Merge pull request #764 from prometheus/wrap-nil
Ensure that nil registers are treat as a no-op, even when wrapping.
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commit
03575cad4e
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@ -0,0 +1,25 @@
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// Copyright 2020 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package promauto
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import (
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"testing"
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"github.com/prometheus/client_golang/prometheus"
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)
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func TestNil(t *testing.T) {
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// A nil registerer should be treated as a no-op by promauto.
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With(nil).NewCounter(prometheus.CounterOpts{Name: "test"}).Inc()
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}
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@ -28,7 +28,8 @@ import (
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// registered with the wrapped Registerer in a modified way. The modified
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// Collector adds the provided Labels to all Metrics it collects (as
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// ConstLabels). The Metrics collected by the unmodified Collector must not
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// duplicate any of those labels.
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// duplicate any of those labels. Wrapping a nil value is valid, resulting
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// in a no-op Registerer.
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//
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// WrapRegistererWith provides a way to add fixed labels to a subset of
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// Collectors. It should not be used to add fixed labels to all metrics exposed.
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@ -51,6 +52,7 @@ func WrapRegistererWith(labels Labels, reg Registerer) Registerer {
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// Registerer. Collectors registered with the returned Registerer will be
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// registered with the wrapped Registerer in a modified way. The modified
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// Collector adds the provided prefix to the name of all Metrics it collects.
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// Wrapping a nil value is valid, resulting in a no-op Registerer.
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//
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// WrapRegistererWithPrefix is useful to have one place to prefix all metrics of
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// a sub-system. To make this work, register metrics of the sub-system with the
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@ -81,6 +83,9 @@ type wrappingRegisterer struct {
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}
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func (r *wrappingRegisterer) Register(c Collector) error {
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if r.wrappedRegisterer == nil {
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return nil
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}
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return r.wrappedRegisterer.Register(&wrappingCollector{
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wrappedCollector: c,
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prefix: r.prefix,
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@ -89,6 +94,9 @@ func (r *wrappingRegisterer) Register(c Collector) error {
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}
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func (r *wrappingRegisterer) MustRegister(cs ...Collector) {
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if r.wrappedRegisterer == nil {
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return
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}
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for _, c := range cs {
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if err := r.Register(c); err != nil {
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panic(err)
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@ -97,6 +105,9 @@ func (r *wrappingRegisterer) MustRegister(cs ...Collector) {
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}
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func (r *wrappingRegisterer) Unregister(c Collector) bool {
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if r.wrappedRegisterer == nil {
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return false
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}
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return r.wrappedRegisterer.Unregister(&wrappingCollector{
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wrappedCollector: c,
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prefix: r.prefix,
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@ -321,3 +321,12 @@ func TestWrap(t *testing.T) {
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}
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}
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func TestNil(t *testing.T) {
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// A wrapped nil registerer should be treated as a no-op, and not panic.
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c := NewCounter(CounterOpts{Name: "test"})
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err := WrapRegistererWith(Labels{"foo": "bar"}, nil).Register(c)
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if err != nil {
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t.Fatal("registering failed:", err)
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}
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}
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