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Add possibility to dynamically get label values for http instrumentation (#1066) 

Signed-off-by: Quentin Devos <4972091+Okhoshi@users.noreply.github.com>

Signed-off-by: Quentin Devos <4972091+Okhoshi@users.noreply.github.com>
This commit is contained in:
Quentin D 2023-01-19 11:19:08 +01:00 committed by GitHub
parent fc5f34ceda
commit fcdc3ec54a
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 212 additions and 76 deletions
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3
examples/simple/main.go
View File

@ -16,10 +16,11 @@ package main
import (
"flag"
"github.com/prometheus/client_golang/prometheus/collectors"
"log"
"net/http"
"github.com/prometheus/client_golang/prometheus/collectors"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)

26
prometheus/promhttp/instrument_client.go
View File

@ -68,16 +68,17 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
o.apply(rtOpts)
}
code, method := checkLabels(counter)
// Curry the counter with dynamic labels before checking the remaining labels.
code, method := checkLabels(counter.MustCurryWith(rtOpts.emptyDynamicLabels()))
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...)),
1,
rtOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...)
for label, resolve := range rtOpts.extraLabelsFromCtx {
l[label] = resolve(resp.Request.Context())
}
addWithExemplar(counter.With(l), 1, rtOpts.getExemplarFn(r.Context()))
}
return resp, err
}
@ -110,17 +111,18 @@ func InstrumentRoundTripperDuration(obs prometheus.ObserverVec, next http.RoundT
o.apply(rtOpts)
}
code, method := checkLabels(obs)
// Curry the observer with dynamic labels before checking the remaining labels.
code, method := checkLabels(obs.MustCurryWith(rtOpts.emptyDynamicLabels()))
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...)),
time.Since(start).Seconds(),
rtOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...)
for label, resolve := range rtOpts.extraLabelsFromCtx {
l[label] = resolve(resp.Request.Context())
}
observeWithExemplar(obs.With(l), time.Since(start).Seconds(), rtOpts.getExemplarFn(r.Context()))
}
return resp, err
}

101
prometheus/promhttp/instrument_server.go
View File

@ -87,7 +87,8 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op
o.apply(hOpts)
}
code, method := checkLabels(obs)
// Curry the observer with dynamic labels before checking the remaining labels.
code, method := checkLabels(obs.MustCurryWith(hOpts.emptyDynamicLabels()))
if code {
return func(w http.ResponseWriter, r *http.Request) {
@ -95,23 +96,22 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op
d := newDelegator(w, nil)
next.ServeHTTP(d, r)
observeWithExemplar(
obs.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
time.Since(now).Seconds(),
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
}
}
return func(w http.ResponseWriter, r *http.Request) {
now := time.Now()
next.ServeHTTP(w, r)
observeWithExemplar(
obs.With(labels(code, method, r.Method, 0, hOpts.extraMethods...)),
time.Since(now).Seconds(),
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, 0, hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
}
}
@ -138,28 +138,30 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler,
o.apply(hOpts)
}
code, method := checkLabels(counter)
// Curry the counter with dynamic labels before checking the remaining labels.
code, method := checkLabels(counter.MustCurryWith(hOpts.emptyDynamicLabels()))
if code {
return func(w http.ResponseWriter, r *http.Request) {
d := newDelegator(w, nil)
next.ServeHTTP(d, r)
addWithExemplar(
counter.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
1,
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r.Context()))
}
}
return func(w http.ResponseWriter, r *http.Request) {
next.ServeHTTP(w, r)
addWithExemplar(
counter.With(labels(code, method, r.Method, 0, hOpts.extraMethods...)),
1,
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, 0, hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r.Context()))
}
}
@ -191,16 +193,17 @@ func InstrumentHandlerTimeToWriteHeader(obs prometheus.ObserverVec, next http.Ha
o.apply(hOpts)
}
code, method := checkLabels(obs)
// Curry the observer with dynamic labels before checking the remaining labels.
code, method := checkLabels(obs.MustCurryWith(hOpts.emptyDynamicLabels()))
return func(w http.ResponseWriter, r *http.Request) {
now := time.Now()
d := newDelegator(w, func(status int) {
observeWithExemplar(
obs.With(labels(code, method, r.Method, status, hOpts.extraMethods...)),
time.Since(now).Seconds(),
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, status, hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
})
next.ServeHTTP(d, r)
}
@ -231,28 +234,32 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler,
o.apply(hOpts)
}
code, method := checkLabels(obs)
// Curry the observer with dynamic labels before checking the remaining labels.
code, method := checkLabels(obs.MustCurryWith(hOpts.emptyDynamicLabels()))
if code {
return func(w http.ResponseWriter, r *http.Request) {
d := newDelegator(w, nil)
next.ServeHTTP(d, r)
size := computeApproximateRequestSize(r)
observeWithExemplar(
obs.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
float64(size),
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r.Context()))
}
}
return func(w http.ResponseWriter, r *http.Request) {
next.ServeHTTP(w, r)
size := computeApproximateRequestSize(r)
observeWithExemplar(
obs.With(labels(code, method, r.Method, 0, hOpts.extraMethods...)),
float64(size),
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, 0, hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r.Context()))
}
}
@ -281,16 +288,18 @@ func InstrumentHandlerResponseSize(obs prometheus.ObserverVec, next http.Handler
o.apply(hOpts)
}
code, method := checkLabels(obs)
// Curry the observer with dynamic labels before checking the remaining labels.
code, method := checkLabels(obs.MustCurryWith(hOpts.emptyDynamicLabels()))
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
d := newDelegator(w, nil)
next.ServeHTTP(d, r)
observeWithExemplar(
obs.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
float64(d.Written()),
hOpts.getExemplarFn(r.Context()),
)
l := labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)
for label, resolve := range hOpts.extraLabelsFromCtx {
l[label] = resolve(r.Context())
}
observeWithExemplar(obs.With(l), float64(d.Written()), hOpts.getExemplarFn(r.Context()))
})
}

50
prometheus/promhttp/instrument_server_test.go
View File

@ -30,6 +30,7 @@ func TestLabelCheck(t *testing.T) {
varLabels []string
constLabels []string
curriedLabels []string
dynamicLabels []string
ok bool
}{
"empty": {
@ -60,12 +61,14 @@ func TestLabelCheck(t *testing.T) {
varLabels: []string{"code", "method"},
constLabels: []string{"foo", "bar"},
curriedLabels: []string{"dings", "bums"},
dynamicLabels: []string{"dyn", "amics"},
ok: true,
},
"all labels used with an invalid const label name": {
varLabels: []string{"code", "method"},
constLabels: []string{"in-valid", "bar"},
curriedLabels: []string{"dings", "bums"},
dynamicLabels: []string{"dyn", "amics"},
ok: false,
},
"unsupported var label": {
@ -98,6 +101,18 @@ func TestLabelCheck(t *testing.T) {
curriedLabels: []string{"method"},
ok: true,
},
"supported label as const and dynamic": {
varLabels: []string{},
constLabels: []string{"code"},
dynamicLabels: []string{"method"},
ok: true,
},
"supported label as curried and dynamic": {
varLabels: []string{},
curriedLabels: []string{"code"},
dynamicLabels: []string{"method"},
ok: true,
},
"supported label as const and curry with unsupported as var": {
varLabels: []string{"foo"},
constLabels: []string{"code"},
@ -116,6 +131,7 @@ func TestLabelCheck(t *testing.T) {
varLabels: []string{"code", "method"},
constLabels: []string{"foo", "bar"},
curriedLabels: []string{"dings", "bums"},
dynamicLabels: []string{"dyn", "amics"},
ok: false,
},
}
@ -130,26 +146,39 @@ func TestLabelCheck(t *testing.T) {
for _, l := range sc.constLabels {
constLabels[l] = "dummy"
}
c := prometheus.NewCounterVec(
prometheus.CounterOpts{
labelNames := append(append(sc.varLabels, sc.curriedLabels...), sc.dynamicLabels...)
c := prometheus.V2.NewCounterVec(
prometheus.CounterVecOpts{
CounterOpts: prometheus.CounterOpts{
Name: metricName,
Help: "c help",
ConstLabels: constLabels,
},
append(sc.varLabels, sc.curriedLabels...),
VariableLabels: prometheus.UnconstrainedLabels(labelNames),
},
)
o := prometheus.ObserverVec(prometheus.NewHistogramVec(
prometheus.HistogramOpts{
o := prometheus.ObserverVec(prometheus.V2.NewHistogramVec(
prometheus.HistogramVecOpts{
HistogramOpts: prometheus.HistogramOpts{
Name: metricName,
Help: "c help",
ConstLabels: constLabels,
},
append(sc.varLabels, sc.curriedLabels...),
VariableLabels: prometheus.UnconstrainedLabels(labelNames),
},
))
for _, l := range sc.curriedLabels {
c = c.MustCurryWith(prometheus.Labels{l: "dummy"})
o = o.MustCurryWith(prometheus.Labels{l: "dummy"})
}
opts := []Option{}
for _, l := range sc.dynamicLabels {
opts = append(opts, WithLabelFromCtx(l,
func(_ context.Context) string {
return "foo"
},
))
}
func() {
defer func() {
@ -161,7 +190,7 @@ func TestLabelCheck(t *testing.T) {
t.Error("expected panic")
}
}()
InstrumentHandlerCounter(c, nil)
InstrumentHandlerCounter(c, nil, opts...)
}()
func() {
defer func() {
@ -173,7 +202,7 @@ func TestLabelCheck(t *testing.T) {
t.Error("expected panic")
}
}()
InstrumentHandlerDuration(o, nil)
InstrumentHandlerDuration(o, nil, opts...)
}()
if sc.ok {
// Test if wantCode and wantMethod were detected correctly.
@ -186,6 +215,11 @@ func TestLabelCheck(t *testing.T) {
wantMethod = true
}
}
// Curry the dynamic labels since this is done normally behind the scenes for the check
for _, l := range sc.dynamicLabels {
c = c.MustCurryWith(prometheus.Labels{l: "dummy"})
o = o.MustCurryWith(prometheus.Labels{l: "dummy"})
}
gotCode, gotMethod := checkLabels(c)
if gotCode != wantCode {
t.Errorf("wanted code=%t for counter, got code=%t", wantCode, gotCode)

28
prometheus/promhttp/option.go
View File

@ -24,14 +24,32 @@ 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 }}
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)
@ -56,3 +74,11 @@ func WithExemplarFromContext(getExemplarFn func(requestCtx context.Context) prom
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
})
}

64
prometheus/promhttp/option_test.go
View File

@ -14,12 +14,19 @@
package promhttp
import (
"context"
"log"
"net/http"
"github.com/prometheus/client_golang/prometheus"
)
type key int
const (
CtxResolverKey key = iota
)
func ExampleInstrumentHandlerWithExtraMethods() {
counter := prometheus.NewCounterVec(
prometheus.CounterOpts{
@ -62,3 +69,60 @@ func ExampleInstrumentHandlerWithExtraMethods() {
log.Fatal(err)
}
}
func ExampleInstrumentHandlerWithLabelResolver() {
counter := prometheus.NewCounterVec(
prometheus.CounterOpts{
Name: "api_requests_total",
Help: "A counter for requests to the wrapped handler.",
},
[]string{"code", "method", "myheader"},
)
// duration is partitioned by the HTTP method, handler and request header
// value. It uses custom buckets based on the expected request duration.
// Beware to not have too high cardinality on the values of header. You
// always should sanitize external inputs.
duration := prometheus.NewHistogramVec(
prometheus.HistogramOpts{
Name: "request_duration_seconds",
Help: "A histogram of latencies for requests.",
Buckets: []float64{.25, .5, 1, 2.5, 5, 10},
},
[]string{"handler", "method", "myheader"},
)
// Create the handlers that will be wrapped by the middleware.
pullHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Write([]byte("Pull"))
})
// Specify additional HTTP methods to be added to the label allow list.
opts := WithLabelFromCtx("myheader",
func(ctx context.Context) string {
return ctx.Value(CtxResolverKey).(string)
},
)
// Instrument the handlers with all the metrics, injecting the "handler"
// label by currying.
pullChain := InstrumentHandlerDuration(duration.MustCurryWith(prometheus.Labels{"handler": "pull"}),
InstrumentHandlerCounter(counter, pullHandler, opts),
opts,
)
middleware := func(next http.HandlerFunc) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
ctx := context.WithValue(r.Context(), CtxResolverKey, r.Header.Get("x-my-header"))
next(w, r.WithContext(ctx))
}
}
http.Handle("/metrics", Handler())
http.Handle("/pull", middleware(pullChain))
if err := http.ListenAndServe(":3000", nil); err != nil {
log.Fatal(err)
}
}