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459 lines
14 KiB
459 lines
14 KiB
// Copyright 2017 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package promhttp
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import (
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"errors"
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"net/http"
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"strconv"
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"strings"
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"time"
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dto "github.com/prometheus/client_model/go"
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"github.com/prometheus/client_golang/prometheus"
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)
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// magicString is used for the hacky label test in checkLabels. Remove once fixed.
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const magicString = "zZgWfBxLqvG8kc8IMv3POi2Bb0tZI3vAnBx+gBaFi9FyPzB/CzKUer1yufDa"
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// InstrumentHandlerInFlight is a middleware that wraps the provided
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// http.Handler. It sets the provided prometheus.Gauge to the number of
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// requests currently handled by the wrapped http.Handler.
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//
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// See the example for InstrumentHandlerDuration for example usage.
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func InstrumentHandlerInFlight(g prometheus.Gauge, next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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g.Inc()
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defer g.Dec()
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next.ServeHTTP(w, r)
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})
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}
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// InstrumentHandlerDuration is a middleware that wraps the provided
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// http.Handler to observe the request duration with the provided ObserverVec.
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// The ObserverVec must have valid metric and label names and must have zero,
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// one, or two non-const non-curried labels. For those, the only allowed label
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// names are "code" and "method". The function panics otherwise. The Observe
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// method of the Observer in the ObserverVec is called with the request duration
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// in seconds. Partitioning happens by HTTP status code and/or HTTP method if
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// the respective instance label names are present in the ObserverVec. For
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// unpartitioned observations, use an ObserverVec with zero labels. Note that
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// partitioning of Histograms is expensive and should be used judiciously.
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//
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// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
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//
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// If the wrapped Handler panics, no values are reported.
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//
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// Note that this method is only guaranteed to never observe negative durations
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// if used with Go1.9+.
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func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler) http.HandlerFunc {
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code, method := checkLabels(obs)
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if code {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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now := time.Now()
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d := newDelegator(w, nil)
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next.ServeHTTP(d, r)
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obs.With(labels(code, method, r.Method, d.Status())).Observe(time.Since(now).Seconds())
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})
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}
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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now := time.Now()
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next.ServeHTTP(w, r)
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obs.With(labels(code, method, r.Method, 0)).Observe(time.Since(now).Seconds())
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})
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}
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// InstrumentHandlerCounter is a middleware that wraps the provided http.Handler
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// to observe the request result with the provided CounterVec. The CounterVec
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// must have valid metric and label names and must have zero, one, or two
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// non-const non-curried labels. For those, the only allowed label names are
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// "code" and "method". The function panics otherwise. Partitioning of the
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// CounterVec happens by HTTP status code and/or HTTP method if the respective
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// instance label names are present in the CounterVec. For unpartitioned
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// counting, use a CounterVec with zero labels.
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//
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// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
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//
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// If the wrapped Handler panics, the Counter is not incremented.
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//
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// See the example for InstrumentHandlerDuration for example usage.
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func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler) http.HandlerFunc {
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code, method := checkLabels(counter)
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if code {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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d := newDelegator(w, nil)
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next.ServeHTTP(d, r)
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counter.With(labels(code, method, r.Method, d.Status())).Inc()
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})
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}
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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next.ServeHTTP(w, r)
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counter.With(labels(code, method, r.Method, 0)).Inc()
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})
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}
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// InstrumentHandlerTimeToWriteHeader is a middleware that wraps the provided
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// http.Handler to observe with the provided ObserverVec the request duration
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// until the response headers are written. The ObserverVec must have valid
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// metric and label names and must have zero, one, or two non-const non-curried
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// labels. For those, the only allowed label names are "code" and "method". The
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// function panics otherwise. The Observe method of the Observer in the
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// ObserverVec is called with the request duration in seconds. Partitioning
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// happens by HTTP status code and/or HTTP method if the respective instance
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// label names are present in the ObserverVec. For unpartitioned observations,
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// use an ObserverVec with zero labels. Note that partitioning of Histograms is
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// expensive and should be used judiciously.
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//
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// If the wrapped Handler panics before calling WriteHeader, no value is
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// reported.
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//
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// Note that this method is only guaranteed to never observe negative durations
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// if used with Go1.9+.
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//
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// See the example for InstrumentHandlerDuration for example usage.
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func InstrumentHandlerTimeToWriteHeader(obs prometheus.ObserverVec, next http.Handler) http.HandlerFunc {
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code, method := checkLabels(obs)
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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now := time.Now()
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d := newDelegator(w, func(status int) {
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obs.With(labels(code, method, r.Method, status)).Observe(time.Since(now).Seconds())
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})
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next.ServeHTTP(d, r)
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})
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}
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// InstrumentHandlerRequestSize is a middleware that wraps the provided
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// http.Handler to observe the request size with the provided ObserverVec. The
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// ObserverVec must have valid metric and label names and must have zero, one,
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// or two non-const non-curried labels. For those, the only allowed label names
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// are "code" and "method". The function panics otherwise. The Observe method of
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// the Observer in the ObserverVec is called with the request size in
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// bytes. Partitioning happens by HTTP status code and/or HTTP method if the
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// respective instance label names are present in the ObserverVec. For
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// unpartitioned observations, use an ObserverVec with zero labels. Note that
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// partitioning of Histograms is expensive and should be used judiciously.
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//
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// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
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//
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// If the wrapped Handler panics, no values are reported.
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//
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// See the example for InstrumentHandlerDuration for example usage.
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func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler) http.HandlerFunc {
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code, method := checkLabels(obs)
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if code {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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d := newDelegator(w, nil)
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next.ServeHTTP(d, r)
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size := computeApproximateRequestSize(r)
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obs.With(labels(code, method, r.Method, d.Status())).Observe(float64(size))
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})
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}
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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next.ServeHTTP(w, r)
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size := computeApproximateRequestSize(r)
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obs.With(labels(code, method, r.Method, 0)).Observe(float64(size))
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})
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}
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// InstrumentHandlerResponseSize is a middleware that wraps the provided
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// http.Handler to observe the response size with the provided ObserverVec. The
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// ObserverVec must have valid metric and label names and must have zero, one,
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// or two non-const non-curried labels. For those, the only allowed label names
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// are "code" and "method". The function panics otherwise. The Observe method of
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// the Observer in the ObserverVec is called with the response size in
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// bytes. Partitioning happens by HTTP status code and/or HTTP method if the
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// respective instance label names are present in the ObserverVec. For
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// unpartitioned observations, use an ObserverVec with zero labels. Note that
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// partitioning of Histograms is expensive and should be used judiciously.
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//
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// If the wrapped Handler does not set a status code, a status code of 200 is assumed.
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//
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// If the wrapped Handler panics, no values are reported.
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//
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// See the example for InstrumentHandlerDuration for example usage.
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func InstrumentHandlerResponseSize(obs prometheus.ObserverVec, next http.Handler) http.Handler {
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code, method := checkLabels(obs)
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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d := newDelegator(w, nil)
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next.ServeHTTP(d, r)
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obs.With(labels(code, method, r.Method, d.Status())).Observe(float64(d.Written()))
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})
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}
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// checkLabels returns whether the provided Collector has a non-const,
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// non-curried label named "code" and/or "method". It panics if the provided
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// Collector does not have a Desc or has more than one Desc or its Desc is
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// invalid. It also panics if the Collector has any non-const, non-curried
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// labels that are not named "code" or "method".
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func checkLabels(c prometheus.Collector) (code bool, method bool) {
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// TODO(beorn7): Remove this hacky way to check for instance labels
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// once Descriptors can have their dimensionality queried.
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var (
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desc *prometheus.Desc
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m prometheus.Metric
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pm dto.Metric
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lvs []string
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)
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// Get the Desc from the Collector.
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descc := make(chan *prometheus.Desc, 1)
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c.Describe(descc)
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select {
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case desc = <-descc:
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default:
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panic("no description provided by collector")
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}
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select {
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case <-descc:
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panic("more than one description provided by collector")
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default:
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}
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close(descc)
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// Make sure the Collector has a valid Desc by registering it with a
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// temporary registry.
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prometheus.NewRegistry().MustRegister(c)
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// Create a ConstMetric with the Desc. Since we don't know how many
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// variable labels there are, try for as long as it needs.
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for err := errors.New("dummy"); err != nil; lvs = append(lvs, magicString) {
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m, err = prometheus.NewConstMetric(desc, prometheus.UntypedValue, 0, lvs...)
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}
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// Write out the metric into a proto message and look at the labels.
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// If the value is not the magicString, it is a constLabel, which doesn't interest us.
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// If the label is curried, it doesn't interest us.
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// In all other cases, only "code" or "method" is allowed.
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if err := m.Write(&pm); err != nil {
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panic("error checking metric for labels")
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}
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for _, label := range pm.Label {
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name, value := label.GetName(), label.GetValue()
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if value != magicString || isLabelCurried(c, name) {
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continue
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}
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switch name {
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case "code":
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code = true
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case "method":
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method = true
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default:
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panic("metric partitioned with non-supported labels")
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}
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}
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return
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}
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func isLabelCurried(c prometheus.Collector, label string) bool {
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// This is even hackier than the label test above.
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// We essentially try to curry again and see if it works.
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// But for that, we need to type-convert to the two
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// types we use here, ObserverVec or *CounterVec.
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switch v := c.(type) {
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case *prometheus.CounterVec:
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if _, err := v.CurryWith(prometheus.Labels{label: "dummy"}); err == nil {
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return false
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}
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case prometheus.ObserverVec:
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if _, err := v.CurryWith(prometheus.Labels{label: "dummy"}); err == nil {
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return false
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}
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default:
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panic("unsupported metric vec type")
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}
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return true
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}
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// emptyLabels is a one-time allocation for non-partitioned metrics to avoid
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// unnecessary allocations on each request.
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var emptyLabels = prometheus.Labels{}
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func labels(code, method bool, reqMethod string, status int) prometheus.Labels {
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if !(code || method) {
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return emptyLabels
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}
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labels := prometheus.Labels{}
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if code {
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labels["code"] = sanitizeCode(status)
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}
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if method {
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labels["method"] = sanitizeMethod(reqMethod)
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}
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return labels
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}
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func computeApproximateRequestSize(r *http.Request) int {
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s := 0
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if r.URL != nil {
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s += len(r.URL.String())
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}
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s += len(r.Method)
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s += len(r.Proto)
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for name, values := range r.Header {
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s += len(name)
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for _, value := range values {
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s += len(value)
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}
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}
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s += len(r.Host)
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// N.B. r.Form and r.MultipartForm are assumed to be included in r.URL.
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if r.ContentLength != -1 {
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s += int(r.ContentLength)
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}
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return s
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}
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func sanitizeMethod(m string) string {
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switch m {
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case "GET", "get":
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return "get"
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case "PUT", "put":
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return "put"
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case "HEAD", "head":
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return "head"
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case "POST", "post":
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return "post"
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case "DELETE", "delete":
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return "delete"
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case "CONNECT", "connect":
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return "connect"
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case "OPTIONS", "options":
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return "options"
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case "NOTIFY", "notify":
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return "notify"
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default:
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return strings.ToLower(m)
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}
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}
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// If the wrapped http.Handler has not set a status code, i.e. the value is
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// currently 0, santizeCode will return 200, for consistency with behavior in
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// the stdlib.
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func sanitizeCode(s int) string {
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switch s {
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case 100:
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return "100"
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case 101:
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return "101"
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case 200, 0:
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return "200"
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case 201:
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return "201"
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case 202:
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return "202"
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case 203:
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return "203"
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case 204:
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return "204"
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case 205:
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return "205"
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case 206:
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return "206"
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case 300:
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return "300"
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case 301:
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return "301"
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case 302:
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return "302"
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case 304:
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return "304"
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case 305:
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return "305"
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case 307:
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return "307"
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case 400:
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return "400"
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case 401:
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return "401"
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case 402:
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return "402"
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case 403:
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return "403"
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case 404:
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return "404"
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case 405:
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return "405"
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case 406:
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return "406"
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case 407:
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return "407"
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case 408:
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return "408"
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case 409:
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return "409"
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case 410:
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return "410"
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case 411:
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return "411"
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case 412:
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return "412"
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case 413:
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return "413"
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case 414:
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return "414"
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case 415:
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return "415"
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case 416:
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return "416"
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case 417:
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return "417"
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case 418:
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return "418"
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case 500:
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return "500"
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case 501:
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return "501"
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case 502:
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return "502"
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case 503:
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return "503"
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case 504:
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return "504"
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case 505:
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return "505"
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case 428:
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return "428"
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case 429:
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return "429"
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case 431:
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return "431"
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case 511:
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return "511"
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default:
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return strconv.Itoa(s)
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}
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}
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