client_golang/prometheus/http.go

550 lines
16 KiB
Go

// Copyright 2014 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 prometheus
import (
"bufio"
"compress/gzip"
"fmt"
"io"
"net"
"net/http"
"strconv"
"strings"
"time"
"github.com/prometheus/common/expfmt"
)
const (
contentTypeHeader = "Content-Type"
contentLengthHeader = "Content-Length"
contentEncodingHeader = "Content-Encoding"
acceptEncodingHeader = "Accept-Encoding"
)
// Handler returns an HTTP handler for the DefaultRegistry. It is
// already instrumented with InstrumentHandler (using "prometheus" as handler
// name).
//
// Please note the issues described in the doc comment of InstrumentHandler. You
// might want to consider using UninstrumentedHandler instead. In fact, the
// instrumentation of the handler is DEPRECATED. In future versions of this
// package, the Handler function will return an uninstrumented handler, and the
// UninstrumentedHandler function will be removed.
//
// The returned Handler is using the same HandlerOpts as the Handler returned by
// UninstrumentedHandler. See there for details.
func Handler() http.Handler {
return InstrumentHandler("prometheus", UninstrumentedHandler())
}
// UninstrumentedHandler returns an HTTP handler for the DefaultRegistry. The
// Handler uses the default HandlerOpts, i.e. report the first error as an HTTP
// error, no error logging, and compression if requested by the client.
//
// If you want to create a Handler for the DefaultRegistry with different
// HandlerOpts, create it with HandlerFor with the DefaultRegistry and your
// desired HandlerOpts.
//
// Note that in future versions of this package, UninstrumentedHandler will be
// replaced by Handler (which will then return an uninstrumented handler, see
// there for details).
func UninstrumentedHandler() http.Handler {
return HandlerFor(DefaultRegistry, HandlerOpts{})
}
// HandlerFor returns an http.Handler for the provided registry. The behavior ef
// the Handler is defined by the provided HandlerOpts. The Handler is NOT
// instrumented with InstrumentHandler.
func HandlerFor(r Registry, opts HandlerOpts) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
mfs, err := r.Collect()
if err != nil {
if opts.ErrorLog != nil {
opts.ErrorLog.Println("error collecting metrics:", err)
}
switch opts.ErrorHandling {
case PanicOnError:
panic(err)
case ContinueOnError:
if len(mfs) == 0 {
http.Error(w, "No metrics collected, last error:\n\n"+err.Error(), http.StatusInternalServerError)
return
}
case HTTPErrorOnError:
http.Error(w, "An error has occurred during metrics collection:\n\n"+err.Error(), http.StatusInternalServerError)
return
}
}
contentType := expfmt.Negotiate(req.Header)
buf := getBuf()
defer giveBuf(buf)
writer, encoding := decorateWriter(req, buf, opts.DisableCompression)
enc := expfmt.NewEncoder(writer, contentType)
var lastErr error
for _, mf := range mfs {
if err := enc.Encode(mf); err != nil {
lastErr = err
if opts.ErrorLog != nil {
opts.ErrorLog.Println("error encoding metric family:", err)
}
switch opts.ErrorHandling {
case PanicOnError:
panic(err)
case ContinueOnError:
// Handled later.
case HTTPErrorOnError:
http.Error(w, "An error has occurred during metrics encoding:\n\n"+err.Error(), http.StatusInternalServerError)
return
}
}
}
if closer, ok := writer.(io.Closer); ok {
closer.Close()
}
if lastErr != nil && buf.Len() == 0 {
http.Error(w, "No metrics encoded, last error:\n\n"+err.Error(), http.StatusInternalServerError)
return
}
header := w.Header()
header.Set(contentTypeHeader, string(contentType))
header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
if encoding != "" {
header.Set(contentEncodingHeader, encoding)
}
w.Write(buf.Bytes())
// TODO(beorn7): Consider streaming serving of metrics.
})
}
// HandlerErrorHandling defines how a Handler serving metrics will handle
// errors.
type HandlerErrorHandling int
// These constants cause handlers serving metrics to behave as described if
// errors are encountered.
const (
// Serve an HTTP status code 500 upon the first error
// encountered. Report the error message in the body.
HTTPErrorOnError HandlerErrorHandling = iota
// Ignore errors and try to serve as many metrics as possible. However,
// if no metrics can be served, serve an HTTP status code 500 and the
// last error message in the body. Only use this in deliberate "best
// effort" metrics collection scenarios. It is recommended to at least
// log errors (by providing an ErrorLog in HandlerOpts) to not mask
// errors completely.
ContinueOnError
// Panic upon the first error encountered (useful for "crash only" apps).
PanicOnError
)
// Logger is the minimal interface HandlerOpts needs for logging. Note that
// log.Logger from the standard library implements this interface, and it is
// easy to implement by custom loggers, if they don't do so already anyway.
type Logger interface {
Println(v ...interface{})
}
// HandlerOpts specifies options how to serve metrics via an http.Handler. The
// zero value of HandlerOpts is a reasonable default.
type HandlerOpts struct {
// ErrorLog specifies an optional logger for errors collecting and
// serving metrics. If nil, errors are not logged at all.
ErrorLog Logger
// ErrorHandling defines how errors are handled. Note that errors are
// logged regardless of the configured ErrorHandling provided ErrorLog
// is not nil.
ErrorHandling HandlerErrorHandling
// If DisableCompression is true, the handler will never compress the
// response, even if requested by the client.
DisableCompression bool
}
// decorateWriter wraps a writer to handle gzip compression if requested. It
// returns the decorated writer and the appropriate "Content-Encoding" header
// (which is empty if no compression is enabled).
func decorateWriter(request *http.Request, writer io.Writer, compressionDisabled bool) (io.Writer, string) {
if compressionDisabled {
return writer, ""
}
header := request.Header.Get(acceptEncodingHeader)
parts := strings.Split(header, ",")
for _, part := range parts {
part := strings.TrimSpace(part)
if part == "gzip" || strings.HasPrefix(part, "gzip;") {
return gzip.NewWriter(writer), "gzip"
}
}
return writer, ""
}
var instLabels = []string{"method", "code"}
type nower interface {
Now() time.Time
}
type nowFunc func() time.Time
func (n nowFunc) Now() time.Time {
return n()
}
var now nower = nowFunc(func() time.Time {
return time.Now()
})
func nowSeries(t ...time.Time) nower {
return nowFunc(func() time.Time {
defer func() {
t = t[1:]
}()
return t[0]
})
}
// InstrumentHandler wraps the given HTTP handler for instrumentation. It
// registers four metric collectors (if not already done) and reports HTTP
// metrics to the (newly or already) registered collectors: http_requests_total
// (CounterVec), http_request_duration_microseconds (Summary),
// http_request_size_bytes (Summary), http_response_size_bytes (Summary). Each
// has a constant label named "handler" with the provided handlerName as
// value. http_requests_total is a metric vector partitioned by HTTP method
// (label name "method") and HTTP status code (label name "code").
//
// Note that InstrumentHandler has several issues:
//
// - It uses Summaries rather than Histograms. Summaries are not useful if
// aggregation across multiple instances is required.
//
// - It uses microseconds as unit, which is deprecated and should be replaced by
// seconds.
//
// - The size of the request is calculated in a separate goroutine. Since this
// calculator requires access to the request header, it creates a race with
// any writes to the header performed during request handling.
// httputil.ReverseProxy is a prominent example for a handler
// performing such writes.
//
// Upcoming versions of this package will provide ways of instrumenting HTTP
// handlers that are more flexible and have fewer issues. Consider this function
// DEPRECATED and prefer direct instrumentation in the meantime.
func InstrumentHandler(handlerName string, handler http.Handler) http.HandlerFunc {
return InstrumentHandlerFunc(handlerName, handler.ServeHTTP)
}
// InstrumentHandlerFunc wraps the given function for instrumentation. It
// otherwise works in the same way as InstrumentHandler (and shares the same
// issues).
func InstrumentHandlerFunc(handlerName string, handlerFunc func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
return InstrumentHandlerFuncWithOpts(
SummaryOpts{
Subsystem: "http",
ConstLabels: Labels{"handler": handlerName},
},
handlerFunc,
)
}
// InstrumentHandlerWithOpts works like InstrumentHandler (and shares the same
// issues) but provides more flexibility (at the cost of a more complex call
// syntax). As InstrumentHandler, this function registers four metric
// collectors, but it uses the provided SummaryOpts to create them. However, the
// fields "Name" and "Help" in the SummaryOpts are ignored. "Name" is replaced
// by "requests_total", "request_duration_microseconds", "request_size_bytes",
// and "response_size_bytes", respectively. "Help" is replaced by an appropriate
// help string. The names of the variable labels of the http_requests_total
// CounterVec are "method" (get, post, etc.), and "code" (HTTP status code).
//
// If InstrumentHandlerWithOpts is called as follows, it mimics exactly the
// behavior of InstrumentHandler:
//
// prometheus.InstrumentHandlerWithOpts(
// prometheus.SummaryOpts{
// Subsystem: "http",
// ConstLabels: prometheus.Labels{"handler": handlerName},
// },
// handler,
// )
//
// Technical detail: "requests_total" is a CounterVec, not a SummaryVec, so it
// cannot use SummaryOpts. Instead, a CounterOpts struct is created internally,
// and all its fields are set to the equally named fields in the provided
// SummaryOpts.
func InstrumentHandlerWithOpts(opts SummaryOpts, handler http.Handler) http.HandlerFunc {
return InstrumentHandlerFuncWithOpts(opts, handler.ServeHTTP)
}
// InstrumentHandlerFuncWithOpts works like InstrumentHandlerFunc (and shares
// the same issues) but provides more flexibility (at the cost of a more complex
// call syntax). See InstrumentHandlerWithOpts for details how the provided
// SummaryOpts are used.
func InstrumentHandlerFuncWithOpts(opts SummaryOpts, handlerFunc func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
reqCnt := NewCounterVec(
CounterOpts{
Namespace: opts.Namespace,
Subsystem: opts.Subsystem,
Name: "requests_total",
Help: "Total number of HTTP requests made.",
ConstLabels: opts.ConstLabels,
},
instLabels,
)
opts.Name = "request_duration_microseconds"
opts.Help = "The HTTP request latencies in microseconds."
reqDur := NewSummary(opts)
opts.Name = "request_size_bytes"
opts.Help = "The HTTP request sizes in bytes."
reqSz := NewSummary(opts)
opts.Name = "response_size_bytes"
opts.Help = "The HTTP response sizes in bytes."
resSz := NewSummary(opts)
regReqCnt := MustRegisterOrGet(reqCnt).(*CounterVec)
regReqDur := MustRegisterOrGet(reqDur).(Summary)
regReqSz := MustRegisterOrGet(reqSz).(Summary)
regResSz := MustRegisterOrGet(resSz).(Summary)
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
now := time.Now()
delegate := &responseWriterDelegator{ResponseWriter: w}
out := make(chan int)
urlLen := 0
if r.URL != nil {
urlLen = len(r.URL.String())
}
go computeApproximateRequestSize(r, out, urlLen)
_, cn := w.(http.CloseNotifier)
_, fl := w.(http.Flusher)
_, hj := w.(http.Hijacker)
_, rf := w.(io.ReaderFrom)
var rw http.ResponseWriter
if cn && fl && hj && rf {
rw = &fancyResponseWriterDelegator{delegate}
} else {
rw = delegate
}
handlerFunc(rw, r)
elapsed := float64(time.Since(now)) / float64(time.Microsecond)
method := sanitizeMethod(r.Method)
code := sanitizeCode(delegate.status)
regReqCnt.WithLabelValues(method, code).Inc()
regReqDur.Observe(elapsed)
regResSz.Observe(float64(delegate.written))
regReqSz.Observe(float64(<-out))
})
}
func computeApproximateRequestSize(r *http.Request, out chan int, s int) {
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)
}
out <- s
}
type responseWriterDelegator struct {
http.ResponseWriter
handler, method string
status int
written int64
wroteHeader bool
}
func (r *responseWriterDelegator) WriteHeader(code int) {
r.status = code
r.wroteHeader = true
r.ResponseWriter.WriteHeader(code)
}
func (r *responseWriterDelegator) Write(b []byte) (int, error) {
if !r.wroteHeader {
r.WriteHeader(http.StatusOK)
}
n, err := r.ResponseWriter.Write(b)
r.written += int64(n)
return n, err
}
type fancyResponseWriterDelegator struct {
*responseWriterDelegator
}
func (f *fancyResponseWriterDelegator) CloseNotify() <-chan bool {
return f.ResponseWriter.(http.CloseNotifier).CloseNotify()
}
func (f *fancyResponseWriterDelegator) Flush() {
f.ResponseWriter.(http.Flusher).Flush()
}
func (f *fancyResponseWriterDelegator) Hijack() (net.Conn, *bufio.ReadWriter, error) {
return f.ResponseWriter.(http.Hijacker).Hijack()
}
func (f *fancyResponseWriterDelegator) ReadFrom(r io.Reader) (int64, error) {
if !f.wroteHeader {
f.WriteHeader(http.StatusOK)
}
n, err := f.ResponseWriter.(io.ReaderFrom).ReadFrom(r)
f.written += n
return n, err
}
func sanitizeMethod(m string) string {
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"
default:
return strings.ToLower(m)
}
}
func sanitizeCode(s int) string {
switch s {
case 100:
return "100"
case 101:
return "101"
case 200:
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:
return strconv.Itoa(s)
}
}