Package com.ocient.metrics

Class MetricsRegistry

java.lang.Object
com.ocient.metrics.MetricsRegistry
public class MetricsRegistry
extends Object
Global Registry for all performance counters.

In the example below I've added both INCREMENTAL_VALUE and INSTANTANEOUS_VALUE performance counters for a queue implementation with add() and poll() methods. The perf counters are used to track:

  • Cumulative number of elements processed by the queue (Countertype.INCREMENTAL)
  • Cumulative number of bytes processed by the queue (Countertype.INCREMENTAL)
  • Cumulative number of elements currently in the queue (Countertype.INSTANTANEOUS)
  • Cumulative number of bytes currently consumed by the queue (Countertype.INSTANTANEOUS)
The counters are retrieved from the registry in the ExampleQueue constructor and are removed in the shutdown() method. Unfortunately, we can't rely on object finalization to clean orphaned metrics. 

 private static class ExampleQueue {
     PerfCounter m_numElementsProcessed;
     PerfCounter m_numBytesProcessed;
     PerfCounter m_numElements;
     PerfCounter m_numBytesUsed;

     ExampleQueue(final int processingGroup, final int processingCore) {
         // Generate paths for all of the counters
         final List<NamedTag> tags = Arrays.asList(
             NamedTag.id(Tag.PROCESSING_GROUP, processingGroup),
             NamedTag.id(Tag.PROCESSING_CORE, processingCore));

         final Path nepPath = Path.create("extractor.exampleQueue.numElementsProcessed", tags);
         final Path nbpPath = Path.create("extractor.exampleQueue.numBytesProcessed", tags);
         final Path cnbPath = Path.create("extractor.exampleQueue.numElements", tags);
         final Path cnePath = Path.create("extractor.exampleQueue.numBytesUsed", tags);

         // Maintain references to these counters to avoid subsequent map lookups
         this.m_numElementsProcessed = MetricsRegistry.instance().getCounter(nepPath, ThreadingModel.NO_CONTENTION, DataType.LONG, CounterType.INCREMENTAL_VALUE, Units.UNITLESS);
         this.m_numBytesProcessed = MetricsRegistry.instance().getCounter(nbpPath, ThreadingModel.NO_CONTENTION, DataType.LONG, CounterType.INCREMENTAL_VALUE, Units.BYTES);
         this.m_numElements = MetricsRegistry.instance().getCounter(cnbPath, ThreadingModel.NO_CONTENTION, DataType.LONG, CounterType.INSTANTANEOUS_VALUE, Units.UNITLESS);
         this.m_numBytesUsed = MetricsRegistry.instance().getCounter(cnePath, ThreadingModel.NO_CONTENTION, DataType.LONG, CounterType.INSTANTANEOUS_VALUE, Units.BYTES);
     }

     void shutdown() {
         MetricsRegistry.instance().removeCounter(this.m_numElementsProcessed.path());
         MetricsRegistry.instance().removeCounter(this.m_numBytesProcessed.path());
         MetricsRegistry.instance().removeCounter(this.m_numElements.path());
         MetricsRegistry.instance().removeCounter(this.m_numBytesUsed.path());
     }

     void add(final Object o) {
         //... store o in memory
         this.m_numElements.incValue(1);
         this.m_numBytesUsed.incValue(getBytes(o));
     }

     Object poll() {
         //... poll object
         this.m_numElements.decValue(1);
         this.m_numBytesUsed.decValue(getBytes(o));
         this.m_numElementsProcessed.incValue(1);
         this.m_numBytesProcessed.incValue(getBytes(o));
         //... return polled object
     }
 }

  • Method Details

    • instance

      public static MetricsRegistry instance()
      Returns:
      the global PerfCounter registry

    • getCounter

      public PerfCounter getCounter​(Metric.MetricPath path, PerfCounter.ThreadingModel threadingModel, Metric.DataType dataType, Metric.CounterType counterType, Metric.Units units)
      Fetches a PerfCounter or creates one if no such counter exists.

      For example, to retrieve the counter for "extractor.examplePath" tagged with PROCESSING_GROUP=0: 

      
 final Path path = Path.create("extractor.examplePath", Arrays.asList(NamedTag.id(Tag.PROCESSING_GROUP, 0));
 PerfCounter counter = PerfRegistry.instance().getCounter(path, ThreadingModel.NO_CONTENTION, DataType.LONG, CounterType.INCREMENTAL_VALUE, Units.UNITLESS);
      Parameters:
      path - the path for the counter, should be unique to this counter
      threadingModel - the threading model under which the counter will be mutated
      dataType - the data type
      counterType - the counter type
      units - the units of the value
      Returns:
      the PerfCounter

    • deferEvictions

      public com.ibm.asyncutil.locks.FairAsyncReadWriteLock deferEvictions()
      Returns an AsyncLock used to defer removal of metrics from the registry. Useful when the event ends outside of the reporting interval.

    • registerGauge

      public void registerGauge​(Gauge gauge)
      Adds the Gauge to the global registry
      Parameters:
      gauge - the gauge

    • removeGauge

      public boolean removeGauge​(Gauge gauge)
      Removes the Gauge from the global registry
      Parameters:
      gauge - the gauge
      Returns:
      true if the gauge was removed

    • stream

      public Stream<Metric<?>> stream()
      Returns:
      a Stream of registered metrics

    • find

      public <R,​ A> R find​(Predicate<Metric<?>> predicate, Collector<Metric<?>,​A,​R> collector)
      Finds the group of Metrics that match the given predicate.
      Parameters:
      predicate - a non-interfering, stateless predicate to apply to each element to determine if it should be included
      collector - a path to the desired metric
      Returns:
      the Metric if it exists, otherwise Optional.empty()

    • find

      public Optional<Metric<?>> find​(Metric.MetricPath path)
      Finds the single Metric with the exact given path.
      Parameters:
      path - a path to the desired metric
      Returns:
      the Metric if it exists, otherwise Optional.empty()

    • removeIf

      public void removeIf​(Predicate<Metric<?>> predicate)
      Removes a counter with the given Metric.MetricPath.
      Parameters:
      predicate - a non-interfering, stateless predicate to apply to each element to determine if it should be removed

    • removeMetricsByBase

      public void removeMetricsByBase​(String basePath)
      Removes the set of metrics with the given base path.
      Parameters:
      basePath - the base path of the metrics

    • clear

      public void clear()
      Removes all PerfCounters from the registry