liblttng-ust-java-agent/java/lttng-ust-agent-jul/org/lttng/ust/agent/jul/LttngJulAgent.java

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2015 EfficiOS Inc.
   5  * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com>
   6  */
   7
   8 package org.lttng.ust.agent.jul;
   9
  10 import java.util.Collection;
  11 import java.util.Collections;
  12 import java.util.List;
  13 import java.util.Set;
  14 import java.util.TreeSet;
  15 import java.util.logging.Handler;
  16 import java.util.logging.LogManager;
  17 import java.util.logging.Logger;
  18
  19 import org.lttng.ust.agent.AbstractLttngAgent;
  20
  21 /**
  22  * Agent implementation for tracing from JUL loggers.
  23  *
  24  * @author Alexandre Montplaisir
  25  */
  26 class LttngJulAgent extends AbstractLttngAgent<LttngLogHandler> {
  27
  28         private static LttngJulAgent instance = null;
  29
  30         private LttngJulAgent() {
  31                 super(Domain.JUL);
  32         }
  33
  34         public static synchronized LttngJulAgent getInstance() {
  35                 if (instance == null) {
  36                         instance = new LttngJulAgent();
  37                 }
  38                 return instance;
  39         }
  40
  41         @Override
  42         public Collection<String> listAvailableEvents() {
  43                 Set<String> ret = new TreeSet<String>();
  44
  45                 List<String> loggersNames = Collections.list(LogManager.getLogManager().getLoggerNames());
  46                 for (String name : loggersNames) {
  47                         /*
  48                          * Skip the root logger. An empty string is not a valid event name
  49                          * in LTTng.
  50                          */
  51                         if (name.equals("") || name.equals("global")) {
  52                                 continue;
  53                         }
  54
  55                         /*
  56                          * Check if that logger has at least one LTTng JUL handler attached.
  57                          */
  58                         Logger logger = Logger.getLogger(name);
  59                         if (hasLttngHandlerAttached(logger)) {
  60                                 ret.add(name);
  61                         }
  62                 }
  63
  64                 return ret;
  65         }
  66
  67         private static boolean hasLttngHandlerAttached(Logger logger) {
  68                 for (Handler handler : logger.getHandlers()) {
  69                         if (handler instanceof LttngLogHandler) {
  70                                 return true;
  71                         }
  72                 }
  73
  74                 /*
  75                  * A parent logger, if any, may be connected to an LTTng handler. In
  76                  * this case, we will want to include this child logger in the output,
  77                  * since it will be accessible by LTTng.
  78                  */
  79                 Logger parent = logger.getParent();
  80                 if (parent != null) {
  81                         return hasLttngHandlerAttached(parent);
  82                 }
  83
  84                 /*
  85                  * We have reached the root logger and have not found any LTTng handler,
  86                  * this event will not be accessible.
  87                  */
  88                 return false;
  89         }
  90
  91 }