client_golang/prometheus/promhttp/instrument_server.go

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// Copyright 2017 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 (
"errors"
"net/http"
"strconv"
"strings"
"time"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/client_golang/prometheus"
)
// magicString is used for the hacky label test in checkLabels. Remove once fixed.
const magicString = "zZgWfBxLqvG8kc8IMv3POi2Bb0tZI3vAnBx+gBaFi9FyPzB/CzKUer1yufDa"
// observeWithExemplar is a wrapper for [prometheus.ExemplarAdder.ExemplarObserver],
// which falls back to [prometheus.Observer.Observe] if no labels are provided.
func observeWithExemplar(obs prometheus.Observer, val float64, labels map[string]string) {
if labels == nil {
obs.Observe(val)
return
}
obs.(prometheus.ExemplarObserver).ObserveWithExemplar(val, labels)
}
// addWithExemplar is a wrapper for [prometheus.ExemplarAdder.AddWithExemplar],
// which falls back to [prometheus.Counter.Add] if no labels are provided.
func addWithExemplar(obs prometheus.Counter, val float64, labels map[string]string) {
if labels == nil {
obs.Add(val)
return
}
obs.(prometheus.ExemplarAdder).AddWithExemplar(val, labels)
}
// InstrumentHandlerInFlight is a middleware that wraps the provided
// http.Handler. It sets the provided prometheus.Gauge to the number of
// requests currently handled by the wrapped http.Handler.
//
// See the example for InstrumentHandlerDuration for example usage.
func InstrumentHandlerInFlight(g prometheus.Gauge, next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
g.Inc()
defer g.Dec()
next.ServeHTTP(w, r)
})
}
// InstrumentHandlerDuration is a middleware that wraps the provided
// http.Handler to observe the request duration with the provided ObserverVec.
// The ObserverVec must have valid metric and label names and 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 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 in the ObserverVec is called with the request duration
// in seconds. Partitioning happens by HTTP status code and/or HTTP method if
// the respective instance label names are present in the ObserverVec. For
// unpartitioned observations, use an ObserverVec with zero labels. Note that
// partitioning of Histograms is expensive and should be used judiciously.
//
// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
//
// If the wrapped Handler panics, no values are reported.
//
// Note that this method is only guaranteed to never observe negative durations
// if used with Go1.9+.
func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, opts ...Option) http.HandlerFunc {
hOpts := defaultOptions()
for _, o := range opts {
o.apply(hOpts)
}
// 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) {
now := time.Now()
d := newDelegator(w, nil)
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())
}
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)
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()))
}
}
// InstrumentHandlerCounter is a middleware that wraps the provided http.Handler
// to observe the request result with the provided CounterVec. The CounterVec
// must have valid metric and label names and 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 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. Partitioning of the
// CounterVec happens by HTTP status code and/or HTTP method if the respective
// instance label names are present in the CounterVec. For unpartitioned
// counting, use a CounterVec with zero labels.
//
// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
//
// If the wrapped Handler panics, the Counter is not incremented.
//
// See the example for InstrumentHandlerDuration for example usage.
func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler, opts ...Option) http.HandlerFunc {
hOpts := defaultOptions()
for _, o := range opts {
o.apply(hOpts)
}
// 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)
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)
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()))
}
}
// InstrumentHandlerTimeToWriteHeader is a middleware that wraps the provided
// http.Handler to observe with the provided ObserverVec the request duration
// until the response headers are written. The ObserverVec must have valid
// metric and label names and 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 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 in the
// ObserverVec is called with the request duration in seconds. Partitioning
// happens by HTTP status code and/or HTTP method if the respective instance
// label names are present in the ObserverVec. For unpartitioned observations,
// use an ObserverVec with zero labels. Note that partitioning of Histograms is
// expensive and should be used judiciously.
//
// If the wrapped Handler panics before calling WriteHeader, no value is
// reported.
//
// Note that this method is only guaranteed to never observe negative durations
// if used with Go1.9+.
//
// See the example for InstrumentHandlerDuration for example usage.
func InstrumentHandlerTimeToWriteHeader(obs prometheus.ObserverVec, next http.Handler, opts ...Option) http.HandlerFunc {
hOpts := defaultOptions()
for _, o := range opts {
o.apply(hOpts)
}
// 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) {
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)
}
}
// InstrumentHandlerRequestSize is a middleware that wraps the provided
// http.Handler to observe the request size with the provided ObserverVec. The
// ObserverVec must have valid metric and label names and 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 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 in the ObserverVec is called with the request size in
// bytes. Partitioning happens by HTTP status code and/or HTTP method if the
// respective instance label names are present in the ObserverVec. For
// unpartitioned observations, use an ObserverVec with zero labels. Note that
// partitioning of Histograms is expensive and should be used judiciously.
//
// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
//
// If the wrapped Handler panics, no values are reported.
//
// See the example for InstrumentHandlerDuration for example usage.
func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler, opts ...Option) http.HandlerFunc {
hOpts := defaultOptions()
for _, o := range opts {
o.apply(hOpts)
}
// 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)
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)
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()))
}
}
// InstrumentHandlerResponseSize is a middleware that wraps the provided
// http.Handler to observe the response size with the provided ObserverVec. The
// ObserverVec must have valid metric and label names and 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 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 in the ObserverVec is called with the response size in
// bytes. Partitioning happens by HTTP status code and/or HTTP method if the
// respective instance label names are present in the ObserverVec. For
// unpartitioned observations, use an ObserverVec with zero labels. Note that
// partitioning of Histograms is expensive and should be used judiciously.
//
// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
//
// If the wrapped Handler panics, no values are reported.
//
// See the example for InstrumentHandlerDuration for example usage.
func InstrumentHandlerResponseSize(obs prometheus.ObserverVec, next http.Handler, opts ...Option) http.Handler {
hOpts := defaultOptions()
for _, o := range opts {
o.apply(hOpts)
}
// 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)
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()))
})
}
// checkLabels returns whether the provided Collector has a non-const,
// non-curried label named "code" and/or "method". It panics if the provided
// Collector does not have a Desc or has more than one Desc or its Desc is
// invalid. It also panics if the Collector has any non-const, non-curried
// labels that are not named "code" or "method".
func checkLabels(c prometheus.Collector) (code, method bool) {
// TODO(beorn7): Remove this hacky way to check for instance labels
// once Descriptors can have their dimensionality queried.
var (
desc *prometheus.Desc
m prometheus.Metric
pm dto.Metric
lvs []string
)
// Get the Desc from the Collector.
descc := make(chan *prometheus.Desc, 1)
c.Describe(descc)
select {
case desc = <-descc:
default:
panic("no description provided by collector")
}
select {
case <-descc:
panic("more than one description provided by collector")
default:
}
close(descc)
// Make sure the Collector has a valid Desc by registering it with a
// temporary registry.
prometheus.NewRegistry().MustRegister(c)
// Create a ConstMetric with the Desc. Since we don't know how many
// variable labels there are, try for as long as it needs.
for err := errors.New("dummy"); err != nil; lvs = append(lvs, magicString) {
m, err = prometheus.NewConstMetric(desc, prometheus.UntypedValue, 0, lvs...)
}
// Write out the metric into a proto message and look at the labels.
// If the value is not the magicString, it is a constLabel, which doesn't interest us.
// If the label is curried, it doesn't interest us.
// In all other cases, only "code" or "method" is allowed.
if err := m.Write(&pm); err != nil {
panic("error checking metric for labels")
}
for _, label := range pm.Label {
name, value := label.GetName(), label.GetValue()
if value != magicString || isLabelCurried(c, name) {
continue
}
switch name {
case "code":
code = true
case "method":
method = true
default:
panic("metric partitioned with non-supported labels")
}
}
return
}
func isLabelCurried(c prometheus.Collector, label string) bool {
// This is even hackier than the label test above.
// We essentially try to curry again and see if it works.
// But for that, we need to type-convert to the two
// types we use here, ObserverVec or *CounterVec.
switch v := c.(type) {
case *prometheus.CounterVec:
if _, err := v.CurryWith(prometheus.Labels{label: "dummy"}); err == nil {
return false
}
case prometheus.ObserverVec:
if _, err := v.CurryWith(prometheus.Labels{label: "dummy"}); err == nil {
return false
}
default:
panic("unsupported metric vec type")
}
return true
}
// emptyLabels is a one-time allocation for non-partitioned metrics to avoid
// unnecessary allocations on each request.
var emptyLabels = prometheus.Labels{}
func labels(code, method bool, reqMethod string, status int, extraMethods ...string) prometheus.Labels {
if !(code || method) {
return emptyLabels
}
labels := prometheus.Labels{}
if code {
labels["code"] = sanitizeCode(status)
}
if method {
labels["method"] = sanitizeMethod(reqMethod, extraMethods...)
}
return labels
}
func computeApproximateRequestSize(r *http.Request) int {
s := 0
if r.URL != nil {
s += len(r.URL.String())
}
s += len(r.Method)
s += len(r.Proto)
for name, values := range r.Header {
s += len(name)
for _, value := range values {
s += len(value)
}
}
s += len(r.Host)
// N.B. r.Form and r.MultipartForm are assumed to be included in r.URL.
if r.ContentLength != -1 {
s += int(r.ContentLength)
}
return s
}
// If the wrapped http.Handler has a known method, it will be sanitized and returned.
// Otherwise, "unknown" will be returned. The known method list can be extended
// as needed by using extraMethods parameter.
func sanitizeMethod(m string, extraMethods ...string) string {
// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods for
// the methods chosen as default.
switch m {
case "GET", "get":
return "get"
case "PUT", "put":
return "put"
case "HEAD", "head":
return "head"
case "POST", "post":
return "post"
case "DELETE", "delete":
return "delete"
case "CONNECT", "connect":
return "connect"
case "OPTIONS", "options":
return "options"
case "NOTIFY", "notify":
return "notify"
case "TRACE", "trace":
return "trace"
case "PATCH", "patch":
return "patch"
default:
for _, method := range extraMethods {
if strings.EqualFold(m, method) {
return strings.ToLower(m)
}
}
return "unknown"
}
}
// If the wrapped http.Handler has not set a status code, i.e. the value is
// currently 0, sanitizeCode will return 200, for consistency with behavior in
// the stdlib.
func sanitizeCode(s int) string {
// See for accepted codes https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
switch s {
case 100:
return "100"
case 101:
return "101"
case 200, 0:
return "200"
case 201:
return "201"
case 202:
return "202"
case 203:
return "203"
case 204:
return "204"
case 205:
return "205"
case 206:
return "206"
case 300:
return "300"
case 301:
return "301"
case 302:
return "302"
case 304:
return "304"
case 305:
return "305"
case 307:
return "307"
case 400:
return "400"
case 401:
return "401"
case 402:
return "402"
case 403:
return "403"
case 404:
return "404"
case 405:
return "405"
case 406:
return "406"
case 407:
return "407"
case 408:
return "408"
case 409:
return "409"
case 410:
return "410"
case 411:
return "411"
case 412:
return "412"
case 413:
return "413"
case 414:
return "414"
case 415:
return "415"
case 416:
return "416"
case 417:
return "417"
case 418:
return "418"
case 500:
return "500"
case 501:
return "501"
case 502:
return "502"
case 503:
return "503"
case 504:
return "504"
case 505:
return "505"
case 428:
return "428"
case 429:
return "429"
case 431:
return "431"
case 511:
return "511"
default:
if s >= 100 && s <= 599 {
return strconv.Itoa(s)
}
return "unknown"
}
}