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- // Copyright 2022 The Prometheus Authors
- // Licensed under the Apache License, Version 2.0 (the "License");
- // you may not use this file except in compliance with the License.
- // You may obtain a copy of the License at
- //
- // http://www.apache.org/licenses/LICENSE-2.0
- //
- // Unless required by applicable law or agreed to in writing, software
- // distributed under the License is distributed on an "AS IS" BASIS,
- // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- // See the License for the specific language governing permissions and
- // limitations under the License.
-
- package promhttp
-
- import (
- "context"
-
- "github.com/prometheus/client_golang/prometheus"
- )
-
- // Option are used to configure both handler (middleware) or round tripper.
- type Option interface {
- apply(*options)
- }
-
- // LabelValueFromCtx are used to compute the label value from request context.
- // Context can be filled with values from request through middleware.
- type LabelValueFromCtx func(ctx context.Context) string
-
- // options store options for both a handler or round tripper.
- type options struct {
- extraMethods []string
- getExemplarFn func(requestCtx context.Context) prometheus.Labels
- extraLabelsFromCtx map[string]LabelValueFromCtx
- }
-
- func defaultOptions() *options {
- return &options{
- getExemplarFn: func(ctx context.Context) prometheus.Labels { return nil },
- extraLabelsFromCtx: map[string]LabelValueFromCtx{},
- }
- }
-
- func (o *options) emptyDynamicLabels() prometheus.Labels {
- labels := prometheus.Labels{}
-
- for label := range o.extraLabelsFromCtx {
- labels[label] = ""
- }
-
- return labels
- }
-
- type optionApplyFunc func(*options)
-
- func (o optionApplyFunc) apply(opt *options) { o(opt) }
-
- // WithExtraMethods adds additional HTTP methods to the list of allowed methods.
- // See https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods for the default list.
- //
- // See the example for ExampleInstrumentHandlerWithExtraMethods for example usage.
- func WithExtraMethods(methods ...string) Option {
- return optionApplyFunc(func(o *options) {
- o.extraMethods = methods
- })
- }
-
- // WithExemplarFromContext allows to inject function that will get exemplar from context that will be put to counter and histogram metrics.
- // If the function returns nil labels or the metric does not support exemplars, no exemplar will be added (noop), but
- // metric will continue to observe/increment.
- func WithExemplarFromContext(getExemplarFn func(requestCtx context.Context) prometheus.Labels) Option {
- return optionApplyFunc(func(o *options) {
- o.getExemplarFn = getExemplarFn
- })
- }
-
- // WithLabelFromCtx registers a label for dynamic resolution with access to context.
- // See the example for ExampleInstrumentHandlerWithLabelResolver for example usage
- func WithLabelFromCtx(name string, valueFn LabelValueFromCtx) Option {
- return optionApplyFunc(func(o *options) {
- o.extraLabelsFromCtx[name] = valueFn
- })
- }
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