Improve CollectAndCount
Now that we have also added CollectAndLint and GatherAndLint, I thought we should bring CollectAndCount in line. So: - Add GatherAndCount. - Add filtering by metric name. - Add tests. Minor wart: CollectAndCount should now return `(int, error)`, but that would be a breaking change as the current version just returns `int`. I decided to let the new version panic when it should return an error. An error is anyway very unlikely, so the biggest annoyance here is really just the inconsistency. Signed-off-by: beorn7 <beorn@grafana.com>
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@ -112,31 +112,43 @@ func ToFloat64(c prometheus.Collector) float64 {
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panic(fmt.Errorf("collected a non-gauge/counter/untyped metric: %s", pb))
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}
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// CollectAndCount collects all Metrics from the provided Collector and returns their number.
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//
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// This can be used to assert the number of metrics collected by a given collector after certain operations.
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//
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// This function is only for testing purposes, and even for testing, other approaches
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// are often more appropriate (see this package's documentation).
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func CollectAndCount(c prometheus.Collector) int {
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var (
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mCount int
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mChan = make(chan prometheus.Metric)
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done = make(chan struct{})
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)
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// CollectAndCount registers the provided Collector with a newly created
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// pedantic Registry. It then calls GatherAndCount with that Registry and with
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// the provided metricNames. In the unlikely case that the registration or the
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// gathering fails, this function panics. (This is inconsistent with the other
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// CollectAnd… functions in this package and has historical reasons. Changing
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// the function signature would be a breaking change and will therefore only
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// happen with the next major version bump.)
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func CollectAndCount(c prometheus.Collector, metricNames ...string) int {
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reg := prometheus.NewPedanticRegistry()
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if err := reg.Register(c); err != nil {
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panic(fmt.Errorf("registering collector failed: %s", err))
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}
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result, err := GatherAndCount(reg, metricNames...)
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if err != nil {
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panic(err)
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}
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return result
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}
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go func() {
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for range mChan {
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mCount++
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}
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close(done)
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}()
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// GatherAndCount gathers all metrics from the provided Gatherer and counts
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// them. It returns the number of metric children in all gathered metric
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// families together. If any metricNames are provided, only metrics with those
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// names are counted.
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func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) {
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got, err := g.Gather()
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if err != nil {
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return 0, fmt.Errorf("gathering metrics failed: %s", err)
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}
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if metricNames != nil {
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got = filterMetrics(got, metricNames)
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}
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c.Collect(mChan)
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close(mChan)
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<-done
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return mCount
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result := 0
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for _, mf := range got {
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result += len(mf.GetMetric())
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}
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return result, nil
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}
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// CollectAndCompare registers the provided Collector with a newly created
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@ -306,3 +306,30 @@ some_total{label1="value1"} 1
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t.Errorf("Expected\n%#+v\nGot:\n%#+v", expectedError, err.Error())
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}
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}
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func TestCollectAndCount(t *testing.T) {
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c := prometheus.NewCounterVec(
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prometheus.CounterOpts{
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Name: "some_total",
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Help: "A value that represents a counter.",
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},
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[]string{"foo"},
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)
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if got, want := CollectAndCount(c), 0; got != want {
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t.Errorf("unexpected metric count, got %d, want %d", got, want)
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}
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c.WithLabelValues("bar")
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if got, want := CollectAndCount(c), 1; got != want {
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t.Errorf("unexpected metric count, got %d, want %d", got, want)
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}
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c.WithLabelValues("baz")
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if got, want := CollectAndCount(c), 2; got != want {
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t.Errorf("unexpected metric count, got %d, want %d", got, want)
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}
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if got, want := CollectAndCount(c, "some_total"), 2; got != want {
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t.Errorf("unexpected metric count, got %d, want %d", got, want)
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}
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if got, want := CollectAndCount(c, "some_other_total"), 0; got != want {
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t.Errorf("unexpected metric count, got %d, want %d", got, want)
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}
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}
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