doc/examples/java-jul/ApplicationContextExample.java

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2016 EfficiOS Inc.
   5  * Copyright (C) 2016 Alexandre Montplaisir <alexmonthy@efficios.com>
   6  */
   7
   8 import java.io.IOException;
   9 import java.util.logging.Handler;
  10 import java.util.logging.Logger;
  11
  12 import org.lttng.ust.agent.context.ContextInfoManager;
  13 import org.lttng.ust.agent.context.IContextInfoRetriever;
  14 import org.lttng.ust.agent.jul.LttngLogHandler;
  15
  16 /**
  17  * Example program defining a application context retriever, which allows
  18  * attaching application-defined contexts to trace events.
  19  *
  20  * FIXME Use custom context names, and several names/types
  21  *
  22  * <p>
  23  * Usage:
  24  * <ul>
  25  * <li>$ lttng create</li>
  26  * <li>$ lttng enable-event -j -a</li>
  27  * <li>$ lttng add-context -j -t '$app.myprovider:mystringcontext'</li>
  28  * <li>$ lttng add-context -j -t '$app.myprovider:myshortcontext'</li>
  29  * <li>$ lttng start</li>
  30  * <li>(run this program)</li>
  31  * <li>$ lttng stop</li>
  32  * <li>$ lttng view</li>
  33  * <li>$ lttng destroy</li>
  34  * </ul>
  35  * </p>
  36  *
  37  * The events present in the resulting trace should carry the context
  38  * information defined in the example retriever.
  39  *
  40  * @author Alexandre Montplaisir
  41  */
  42 public class ApplicationContextExample {
  43
  44         /** Class-wide JUL logger object */
  45         private static final Logger LOGGER = Logger.getLogger(ApplicationContextExample.class.getName());
  46
  47         private static final String RETRIEVER_NAME = "myprovider";
  48         private static final String CONTEXT_NAME_STRING = "mystringcontext";
  49         private static final String CONTEXT_NAME_SHORT = "myshortcontext";
  50
  51         private static class ExampleContextInfoRetriever implements IContextInfoRetriever {
  52
  53                 @Override
  54                 public Object retrieveContextInfo(String key) {
  55                         if (CONTEXT_NAME_SHORT.equals(key)) {
  56                                 return (short) 42;
  57                         } else if (CONTEXT_NAME_STRING.equals(key)) {
  58                                 return "context-value!";
  59                         } else {
  60                                 return null;
  61                         }
  62                 }
  63
  64         }
  65
  66         /**
  67          * Application start
  68          *
  69          * @param args
  70          *            Command-line arguments
  71          * @throws IOException
  72          * @throws InterruptedException
  73          */
  74         public static void main(String args[]) throws IOException, InterruptedException {
  75                 /* Instantiate and attach a logger object */
  76                 Handler lttngHandler = new LttngLogHandler();
  77                 LOGGER.addHandler(lttngHandler);
  78
  79                 /* Instantiate and register the context retriever */
  80                 IContextInfoRetriever cir = new ExampleContextInfoRetriever();
  81                 ContextInfoManager.getInstance().registerContextInfoRetriever(RETRIEVER_NAME, cir);
  82
  83                 /*
  84                  * Make sure you have a LTTng session running with the appropriate
  85                  * events and contexts enabled! See the class Javadoc.
  86                  */
  87
  88                 /* Trigger a tracing event using the JUL Logger created before. */
  89                 LOGGER.info("Log event #1");
  90                 LOGGER.warning("Log event #2");
  91                 LOGGER.severe("Log event #3");
  92
  93                 /* Unregister our context retriever, and dispose the log handler */
  94                 ContextInfoManager.getInstance().unregisterContextInfoRetriever(RETRIEVER_NAME);
  95                 lttngHandler.close();
  96         }
  97 }