Function TestBatchHistogram

prometheus/go_collector_latest_test.go:151–231

(t *testing.T)

var sink interface{}

func TestBatchHistogram(t *testing.T) {
	goMetrics := collectGoMetrics(t, internal.GoCollectorOptions{
		RuntimeMetricRules: []internal.GoCollectorRule{
			{Matcher: regexp.MustCompile("/.*")},
		},
	})

	var mhist Metric
	for _, m := range goMetrics {
		if m.Desc().fqName == "go_gc_heap_allocs_by_size_bytes" {
			mhist = m
			break
		}
	}
	if mhist == nil {
		t.Fatal("failed to find metric to test")
	}
	hist, ok := mhist.(*batchHistogram)
	if !ok {
		t.Fatal("found metric is not a runtime/metrics histogram")
	}

	// Make a bunch of allocations then do another collection.
	//
	// The runtime/metrics API tries to reuse memory where possible,
	// so make sure that we didn't hang on to any of that memory in
	// hist.
	countsCopy := make([]uint64, len(hist.counts))
	copy(countsCopy, hist.counts)
	for i := 0; i < 100; i++ {
		sink = make([]byte, 128)
	}

	collectGoMetrics(t, defaultGoCollectorOptions())
	for i, v := range hist.counts {
		if v != countsCopy[i] {
			t.Error("counts changed during new collection")
			break
		}
	}

	// Get the runtime/metrics copy.
	s := []metrics.Sample{
		{Name: "/gc/heap/allocs-by-size:bytes"},
	}
	metrics.Read(s)
	rmHist := s[0].Value.Float64Histogram()
	wantBuckets := internal.RuntimeMetricsBucketsForUnit(rmHist.Buckets, "bytes")
	// runtime/metrics histograms always have a +Inf bucket and are lower
	// bound inclusive. In contrast, we have an implicit +Inf bucket and
	// are upper bound inclusive, so we can chop off the first bucket
	// (since the conversion to upper bound inclusive will shift all buckets
	// down one index) and the +Inf for the last bucket.
	wantBuckets = wantBuckets[1 : len(wantBuckets)-1]

	// Check to make sure the output proto makes sense.
	pb := &dto.Metric{}
	hist.Write(pb)