTimeMillis() + intervalMillis;
124 failover(event, ex);
125 }
126 }
127
128 private void failover(final LogEvent event, final Exception ex) {
129 final RuntimeException re = ex != null ?
130 (ex instanceof LoggingException ? (LoggingException)ex : new LoggingException(ex)) : null;
131 boolean written = false;
132 Exception failoverException = null;
133 for (final AppenderControl control : failoverAppenders) {
134 try {
135 control.callAppender(event);
136 written = true;
137 break;
138 } catch (final Exception fex) {
139 if (failoverException == null) {
140 failoverException = fex;
141 }
142 }
143 }
144 if (!written && !ignoreExceptions()) {
145 if (re != null) {
146 throw re;
147 }
148 throw new LoggingException("Unable to write to failover appenders", failoverException);
149 }
150 }
151
152 @Override
153 public String toString() {
154 final StringBuilder sb = new StringBuilder(getName());
155 sb.append(" primary=").append(primary).append(", failover={");
156 boolean first = true;
157 for (final String str : failovers) {
158 if (!first) {
159 sb.append(", ");
160 }
161 sb.append(str);
162 first = false;
163 }
164 sb.append('}');
165 return sb.toString();
166 }
167
168 /**
169 * Create a Failover Appender.
170 * @param name The name of the Appender (required).
171 * @param primary The name of the primary Appender (required).
172 * @param failovers The name of one or more Appenders to fail over to (at least one is required).
173 * @param retryIntervalSeconds The retry interval in seconds.
174 * @param config The current Configuration (passed by the Configuration when the appender is created).
175 * @param filter A Filter (optional).
176 * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
177 * they are propagated to the caller.
178 * @return The FailoverAppender that was created.
179 */
180 @PluginFactory
181 public static FailoverAppender createAppender(
182 @PluginAttribute("name") final String name,
183 @PluginAttribute("primary") final String primary,
184 @PluginElement("Failovers") final String[] failovers,
185 @PluginAliases("retryInterval") // deprecated
186 @PluginAttribute("retryIntervalSeconds") final String retryIntervalSeconds,
187 @PluginConfiguration final Configuration config,
188 @PluginElement("Filter") final Filter filter,
189 @PluginAttribute("ignoreExceptions") final String ignore) {
190 if (name == null) {
191 LOGGER.error("A name for the Appender must be specified");
192 return null;
193 }
194 if (primary == null) {
195 LOGGER.error("A primary Appender must be specified");
196 return null;
197 }
198 if (failovers == null || failovers.length == 0) {
199 LOGGER.error("At least one failover Appender must be specified");
200 return null;
201 }
202
203 final int seconds = parseInt(retryIntervalSeconds, DEFAULT_INTERVAL_SECONDS);
204 int retryIntervalMillis;
205 if (seconds >= 0) {
206 retryIntervalMillis = seconds * Constants.MILLIS_IN_SECONDS;
207 } else {
208 LOGGER.warn("Interval " + retryIntervalSeconds + " is less than zero. Using default");
209 retryIntervalMillis = DEFAULT_INTERVAL_SECONDS * Constants.MILLIS_IN_SECONDS;
210 }
211
212 final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
213
214 return new FailoverAppender(name, filter, primary, failovers, retryIntervalMillis, config, ignoreExceptions);
215 }
216 }