Review feedback: add comment and tests for WrapRegistererWith.

Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>
This commit is contained in:
Tom Wilkie 2020-06-04 11:51:51 +01:00
parent 614377c550
commit 9c8ba1f945
3 changed files with 15 additions and 6 deletions

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@ -19,9 +19,7 @@ import (
"github.com/prometheus/client_golang/prometheus"
)
func TestWrapNil(t *testing.T) {
// A nil registerer should be treated as a no-op by promauto, even when wrapped.
registerer := prometheus.WrapRegistererWith(prometheus.Labels{"foo": "bar"}, nil)
c := With(registerer).NewCounter(prometheus.CounterOpts{Name: "test"})
c.Inc()
func TestNil(t *testing.T) {
// A nil registerer should be treated as a no-op by promauto.
With(nil).NewCounter(prometheus.CounterOpts{Name: "test"}).Inc()
}

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@ -28,7 +28,8 @@ import (
// registered with the wrapped Registerer in a modified way. The modified
// Collector adds the provided Labels to all Metrics it collects (as
// ConstLabels). The Metrics collected by the unmodified Collector must not
// duplicate any of those labels.
// duplicate any of those labels. Wrapping a nil value is valid, resulting
// in a no-op Registerer.
//
// WrapRegistererWith provides a way to add fixed labels to a subset of
// Collectors. It should not be used to add fixed labels to all metrics exposed.
@ -51,6 +52,7 @@ func WrapRegistererWith(labels Labels, reg Registerer) Registerer {
// Registerer. Collectors registered with the returned Registerer will be
// registered with the wrapped Registerer in a modified way. The modified
// Collector adds the provided prefix to the name of all Metrics it collects.
// Wrapping a nil value is valid, resulting in a no-op Registerer.
//
// WrapRegistererWithPrefix is useful to have one place to prefix all metrics of
// a sub-system. To make this work, register metrics of the sub-system with the

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@ -321,3 +321,12 @@ func TestWrap(t *testing.T) {
}
}
func TestNil(t *testing.T) {
// A wrapped nil registerer should be treated as a no-op, and not panic.
c := NewCounter(CounterOpts{Name: "test"})
err := WrapRegistererWith(Labels{"foo": "bar"}, nil).Register(c)
if err != nil {
t.Fatal("registering failed:", err)
}
}