    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    }