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avaje-metric-core

Please read the main documentation at: http://avaje-metrics.github.io

Maven dependency

    <dependency>
      <groupId>io.avaje</groupId>
      <artifactId>avaje-metrics</artifactId>
      <version>9.2</version>
    </dependency>

License - Apache 2

Published under Apache Software License 2.0, see LICENSE

MetricRegistry

A MetricRegistry holds the metrics like timers, gauges etc.

MetricRegistry registry = Metrics.createRegistry();

// obtain timers, counters, gauges etc
Timer timer = registry.timer("my.timer");
Counter counter = registry.counter("my.count");

Metrics & default registry

There is default MetricRegistry. Creating metrics via Metrics creates metrics attached to the default registry.

// obtain the default MetricRegistry
MetricRegistry defaultRegistry = Metrics.registry();
// timer registered with the default MetricRegistry
Timer timer = Metrics.timer("my.timer");

Counter

A Counter holds a single long value that is incremented

Counter counter = registry.counter("my.count");

counter.inc();
counter.inc(42);

Meter

A Meter is used to represent events that have a value such as bytes sent, bytes received, lines read etc.

Meter meter = registry.meter("my.meter");

meter.addEvent(42);
meter.addEvent(44);
meter.addEvent(46);

Gauge

Gauges are used to measure something that supplies a value. Creating a Gauge takes either a LongSupplier or a DoubleSupplier.

Gauges are used for JVM Memory metrics and Garbage collection. Although application can obtain values from a Gauge typically we register the gauge and the value is obtained when the metrics are reported.

registry.gauge("my.gauge0", myLongSupplier );
registry.gauge("my.gauge1", myDoubleSupplier );

There are incrementing wrappers that can be applied to the LongSupplier of DoubleSupplier to use for the case when the gauge only increments and we wish to report the change.

// wrap via incrementing()
GaugeLong myIncrementing = GaugeLong.incrementing(myLongSupplier);

registry.gauge("my.gauge", myIncrementing);

Timer

A Timer measures the time on an event in microseconds. It provides count, total time in micros, mean time in micros, max time in micros.

Timers can be obtained and used via code or via @Timed enhancement. We can also apply timers on "All non-private methods of Spring Beans" or "All non-private methods of Avaje Inject Beans"

@Timed

Timers can be added by putting @Timed on a class. Then enhancement will add timers to all non-private methods on that class. We use @NotTimed to not have a method timed.

Using Timer programmatically

Obtain a Timer from the MetricRegistry or via Metrics.timer(...) which uses the default registry.

Timer metric = Metrics.timer("test.runnable");

Time Runnable

The Timer can take a runnable like:

Timer timer = Metrics.timer("test.runnable");

// using runnable
timer.time( //* ... runnable */ );

Time using start nanos

long startNanos = System.nanoTime();

// do something we want to time ...
timer.add(startNanos);

This is an efficient way to time events with no extra object allocation.

The time is the difference between startNanos and when that is added to the timer.

Time using startEvent

Event event = timer.startEvent();
// do something we want to time ...
event.end();