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 */ 017package org.apache.logging.log4j.core.appender; 018 019import java.util.ArrayList; 020import java.util.List; 021import java.util.Map; 022 023import org.apache.logging.log4j.LoggingException; 024import org.apache.logging.log4j.core.Appender; 025import org.apache.logging.log4j.core.Filter; 026import org.apache.logging.log4j.core.LogEvent; 027import org.apache.logging.log4j.core.config.AppenderControl; 028import org.apache.logging.log4j.core.config.Configuration; 029import org.apache.logging.log4j.core.config.plugins.Plugin; 030import org.apache.logging.log4j.core.config.plugins.PluginAttribute; 031import org.apache.logging.log4j.core.config.plugins.PluginConfiguration; 032import org.apache.logging.log4j.core.config.plugins.PluginElement; 033import org.apache.logging.log4j.core.config.plugins.PluginFactory; 034import org.apache.logging.log4j.core.helpers.Booleans; 035import org.apache.logging.log4j.core.helpers.Constants; 036 037/** 038 * The FailoverAppender will capture exceptions in an Appender and then route the event 039 * to a different appender. Hopefully it is obvious that the Appenders must be configured 040 * to not suppress exceptions for the FailoverAppender to work. 041 */ 042@Plugin(name = "Failover", category = "Core", elementType = "appender", printObject = true) 043public final class FailoverAppender extends AbstractAppender { 044 045 private static final int DEFAULT_INTERVAL_SECONDS = 60; 046 047 private final String primaryRef; 048 049 private final String[] failovers; 050 051 private final Configuration config; 052 053 private AppenderControl primary; 054 055 private final List<AppenderControl> failoverAppenders = new ArrayList<AppenderControl>(); 056 057 private final long intervalMillis; 058 059 private long nextCheckMillis = 0; 060 061 private volatile boolean failure = false; 062 063 private FailoverAppender(final String name, final Filter filter, final String primary, final String[] failovers, 064 final int intervalMillis, final Configuration config, final boolean ignoreExceptions) { 065 super(name, filter, null, ignoreExceptions); 066 this.primaryRef = primary; 067 this.failovers = failovers; 068 this.config = config; 069 this.intervalMillis = intervalMillis; 070 } 071 072 073 @Override 074 public void start() { 075 final Map<String, Appender> map = config.getAppenders(); 076 int errors = 0; 077 if (map.containsKey(primaryRef)) { 078 primary = new AppenderControl(map.get(primaryRef), null, null); 079 } else { 080 LOGGER.error("Unable to locate primary Appender " + primaryRef); 081 ++errors; 082 } 083 for (final String name : failovers) { 084 if (map.containsKey(name)) { 085 failoverAppenders.add(new AppenderControl(map.get(name), null, null)); 086 } else { 087 LOGGER.error("Failover appender " + name + " is not configured"); 088 } 089 } 090 if (failoverAppenders.size() == 0) { 091 LOGGER.error("No failover appenders are available"); 092 ++errors; 093 } 094 if (errors == 0) { 095 super.start(); 096 } 097 } 098 099 /** 100 * Handle the Log event. 101 * @param event The LogEvent. 102 */ 103 @Override 104 public void append(final LogEvent event) { 105 if (!isStarted()) { 106 error("FailoverAppender " + getName() + " did not start successfully"); 107 return; 108 } 109 if (!failure) { 110 callAppender(event); 111 } else { 112 final long currentMillis = System.currentTimeMillis(); 113 if (currentMillis >= nextCheckMillis) { 114 callAppender(event); 115 } else { 116 failover(event, null); 117 } 118 } 119 } 120 121 private void callAppender(final LogEvent event) { 122 try { 123 primary.callAppender(event); 124 } catch (final Exception ex) { 125 nextCheckMillis = System.currentTimeMillis() + intervalMillis; 126 failure = true; 127 failover(event, ex); 128 } 129 } 130 131 private void failover(final LogEvent event, final Exception ex) { 132 final RuntimeException re = ex != null ? 133 (ex instanceof LoggingException ? (LoggingException)ex : new LoggingException(ex)) : null; 134 boolean written = false; 135 Exception failoverException = null; 136 for (final AppenderControl control : failoverAppenders) { 137 try { 138 control.callAppender(event); 139 written = true; 140 break; 141 } catch (final Exception fex) { 142 if (failoverException == null) { 143 failoverException = fex; 144 } 145 } 146 } 147 if (!written && !ignoreExceptions()) { 148 if (re != null) { 149 throw re; 150 } else { 151 throw new LoggingException("Unable to write to failover appenders", failoverException); 152 } 153 } 154 } 155 156 @Override 157 public String toString() { 158 final StringBuilder sb = new StringBuilder(getName()); 159 sb.append(" primary=").append(primary).append(", failover={"); 160 boolean first = true; 161 for (final String str : failovers) { 162 if (!first) { 163 sb.append(", "); 164 } 165 sb.append(str); 166 first = false; 167 } 168 sb.append("}"); 169 return sb.toString(); 170 } 171 172 /** 173 * Create a Failover Appender. 174 * @param name The name of the Appender (required). 175 * @param primary The name of the primary Appender (required). 176 * @param failovers The name of one or more Appenders to fail over to (at least one is required). 177 * @param retryIntervalString The retry intervalMillis. 178 * @param config The current Configuration (passed by the Configuration when the appender is created). 179 * @param filter A Filter (optional). 180 * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise 181 * they are propagated to the caller. 182 * @return The FailoverAppender that was created. 183 */ 184 @PluginFactory 185 public static FailoverAppender createAppender( 186 @PluginAttribute("name") final String name, 187 @PluginAttribute("primary") final String primary, 188 @PluginElement("Failovers") final String[] failovers, 189 @PluginAttribute("retryInterval") final String retryIntervalString, 190 @PluginConfiguration final Configuration config, 191 @PluginElement("Filters") final Filter filter, 192 @PluginAttribute("ignoreExceptions") final String ignore) { 193 if (name == null) { 194 LOGGER.error("A name for the Appender must be specified"); 195 return null; 196 } 197 if (primary == null) { 198 LOGGER.error("A primary Appender must be specified"); 199 return null; 200 } 201 if (failovers == null || failovers.length == 0) { 202 LOGGER.error("At least one failover Appender must be specified"); 203 return null; 204 } 205 206 final int seconds = parseInt(retryIntervalString, DEFAULT_INTERVAL_SECONDS); 207 int retryIntervalMillis; 208 if (seconds >= 0) { 209 retryIntervalMillis = seconds * Constants.MILLIS_IN_SECONDS; 210 } else { 211 LOGGER.warn("Interval " + retryIntervalString + " is less than zero. Using default"); 212 retryIntervalMillis = DEFAULT_INTERVAL_SECONDS * Constants.MILLIS_IN_SECONDS; 213 } 214 215 final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true); 216 217 return new FailoverAppender(name, filter, primary, failovers, retryIntervalMillis, config, ignoreExceptions); 218 } 219}