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From "Ivan A. Veselovsky (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9269) o.a.h.metrics2: annotation @Metric(...,always=true) does not work as expected
Date Thu, 31 Jan 2013 14:47:15 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13567680#comment-13567680
] 

Ivan A. Veselovsky commented on HADOOP-9269:
--------------------------------------------

afaik, the field metrics are created in method org.apache.hadoop.metrics2.lib.MutableMetricsFactory.newForField(Field,
Metric, MetricsRegistry), and the value of @Metric#always is just ignored in case of MutableCounter/Gauge
classes.
Also, in case of MurableStat/Rate the "always" value is used as "extended" parameter, which
has another meaning: "produce extended stat (stdev, min/max etc.) if true.". 
It looks like there is a mess with this annotation parameter.
                
> o.a.h.metrics2: annotation @Metric(...,always=true) does not work as expected
> -----------------------------------------------------------------------------
>
>                 Key: HADOOP-9269
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9269
>             Project: Hadoop Common
>          Issue Type: Bug
>            Reporter: Ivan A. Veselovsky
>
> {noformat}Metrics2: 
> if a metric defined via annotations, like this 
> @Metric(....,always=true), it should be snapshotted always, as defined by the "always"
attribute description: 
>   /**
>    * @return true to create a metric snapshot even if unchanged.
>    */
>   boolean always() default false;
> However, that does not work in that way. 
> The problem can be reproduced with the following test:
> public class TestBugDemo {
>   @Metrics(name="record1", context="context1")
>   static class MyMetrics1 {
>     
>     @Metric(value={"annotatedMetric1", "An integer gauge"},always=true) 
>     MutableGaugeInt testMetric1;
>     public MyMetrics1 registerWith(MetricsSystem ms) {
>       return ms.register("annotated", "annotated", this);
>     }
>   }
>   
>   private static class MySink implements MetricsSink {
>     private final String sinkName;
>     public MySink(String name) {
>       sinkName = name;
>     }
>     @Override
>     public void init(SubsetConfiguration conf) {
>     }
>     @Override
>     public void flush() {
>     }
>     @Override
>     public void putMetrics(MetricsRecord record) {
>       if (!"metricssystem".equals(record.context())) {
>         for (AbstractMetric am: record.metrics()) {
>           System.out.println("### METRIC: " + am.name() + " = " + am.value());
>         }
>       }
>     }
>   }
>   
>   private MetricsSystem ms;
>   MyMetrics1 m1;
>   
>   @Before
>   public void before() {
>     ms = DefaultMetricsSystem.initialize("");
>     // register annotated source:
>     m1 = new MyMetrics1().registerWith(ms);
>     
>     // register not-annotated source:
>     final MetricsInfo fooInfo = Interns.info("non-annotated metric foo", "foo descrption");
>     ms.register("not-annotatad", "", new MetricsSource() {
>       @Override
>       public void getMetrics(MetricsCollector collector, boolean all) {
>         collector
>           .addRecord("testRecord")
>           .addCounter(fooInfo, 88)
>           .setContext("test1")
>           .endRecord();
>       }
>     });
>     
>     ms.register("sink1", null, new MySink("sink1"));
>   }
>   
>   @Test
>   public void testAlways() {
>     m1.testMetric1.set(5);
>     System.out.println("First  Pubishing: ===========================================================");
>     ms.publishMetricsNow();
>     
>     //m1.testMetric1.set(7);
>     System.out.println("Second Pubishing: ===========================================================");
>     ms.publishMetricsNow();
>   }
>   
> }
> This test generates the following output:
> First  Pubishing: ===========================================================
> ### METRIC: annotatedMetric1 = 5
> ### METRIC: non-annotated metric foo = 88
> Second Pubishing: ===========================================================
> ### METRIC: non-annotated metric foo = 88
> That is, the metric "annotatedMetric1" is absent in the 2nd snapshot.
> Once we uncomment the line "//m1.testMetric1.set(7);", we observe expected behavior:
> First  Pubishing: ===========================================================
> ### METRIC: annotatedMetric1 = 5
> ### METRIC: non-annotated metric foo = 88
> Second Pubishing: ===========================================================
> ### METRIC: annotatedMetric1 = 7
> ### METRIC: non-annotated metric foo = 88
> The expected behavior is that the metric "annotatedMetric1" will be snapshotted even
if it was not changed, because it is annotated with "always=true". 
> {noformat}

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