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.Enumeration;
  23 import java.util.List;
  24 import java.util.Set;
  25 import java.util.TreeSet;
  26
  27 import org.apache.log4j.Appender;
  28 import org.apache.log4j.Category;
  29 import org.apache.log4j.LogManager;
  30 import org.apache.log4j.Logger;
  31 import org.lttng.ust.agent.AbstractLttngAgent;
  32
  33 /**
  34  * Agent implementation for using the Log4j logger, connecting to a root session
  35  * daemon.
  36  *
  37  * @author Alexandre Montplaisir
  38  */
  39 class LttngLog4jAgent extends AbstractLttngAgent<LttngLogAppender> {
  40
  41         private static LttngLog4jAgent instance = null;
  42
  43         private LttngLog4jAgent() {
  44                 super(Domain.LOG4J);
  45         }
  46
  47         public static synchronized LttngLog4jAgent getInstance() {
  48                 if (instance == null) {
  49                         instance = new LttngLog4jAgent();
  50                 }
  51                 return instance;
  52         }
  53
  54         @Override
  55         public Collection<String> listAvailableEvents() {
  56                 Set<String> ret = new TreeSet<String>();
  57
  58                 @SuppressWarnings("unchecked")
  59                 List<Logger> loggers = Collections.list(LogManager.getCurrentLoggers());
  60                 for (Logger logger : loggers) {
  61                         if (logger == null) {
  62                                 continue;
  63                         }
  64
  65                         /*
  66                          * Check if that logger has at least one LTTng log4j appender
  67                          * attached.
  68                          */
  69                         if (hasLttngAppenderAttached(logger)) {
  70                                 ret.add(logger.getName());
  71                         }
  72                 }
  73
  74                 return ret;
  75         }
  76
  77         private static boolean hasLttngAppenderAttached(Category logger) {
  78                 @SuppressWarnings("unchecked")
  79                 Enumeration<Appender> appenders = logger.getAllAppenders();
  80                 if (appenders != null) {
  81                         for (Appender appender : Collections.list(appenders)) {
  82                                 if (appender instanceof LttngLogAppender) {
  83                                         return true;
  84                                 }
  85                         }
  86                 }
  87
  88                 /*
  89                  * A parent logger, if any, may be connected to an LTTng handler. In
  90                  * this case, we will want to include this child logger in the output,
  91                  * since it will be accessible by LTTng.
  92                  */
  93                 Category parent = logger.getParent();
  94                 if (parent != null) {
  95                         return hasLttngAppenderAttached(parent);
  96                 }
  97
  98                 /*
  99                  * We have reached the root logger and have not found any LTTng handler,
 100                  * this event will not be accessible.
 101                  */
 102                 return false;
 103         }
 104
 105 }