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expose a request path label (prototype) #1139

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31 changes: 31 additions & 0 deletions prometheus/promhttp/context.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
// 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"

type _PathKey string

var requestPathKey _PathKey

func WithRequestPath(ctx context.Context, path string) context.Context {
return context.WithValue(ctx, requestPathKey, path)
}

func pathFromContext(ctx context.Context) string {
if value, ok := ctx.Value(requestPathKey).(string); ok {
return value
}
return "*"
}
16 changes: 9 additions & 7 deletions prometheus/promhttp/instrument_client.go
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Expand Up @@ -48,7 +48,7 @@ func InstrumentRoundTripperInFlight(gauge prometheus.Gauge, next http.RoundTripp
// InstrumentRoundTripperCounter is a middleware that wraps the provided
// http.RoundTripper to observe the request result with the provided CounterVec.
// The CounterVec must have zero, one, or two non-const non-curried labels. For
// those, the only allowed label names are "code" and "method". The function
// those, the only allowed label names are "code", "method" and "path". The function
// panics otherwise. For the "method" label a predefined default label value set
// is used to filter given values. Values besides predefined values will count
// as `unknown` method.`WithExtraMethods` can be used to add more
Expand All @@ -60,6 +60,7 @@ func InstrumentRoundTripperInFlight(gauge prometheus.Gauge, next http.RoundTripp
// is not incremented.
//
// Use with WithExemplarFromContext to instrument the exemplars on the counter of requests.
// Use with WithRequestPath to associate the request path with the context.
//
// See the example for ExampleInstrumentRoundTripperDuration for example usage.
func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.RoundTripper, opts ...Option) RoundTripperFunc {
Expand All @@ -68,13 +69,13 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
o.apply(rtOpts)
}

code, method := checkLabels(counter)
code, method, path := checkLabels(counter)

return func(r *http.Request) (*http.Response, error) {
resp, err := next.RoundTrip(r)
if err == nil {
addWithExemplar(
counter.With(labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...)),
counter.With(labels(code, method, path, r.Method, resp.StatusCode, rtOpts.getRequestPathFn(r), rtOpts.extraMethods...)),
1,
rtOpts.getExemplarFn(r.Context()),
)
Expand All @@ -86,8 +87,8 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
// InstrumentRoundTripperDuration is a middleware that wraps the provided
// http.RoundTripper to observe the request duration with the provided
// ObserverVec. The ObserverVec must have zero, one, or two non-const
// non-curried labels. For those, the only allowed label names are "code" and
// "method". The function panics otherwise. For the "method" label a predefined
// non-curried labels. For those, the only allowed label names are "code", "method"
// and "path". The function panics otherwise. For the "method" label a predefined
// default label value set is used to filter given values. Values besides
// predefined values will count as `unknown` method. `WithExtraMethods`
// can be used to add more methods to the set. The Observe method of the Observer
Expand All @@ -101,6 +102,7 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
// reported.
//
// Use with WithExemplarFromContext to instrument the exemplars on the duration histograms.
// Use with WithRequestPath to associate the request path with the context.
//
// Note that this method is only guaranteed to never observe negative durations
// if used with Go1.9+.
Expand All @@ -110,14 +112,14 @@ func InstrumentRoundTripperDuration(obs prometheus.ObserverVec, next http.RoundT
o.apply(rtOpts)
}

code, method := checkLabels(obs)
code, method, path := checkLabels(obs)

return func(r *http.Request) (*http.Response, error) {
start := time.Now()
resp, err := next.RoundTrip(r)
if err == nil {
observeWithExemplar(
obs.With(labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...)),
obs.With(labels(code, method, path, r.Method, resp.StatusCode, rtOpts.getRequestPathFn(r), rtOpts.extraMethods...)),
time.Since(start).Seconds(),
rtOpts.getExemplarFn(r.Context()),
)
Expand Down
16 changes: 11 additions & 5 deletions prometheus/promhttp/instrument_client_test.go
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Expand Up @@ -47,7 +47,7 @@ func makeInstrumentedClient(opts ...Option) (*http.Client, *prometheus.Registry)
Name: "client_api_requests_total",
Help: "A counter for requests from the wrapped client.",
},
[]string{"code", "method"},
[]string{"code", "method", "path"},
)

dnsLatencyVec := prometheus.NewHistogramVec(
Expand Down Expand Up @@ -228,8 +228,9 @@ func TestClientMiddlewareAPI_WithRequestContext(t *testing.T) {
t.Fatalf("%v", err)
}

ctx := WithRequestPath(context.Background(), "/home")
// Set a context with a long timeout.
ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
defer cancel()
req = req.WithContext(ctx)

Expand All @@ -256,7 +257,7 @@ func TestClientMiddlewareAPI_WithRequestContext(t *testing.T) {
expected := `
# HELP client_api_requests_total A counter for requests from the wrapped client.
# TYPE client_api_requests_total counter
client_api_requests_total{code="200",method="get"} 1
client_api_requests_total{code="200",method="get",path="/home"} 1
`

if err := testutil.GatherAndCompare(reg, strings.NewReader(expected),
Expand Down Expand Up @@ -310,7 +311,7 @@ func ExampleInstrumentRoundTripperDuration() {
Name: "client_api_requests_total",
Help: "A counter for requests from the wrapped client.",
},
[]string{"code", "method"},
[]string{"code", "method", "path"},
)

// dnsLatencyVec uses custom buckets based on expected dns durations.
Expand Down Expand Up @@ -381,7 +382,12 @@ func ExampleInstrumentRoundTripperDuration() {
// Set the RoundTripper on our client.
client.Transport = roundTripper

resp, err := client.Get("http://google.com")
ctx := WithRequestPath(context.Background(), "/")
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://google.com", nil)
if err != nil {
log.Printf("error: %v", err)
}
resp, err := client.Do(req)
if err != nil {
log.Printf("error: %v", err)
}
Expand Down
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