Apache Storm version 1.2 introduced a new metrics system for reporting internal statistics (e.g. acked, failed, emitted, transferred, disruptor queue metrics, etc.) as well as a new API for user defined metrics.

User Defined Metrics

To allow users to define custom metrics, the following methods have been added to the TopologyContext class, an instance of which is passed to spout’s open() method and bolt’s prepare() method:

public Timer registerTimer(String name)

public Histogram registerHistogram(String name)

public Meter registerMeter(String name)

public Counter registerCounter(String name)

public Gauge registerGauge(String name, Gauge gauge)

Each of these methods takes a name parameter that acts as an identifier. When metrics are registered, Storm will add additional information such as hostname, port, topology ID, etc. to form a unique metric identifier. For example, if we register a metric named myCounter as follows:

    Counter myCounter = topologyContext.registerCounter("myCounter");

   storm.topology.{topology ID}.{hostname}.{component ID}.{task ID}.{worker port}-myCounter

The additional information allows for the unique identification of metrics for component instances across the cluster.

Important Note: In order to ensure metric names can be reliably parsed, any . characters in name components will be replaced with an underscore (_) character. For example, the hostname storm.example.com will appear as storm_example_com in the metric name. This character substitution *is not applied to the user-supplied name parameter.

Example: Tuple Counter Bolt

The following example is a simple bolt implementation that will report the running total up tuples received by a bolt:

public class TupleCountingBolt extends BaseRichBolt {
    private Counter tupleCounter;
    @Override
    public void prepare(Map stormConf, TopologyContext context, OutputCollector collector) {
        this.tupleCounter = context.registerCounter("tupleCount");
    }

    @Override
    public void execute(Tuple input) {
        this.tupleCounter.inc();
    }
}

Metric Reporter Configuration

For metrics to be useful they must be reported, in other words sent somewhere where they can be consumed and analyzed. That can be as simple as writing them to a log file, sending them to a time series database, or exposing them via JMX.

Metrics reporters are configured in the storm.yaml file. By default, Storm will collect metrics but not “report” or send the collected metrics anywhere. To enable metrics reporting, add a storm.metrics.reporters section to storm.yaml and configure one or more reporters.

The following example configuration sets up two reporters: a Graphite Reporter and a Console Reporter:

storm.metrics.reporters:
  # Graphite Reporter
  - class: "org.apache.storm.metrics2.reporters.GraphiteStormReporter"
    daemons:
        - "supervisor"
        - "nimbus"
        - "worker"
    report.period: 60
    report.period.units: "SECONDS"
    graphite.host: "localhost"
    graphite.port: 2003

  # Console Reporter
  - class: "org.apache.storm.metrics2.reporters.ConsoleStormReporter"
    daemons:
        - "worker"
    report.period: 10
    report.period.units: "SECONDS"
    filter:
        class: "org.apache.storm.metrics2.filters.RegexFilter"
        expression: ".*my_component.*emitted.*"

Each reporter section begins with a class parameter representing the fully-qualified class name of the reporter implementation. The daemons section determines which daemons the reporter will apply to (in the example Graphite Reporter is configured to report metrics from all Storm daemons, while the Console reporter will only report worker and topology metrics).

Many reporter implementations are scheduled, meaning they report metrics at regular intervals. The reporting interval is determined by the report.period and report.period.units parameters.

Reporters can also be configured with an optional filter that determines which metrics get reported. Storm includes the org.apache.storm.metrics2.filters.RegexFilter filter which uses a regular expression to determine which metrics get reported. Custom filters can be created by implementing the org.apache.storm.metrics2.filters.StormMetricFilter interface:

public interface StormMetricsFilter extends MetricFilter {

    /**
     * Called after the filter is instantiated.
     * @param config A map of the properties from the 'filter' section of the reporter configuration.
     */
    void prepare(Map<String, Object> config);
    
   /**
    *  Returns true if the given metric should be reported.
    */
    boolean matches(String name, Metric metric);

}