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Create a custom PMI using StatsFactory

We can update the application to call methods defined using A Stats/PMI template (Performance Monitoring Infrastructure), resource bundle, Stats/PMI module and methods to update custom statistics.

We can update the application to call methods defined using A Stats/PMI template, resource bundle, Stats/PMI module and methods to update custom statistics. The following process is required to instrument a component using a custom PMI:

• Define a Stats/PMI template (xml file).
• Define the resource bundle (properties file).
• Define the Stats/PMI module and create the Stats/PMI object using StatsFactory.
• Define methods that the application will use to update custom statistics.
• Update the application to call methods (defined in the preceding step) appropriately.
• Access the application.
• Connect to the Tivoli Performance Viewer (TPV) and view the Custom PMI statistics.

Procedure

1. Define the Stats/PMI template. StatsFactory allows a runtime component to create a custom Stats/PMI module using an XML template. The template should follow the DTD com/ibm/websphere/pmi/xml/stats.dtd. The following is an example of a template used in a sample application.

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE Stats SYSTEM "stats.dtd">
   
   <Stats type="com.stats.MyStats">
   <description>MyStats.desc
   </description>
   <resourceBundle>com.stats.MyStatsResourceBundle
   </resourceBundle>      
   
   <CountStatistic ID="1" name="MyStats.NumRequests">  
   <level>low
   </level>  
   <unit>MyStats.unit.none
   </unit>         
    
   <description>MyStats.NumRequests.desc
   </description>
    
   <statisticSet>basic
   </statisticSet>      
   
   </CountStatistic>
   
   
   <BoundedRangeStatistic ID="2" name="MyStats.expensiveStat ">  
   <level>high
   </level>  
   <unit>MyStats.unit.none
   </unit>  
   <description>MyStats.expensiveStat.desc
   </description>  
   <updateOnRequest>true
   </updateOnRequest> 
   
   </BoundedRangeStatistic>
   
   </Stats> 

2. Define the resource bundle The resource bundle allows you to define the name of statistic and its description in proper language/wording. A sample resource bundle would look like this:

   MyStats.desc=My View PMI Module
   
   MyStats.NumRequests=Request Count
   MyStats.NumRequests.desc=Total number of My view requests served.
   MyStats.unit.none=None
   
   
   MyStats.expensiveStat = Expensive Stat
   MyStats. expensiveStat.desc = Number of Expensive stats
   
   MyStats.Group= My Group
   MyStats.Instance=My Instance
   

3. Define the Stats/PMI module and create the Stats/PMI object using StatsFactory.

   1. Create a class which extends StatisticActions

      public class MyStatisticsModule extends StatisticActions
      

   2. Declare count variables of type SPI*, such as :SPICountStatistc and SPIBoundedRangeStatistic.

      private SPICountStatistic           numReqs;
       private SPIBoundedRangeStatistic    expensiveStat;
      

   3. Create StatsGroup of type StatsGroup and StatsInstance of type StatsInstance

      private static StatsGroup stocksStatisticsGroup = null;
       private StatsInstance stocksStatistics = null;
      
      
      MyStatisticsGroup = StatsFactory.createStatsGroup("MyStats.Group", template, null);
      MyStatistics = StatsFactory.createStatsInstance("MyStats.Instance”,MyStatisticGroup,null,this);
      

      where the template would be the path in the application where the xml file is located. An example of this follows:

      String template = "/com/stats/MyStats.xml";
      

4. Once the Statistics are created in the StatsInstance, statisticCreated is called to indicate that a statistic is created in the Stats instance. .We can assign statistics declared above to the appropriate statistic. An example follows:

   public void statisticCreated (SPIStatistic s)      --> Called when the Statistics are  created in the Stats Instance
        {
        if (s.getId() == MyStats.NUMREQS)
            {
                numReqs = (SPICountStatistic)s;       ---> Assign Statistic
           }
   }
   

5. Define methods which the application will use to update custom statistics.

   public void onRequestArrival(){
        if (numReqs != null)
           {
               numReqs.increment();         ---> Increment/Decrement Statistic as per Req
   }
   

6. We can also implement the updateStaisticRequest method to update statistics on a specific request by the client or any other monitoring application.

   public void updateStatisticOnRequest (int dataId)
     {
   if (dataId == MyStats.expensiveStat)
            {
             expensiveStat.set(xxxxx); 
     }
   
   }
   

   In the above example, dataId would be the id of the statistic that is to be updated.
7. Update the application to call methods (defined in above steps) appropriately.
8. Access the application.
9. Connect Tivoli Performance Viewer and view the custom PMI statistics.

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