liblttng-ust-java-agent/java/lttng-ust-agent-log4j/org/lttng/ust/agent/log4j/LttngLog4jAgent.java

   1 /*
   2  * Copyright (C) 2015 - EfficiOS Inc., Alexandre Montplaisir <alexmonthy@efficios.com>
   3  *
   4  * This library is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This library is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  11  * for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 package org.lttng.ust.agent.log4j;
  19
  20 import java.util.Collection;
  21 import java.util.Collections;
  22 import java.util.List;
  23 import java.util.Set;
  24 import java.util.TreeSet;
  25
  26 import org.apache.log4j.Appender;
  27 import org.apache.log4j.Category;
  28 import org.apache.log4j.LogManager;
  29 import org.apache.log4j.Logger;
  30 import org.lttng.ust.agent.AbstractLttngAgent;
  31
  32 /**
  33  * Agent implementation for using the Log4j logger, connecting to a root session
  34  * daemon.
  35  *
  36  * @author Alexandre Montplaisir
  37  */
  38 class LttngLog4jAgent extends AbstractLttngAgent<LttngLogAppender> {
  39
  40         private static LttngLog4jAgent instance = null;
  41
  42         private LttngLog4jAgent() {
  43                 super(Domain.LOG4J);
  44         }
  45
  46         public static synchronized LttngLog4jAgent getInstance() {
  47                 if (instance == null) {
  48                         instance = new LttngLog4jAgent();
  49                 }
  50                 return instance;
  51         }
  52
  53         @Override
  54         public Collection<String> listAvailableEvents() {
  55                 Set<String> ret = new TreeSet<String>();
  56
  57                 @SuppressWarnings("unchecked")
  58                 List<Logger> loggers = Collections.list(LogManager.getCurrentLoggers());
  59                 for (Logger logger : loggers) {
  60                         if (logger == null) {
  61                                 continue;
  62                         }
  63
  64                         /*
  65                          * Check if that logger has at least one LTTng log4j appender
  66                          * attached.
  67                          */
  68                         if (hasLttngAppenderAttached(logger)) {
  69                                 ret.add(logger.getName());
  70                         }
  71                 }
  72
  73                 return ret;
  74         }
  75
  76         private static boolean hasLttngAppenderAttached(Category logger) {
  77                 @SuppressWarnings("unchecked")
  78                 List<Appender> appenders = Collections.list(logger.getAllAppenders());
  79                 for (Appender appender : appenders) {
  80                         if (appender instanceof LttngLogAppender) {
  81                                 return true;
  82                         }
  83                 }
  84
  85                 /*
  86                  * A parent logger, if any, may be connected to an LTTng handler. In
  87                  * this case, we will want to include this child logger in the output,
  88                  * since it will be accessible by LTTng.
  89                  */
  90                 Category parent = logger.getParent();
  91                 if (parent != null) {
  92                         return hasLttngAppenderAttached(parent);
  93                 }
  94
  95                 /*
  96                  * We have reached the root logger and have not found any LTTng handler,
  97                  * this event will not be accessible.
  98                  */
  99                 return false;
 100         }
 101
 102 }