From 2ddd141e3a147a69c03c15cf683b8f3be12e5da0 Mon Sep 17 00:00:00 2001 From: Ivan Trubach Date: Fri, 29 Aug 2025 08:26:29 +0300 Subject: [PATCH] promhttp: implement WithXFromContext in terms of WithXFromRequest This change adds WithLabelFromRequest and WithExemplarFromRequest options and updates FromContext counterparts to be a convenience wrappers for these options. For example, without this change, setting a label based on http.Request.Pattern requires some juggling with context: var ctxHTTPRequestKey = httpRequestContext{} type httpRequestContext struct { *http.Request } func httpPatternFromContext(ctx context.Context) string { r := ctx.Value(ctxHTTPRequestKey).(*httpRequestContext) return r.Pattern } func instrumentHTTPHandler(h http.Handler) http.Handler { h = promhttp.InstrumentHandlerCounter(httpRequestsTotal, h, promhttp.WithLabelFromCtx("handler", httpPatternFromContext), ) return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { var c httpRequestContext ctx := context.WithValue(r.Context(), ctxHTTPRequestKey, &c) r = r.WithContext(ctx) c = httpRequestContext{r} h.ServeHTTP(w, r) }) } promhttp.WithLabelFromRequest allows to access http.Request directly: func instrumentHTTPHandler(h http.Handler) http.Handler { return promhttp.InstrumentHandlerCounter(httpRequestsTotal, h, promhttp.WithLabelFromRequest("handler", func(r *http.Request) string { return r.Pattern }), ) } Signed-off-by: Ivan Trubach --- prometheus/promhttp/instrument_client.go | 12 +++--- prometheus/promhttp/instrument_server.go | 48 ++++++++++++------------ prometheus/promhttp/option.go | 40 ++++++++++++++++---- 3 files changed, 62 insertions(+), 38 deletions(-) diff --git a/prometheus/promhttp/instrument_client.go b/prometheus/promhttp/instrument_client.go index d3482c40c..024857974 100644 --- a/prometheus/promhttp/instrument_client.go +++ b/prometheus/promhttp/instrument_client.go @@ -75,10 +75,10 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou resp, err := next.RoundTrip(r) if err == nil { l := labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...) - for label, resolve := range rtOpts.extraLabelsFromCtx { - l[label] = resolve(resp.Request.Context()) + for label, resolve := range rtOpts.extraLabelsFromRequest { + l[label] = resolve(resp.Request) } - addWithExemplar(counter.With(l), 1, rtOpts.getExemplarFn(r.Context())) + addWithExemplar(counter.With(l), 1, rtOpts.getExemplarFn(r)) } return resp, err } @@ -119,10 +119,10 @@ func InstrumentRoundTripperDuration(obs prometheus.ObserverVec, next http.RoundT resp, err := next.RoundTrip(r) if err == nil { l := labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...) - for label, resolve := range rtOpts.extraLabelsFromCtx { - l[label] = resolve(resp.Request.Context()) + for label, resolve := range rtOpts.extraLabelsFromRequest { + l[label] = resolve(resp.Request) } - observeWithExemplar(obs.With(l), time.Since(start).Seconds(), rtOpts.getExemplarFn(r.Context())) + observeWithExemplar(obs.With(l), time.Since(start).Seconds(), rtOpts.getExemplarFn(r)) } return resp, err } diff --git a/prometheus/promhttp/instrument_server.go b/prometheus/promhttp/instrument_server.go index 9332b0249..29015350a 100644 --- a/prometheus/promhttp/instrument_server.go +++ b/prometheus/promhttp/instrument_server.go @@ -97,10 +97,10 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op next.ServeHTTP(d, r) l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context())) + observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r)) } } @@ -108,10 +108,10 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op now := time.Now() next.ServeHTTP(w, r) l := labels(code, method, r.Method, 0, hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context())) + observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r)) } } @@ -147,10 +147,10 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler, next.ServeHTTP(d, r) l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r.Context())) + addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r)) } } @@ -158,10 +158,10 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler, next.ServeHTTP(w, r) l := labels(code, method, r.Method, 0, hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r.Context())) + addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r)) } } @@ -200,10 +200,10 @@ func InstrumentHandlerTimeToWriteHeader(obs prometheus.ObserverVec, next http.Ha now := time.Now() d := newDelegator(w, func(status int) { l := labels(code, method, r.Method, status, hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context())) + observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r)) }) next.ServeHTTP(d, r) } @@ -244,10 +244,10 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler, size := computeApproximateRequestSize(r) l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r.Context())) + observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r)) } } @@ -256,10 +256,10 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler, size := computeApproximateRequestSize(r) l := labels(code, method, r.Method, 0, hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r.Context())) + observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r)) } } @@ -296,10 +296,10 @@ func InstrumentHandlerResponseSize(obs prometheus.ObserverVec, next http.Handler next.ServeHTTP(d, r) l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...) - for label, resolve := range hOpts.extraLabelsFromCtx { - l[label] = resolve(r.Context()) + for label, resolve := range hOpts.extraLabelsFromRequest { + l[label] = resolve(r) } - observeWithExemplar(obs.With(l), float64(d.Written()), hOpts.getExemplarFn(r.Context())) + observeWithExemplar(obs.With(l), float64(d.Written()), hOpts.getExemplarFn(r)) }) } diff --git a/prometheus/promhttp/option.go b/prometheus/promhttp/option.go index 5d4383aa1..600e065e8 100644 --- a/prometheus/promhttp/option.go +++ b/prometheus/promhttp/option.go @@ -15,6 +15,7 @@ package promhttp import ( "context" + "net/http" "github.com/prometheus/client_golang/prometheus" ) @@ -24,28 +25,31 @@ type Option interface { apply(*options) } +// LabelValueFromRequest is used to compute the label value from request. +type LabelValueFromRequest func(request *http.Request) string + // 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 + extraMethods []string + getExemplarFn func(req *http.Request) prometheus.Labels + extraLabelsFromRequest map[string]LabelValueFromRequest } func defaultOptions() *options { return &options{ - getExemplarFn: func(ctx context.Context) prometheus.Labels { return nil }, - extraLabelsFromCtx: map[string]LabelValueFromCtx{}, + getExemplarFn: func(req *http.Request) prometheus.Labels { return nil }, + extraLabelsFromRequest: map[string]LabelValueFromRequest{}, } } func (o *options) emptyDynamicLabels() prometheus.Labels { labels := prometheus.Labels{} - for label := range o.extraLabelsFromCtx { + for label := range o.extraLabelsFromRequest { labels[label] = "" } @@ -66,12 +70,30 @@ func WithExtraMethods(methods ...string) Option { }) } +// WithExemplarFromRequest allows to inject function that will get exemplar from request 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 WithExemplarFromRequest(getExemplarFn func(req *http.Request) prometheus.Labels) Option { + return optionApplyFunc(func(o *options) { + o.getExemplarFn = getExemplarFn + }) +} + // 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 + o.getExemplarFn = func(req *http.Request) prometheus.Labels { + return getExemplarFn(req.Context()) + } + }) +} + +// WithLabelFromRequest registers a label for dynamic resolution with access to the request. +func WithLabelFromRequest(name string, valueFn LabelValueFromRequest) Option { + return optionApplyFunc(func(o *options) { + o.extraLabelsFromRequest[name] = valueFn }) } @@ -79,6 +101,8 @@ func WithExemplarFromContext(getExemplarFn func(requestCtx context.Context) prom // See the example for ExampleInstrumentHandlerWithLabelResolver for example usage func WithLabelFromCtx(name string, valueFn LabelValueFromCtx) Option { return optionApplyFunc(func(o *options) { - o.extraLabelsFromCtx[name] = valueFn + o.extraLabelsFromRequest[name] = func(req *http.Request) string { + return valueFn(req.Context()) + } }) }