Package io.prometheus.client

Class Histogram

  • All Implemented Interfaces:
    Collector.Describable
    public class Histogram
extends SimpleCollector<Histogram.Child>
implements Collector.Describable
    Histogram metric, to track distributions of events.

    Example of uses for Histograms include:

    • Response latency
    • Request size

    Note: Each bucket is one timeseries. Many buckets and/or many dimensions with labels can produce large amount of time series, that may cause performance problems.

    The default buckets are intended to cover a typical web/rpc request from milliseconds to seconds.

    Example Histograms: 

     
   class YourClass {
     static final Histogram requestLatency = Histogram.build()
         .name("requests_latency_seconds").help("Request latency in seconds.").register();

     void processRequest(Request req) {
        Histogram.Timer requestTimer = requestLatency.startTimer();
        try {
          // Your code here.
        } finally {
          requestTimer.observeDuration();
        }
     }

     // Or if using Java 8 lambdas.
     void processRequestLambda(Request req) {
        requestLatency.time(() -> {
          // Your code here.
        });
     }
   }

    You can choose your own buckets: 

     
     static final Histogram requestLatency = Histogram.build()
         .buckets(.01, .02, .03, .04)
         .name("requests_latency_seconds").help("Request latency in seconds.").register();
    linearBuckets and exponentialBuckets offer easy ways to set common bucket patterns.