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; 022import java.util.concurrent.TimeUnit; 023 024import org.apache.logging.log4j.LoggingException; 025import org.apache.logging.log4j.core.Appender; 026import org.apache.logging.log4j.core.Core; 027import org.apache.logging.log4j.core.Filter; 028import org.apache.logging.log4j.core.LogEvent; 029import org.apache.logging.log4j.core.config.AppenderControl; 030import org.apache.logging.log4j.core.config.Configuration; 031import org.apache.logging.log4j.core.config.Property; 032import org.apache.logging.log4j.core.config.plugins.Plugin; 033import org.apache.logging.log4j.core.config.plugins.PluginAliases; 034import org.apache.logging.log4j.core.config.plugins.PluginAttribute; 035import org.apache.logging.log4j.core.config.plugins.PluginConfiguration; 036import org.apache.logging.log4j.core.config.plugins.PluginElement; 037import org.apache.logging.log4j.core.config.plugins.PluginFactory; 038import org.apache.logging.log4j.core.util.Booleans; 039import org.apache.logging.log4j.core.util.Constants; 040 041/** 042 * The FailoverAppender will capture exceptions in an Appender and then route the event 043 * to a different appender. Hopefully it is obvious that the Appenders must be configured 044 * to not suppress exceptions for the FailoverAppender to work. 045 */ 046@Plugin(name = "Failover", category = Core.CATEGORY_NAME, elementType = Appender.ELEMENT_TYPE, printObject = true) 047public final class FailoverAppender extends AbstractAppender { 048 049 private static final int DEFAULT_INTERVAL_SECONDS = 60; 050 051 private final String primaryRef; 052 053 private final String[] failovers; 054 055 private final Configuration config; 056 057 private AppenderControl primary; 058 059 private final List<AppenderControl> failoverAppenders = new ArrayList<>(); 060 061 private final long intervalNanos; 062 063 private volatile long nextCheckNanos = 0; 064 065 private FailoverAppender(final String name, final Filter filter, final String primary, final String[] failovers, 066 final int intervalMillis, final Configuration config, final boolean ignoreExceptions, 067 final Property[] properties) { 068 super(name, filter, null, ignoreExceptions, properties); 069 this.primaryRef = primary; 070 this.failovers = failovers; 071 this.config = config; 072 this.intervalNanos = TimeUnit.MILLISECONDS.toNanos(intervalMillis); 073 } 074 075 @Override 076 public void start() { 077 final Map<String, Appender> map = config.getAppenders(); 078 int errors = 0; 079 final Appender appender = map.get(primaryRef); 080 if (appender != null) { 081 primary = new AppenderControl(appender, null, null); 082 } else { 083 LOGGER.error("Unable to locate primary Appender " + primaryRef); 084 ++errors; 085 } 086 for (final String name : failovers) { 087 final Appender foAppender = map.get(name); 088 if (foAppender != null) { 089 failoverAppenders.add(new AppenderControl(foAppender, null, null)); 090 } else { 091 LOGGER.error("Failover appender " + name + " is not configured"); 092 } 093 } 094 if (failoverAppenders.isEmpty()) { 095 LOGGER.error("No failover appenders are available"); 096 ++errors; 097 } 098 if (errors == 0) { 099 super.start(); 100 } 101 } 102 103 /** 104 * Handle the Log event. 105 * @param event The LogEvent. 106 */ 107 @Override 108 public void append(final LogEvent event) { 109 if (!isStarted()) { 110 error("FailoverAppender " + getName() + " did not start successfully"); 111 return; 112 } 113 final long localCheckNanos = nextCheckNanos; 114 if (localCheckNanos == 0 || System.nanoTime() - localCheckNanos > 0) { 115 callAppender(event); 116 } else { 117 failover(event, null); 118 } 119 } 120 121 private void callAppender(final LogEvent event) { 122 try { 123 primary.callAppender(event); 124 nextCheckNanos = 0; 125 } catch (final Exception ex) { 126 nextCheckNanos = System.nanoTime() + intervalNanos; 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 } 151 throw new LoggingException("Unable to write to failover appenders", failoverException); 152 } 153 } 154 155 @Override 156 public String toString() { 157 final StringBuilder sb = new StringBuilder(getName()); 158 sb.append(" primary=").append(primary).append(", failover={"); 159 boolean first = true; 160 for (final String str : failovers) { 161 if (!first) { 162 sb.append(", "); 163 } 164 sb.append(str); 165 first = false; 166 } 167 sb.append('}'); 168 return sb.toString(); 169 } 170 171 /** 172 * Create a Failover Appender. 173 * @param name The name of the Appender (required). 174 * @param primary The name of the primary Appender (required). 175 * @param failovers The name of one or more Appenders to fail over to (at least one is required). 176 * @param retryIntervalSeconds The retry interval in seconds. 177 * @param config The current Configuration (passed by the Configuration when the appender is created). 178 * @param filter A Filter (optional). 179 * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise 180 * they are propagated to the caller. 181 * @return The FailoverAppender that was created. 182 */ 183 @PluginFactory 184 public static FailoverAppender createAppender( 185 @PluginAttribute("name") final String name, 186 @PluginAttribute("primary") final String primary, 187 @PluginElement("Failovers") final String[] failovers, 188 @PluginAliases("retryInterval") // deprecated 189 @PluginAttribute("retryIntervalSeconds") final String retryIntervalSeconds, 190 @PluginConfiguration final Configuration config, 191 @PluginElement("Filter") 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(retryIntervalSeconds, DEFAULT_INTERVAL_SECONDS); 207 int retryIntervalMillis; 208 if (seconds >= 0) { 209 retryIntervalMillis = seconds * Constants.MILLIS_IN_SECONDS; 210 } else { 211 LOGGER.warn("Interval " + retryIntervalSeconds + " 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, null); 218 } 219}