AssertJ support for Prometheus Metrics

This library provides AssertJ support for Prometheus Java Client metrics, which simplifies testing your own (Java) exporters or own (Java) application natively exposing metrics.

Download

Available on Maven Central (GAV: de.m3y.prometheus.assertj:assertj-prometheus:VERSION):

<dependency>
    <groupId>de.m3y.prometheus.assertj</groupId>
    <artifactId>assertj-prometheus</artifactId>
    <version>VERSION</version>
    <scope>test</scope>
</dependency>

Examples

A basic example for VersionInfoExports:

VersionInfoExports versionInfoExports = new VersionInfoExports();

// Verify jvm_info
MetricFamilySamples mfs = MetricFamilySamplesUtils.getMetricFamilySamples(
        versionInfoExports.collect(), "jvm");
assertThat(mfs)
        .hasTypeOfInfo()
        .hasSampleLabelNames("vendor", "runtime", "version")
        .hasSampleValue(
                labelValues(
                        System.getProperty("java.runtime.name", "unknown"),
                        System.getProperty("java.vm.vendor", "unknown"),
                        System.getProperty("java.runtime.version", "unknown")
                ));

For further examples, have a look at the tests.

Helpers

Helpers for fetching a single MFS:

Collector.MetricFamilySamples mfs;

// From default registry CollectorRegistry.defaultRegistry
mfs = MetricFamilySamplesUtils.getMetricFamilySamples("my_metric");

// From specific registry
mfs = MetricFamilySamplesUtils.getMetricFamilySamples( CollectorRegistry.defaultRegistry, "my_metric");

// From collector aka exporter
VersionInfoExports versionInfoExports = new VersionInfoExports();
mfs = MetricFamilySamplesUtils.getMetricFamilySamples(versionInfoExports.collect(), "jvm");

Info

Example for Info:

Info info = Info.build().name("testInfo").help("help")
        .labelNames("version", "vendor")
        .create().register();
...
Collector.MetricFamilySamples mfs = MetricFamilySamplesUtils.getMetricFamilySamples("testInfo");
assertThat(mfs)
        .hasType(INFO)
        .hasTypeOfInfo()
        .hasSampleSize(1)
        .hasSampleValue("A", "B"); // Checks if label values exist -
                                   // typical values are your build info version 

Counter or Gauge

Example for a Gauge or Counter:

Collector.MetricFamilySamples mfs = MetricFamilySamplesUtils.getMetricFamilySamples("my_metric");
assertThat(mfs)
        .hasTypeOfGauge() // For a Counter: .hasTypeOfCounter()
        .hasSampleLabelNames("job_type", "app_name", "status")
        .hasSampleValue(
                labelValues("A", "B", "C"),
                10d
        )
        .hasSampleValue(
                labelValues("X", "Y", "Z"),
                da -> da.isCloseTo(10.0, withinPercentage(10d)) // AssertJ double asserts with 10% tolerance
        );

Summary

Example for a Summary with sum, count and quantiles:

Collector.MetricFamilySamples mfs = MetricFamilySamplesUtils.getMetricFamilySamples("my_metric");
assertThat(mfs)
        .hasSampleSize(12)
        .hasSampleLabelNames("label_a")
        .hasTypeOfSummary() // Required for following, summary specific asserts
        .hasSampleCountValue(labelValues("value_a"), 2)
        .hasSampleSumValue(labelValues("value_a"), 40)
        .hasSampleValue(0.5 /* Quantile */, 10)
        .hasSampleValue(0.9 /* Quantile */, 20)
        ...

Histogram

Example for a Histogram with sum, count and buckets:

Collector.MetricFamilySamples mfs = MetricFamilySamplesUtils.getMetricFamilySamples("my_metric");
assertThat(mfs)
        .hasSampleSize(12)
        .hasSampleLabelNames("label_a")
        .hasTypeOfHistogram() // Required for following, histogram specific asserts
        .hasSampleCountValue(labelValues("value_a"), 2)
        .hasSampleSumValue(labelValues("value_a"), 40)
        .hasSampleCountValue(labelValues("value_b"), 2)
        .hasSampleSumValue(labelValues("value_b"), 40)
        .hasSampleBucketValue(labelValues("value_a"), 10, 1) // Histogram bucket assertions
        ...
        .hasSampleBucketValue(labelValues("value_b"), Double.POSITIVE_INFINITY, 2)

Building

mvn clean install

Requirements

• JDK 8+

License and Copyright

Licensed under Apache 2.0 License

Copyright 2018-2024 Marcel May and project contributors.