382 lines
9.6 KiB
Go
382 lines
9.6 KiB
Go
// Copyright 2014 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 prometheus
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import (
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"bufio"
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"io"
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"net"
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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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)
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var instLabels = []string{"method", "code"}
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type nower interface {
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Now() time.Time
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}
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type nowFunc func() time.Time
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func (n nowFunc) Now() time.Time {
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return n()
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}
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var now nower = nowFunc(func() time.Time {
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return time.Now()
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})
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func nowSeries(t ...time.Time) nower {
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return nowFunc(func() time.Time {
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defer func() {
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t = t[1:]
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}()
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return t[0]
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})
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}
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// InstrumentHandler wraps the given HTTP handler for instrumentation. It
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// registers four metric collectors (if not already done) and reports HTTP
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// metrics to the (newly or already) registered collectors: http_requests_total
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// (CounterVec), http_request_duration_microseconds (Summary),
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// http_request_size_bytes (Summary), http_response_size_bytes (Summary). Each
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// has a constant label named "handler" with the provided handlerName as
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// value. http_requests_total is a metric vector partitioned by HTTP method
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// (label name "method") and HTTP status code (label name "code").
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//
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// Note that InstrumentHandler has several issues:
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//
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// - It uses Summaries rather than Histograms. Summaries are not useful if
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// aggregation accross multiple instances is required.
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//
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// - It uses microseconds as unit, which is deprecated and should be reploced by
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// seconds.
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//
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// - The size of the request is calculated in a separate goroutine. Since this
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// calculatior requires access to the request header, it creates a race with
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// any writes to the header performed during request handling.
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// httputil.ReverseProxy is a prominent example for a handler
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// performing such writes.
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//
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// Upcoming versions of this package will provide ways of instrumenting HTTP
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// handlers that are more flexible and have fewer issues. Consider this function
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// DEPRECATED and prefer direct instrumentation in the meantime.
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func InstrumentHandler(handlerName string, handler http.Handler) http.HandlerFunc {
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return InstrumentHandlerFunc(handlerName, handler.ServeHTTP)
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}
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// InstrumentHandlerFunc wraps the given function for instrumentation. It
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// otherwise works in the same way as InstrumentHandler (and shares the same
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// issues).
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func InstrumentHandlerFunc(handlerName string, handlerFunc func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
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return InstrumentHandlerFuncWithOpts(
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SummaryOpts{
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Subsystem: "http",
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ConstLabels: Labels{"handler": handlerName},
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},
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handlerFunc,
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)
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}
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// InstrumentHandlerWithOpts works like InstrumentHandler (and shares the same
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// issues) but provides more flexibility (at the cost of a more complex call
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// syntax). As InstrumentHandler, this function registers four metric
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// collectors, but it uses the provided SummaryOpts to create them. However, the
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// fields "Name" and "Help" in the SummaryOpts are ignored. "Name" is replaced
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// by "requests_total", "request_duration_microseconds", "request_size_bytes",
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// and "response_size_bytes", respectively. "Help" is replaced by an appropriate
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// help string. The names of the variable labels of the http_requests_total
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// CounterVec are "method" (get, post, etc.), and "code" (HTTP status code).
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//
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// If InstrumentHandlerWithOpts is called as follows, it mimics exactly the
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// behavior of InstrumentHandler:
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//
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// prometheus.InstrumentHandlerWithOpts(
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// prometheus.SummaryOpts{
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// Subsystem: "http",
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// ConstLabels: prometheus.Labels{"handler": handlerName},
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// },
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// handler,
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// )
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//
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// Technical detail: "requests_total" is a CounterVec, not a SummaryVec, so it
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// cannot use SummaryOpts. Instead, a CounterOpts struct is created internally,
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// and all its fields are set to the equally named fields in the provided
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// SummaryOpts.
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func InstrumentHandlerWithOpts(opts SummaryOpts, handler http.Handler) http.HandlerFunc {
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return InstrumentHandlerFuncWithOpts(opts, handler.ServeHTTP)
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}
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// InstrumentHandlerFuncWithOpts works like InstrumentHandlerFunc (and shares
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// the same issues) but provides more flexibility (at the cost of a more complex
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// call syntax). See InstrumentHandlerWithOpts for details how the provided
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// SummaryOpts are used.
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func InstrumentHandlerFuncWithOpts(opts SummaryOpts, handlerFunc func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
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reqCnt := NewCounterVec(
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CounterOpts{
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Namespace: opts.Namespace,
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Subsystem: opts.Subsystem,
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Name: "requests_total",
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Help: "Total number of HTTP requests made.",
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ConstLabels: opts.ConstLabels,
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},
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instLabels,
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)
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opts.Name = "request_duration_microseconds"
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opts.Help = "The HTTP request latencies in microseconds."
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reqDur := NewSummary(opts)
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opts.Name = "request_size_bytes"
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opts.Help = "The HTTP request sizes in bytes."
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reqSz := NewSummary(opts)
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opts.Name = "response_size_bytes"
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opts.Help = "The HTTP response sizes in bytes."
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resSz := NewSummary(opts)
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regReqCnt := MustRegisterOrGet(reqCnt).(*CounterVec)
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regReqDur := MustRegisterOrGet(reqDur).(Summary)
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regReqSz := MustRegisterOrGet(reqSz).(Summary)
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regResSz := MustRegisterOrGet(resSz).(Summary)
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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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delegate := &responseWriterDelegator{ResponseWriter: w}
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out := make(chan int)
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urlLen := 0
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if r.URL != nil {
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urlLen = len(r.URL.String())
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}
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go computeApproximateRequestSize(r, out, urlLen)
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_, cn := w.(http.CloseNotifier)
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_, fl := w.(http.Flusher)
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_, hj := w.(http.Hijacker)
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_, rf := w.(io.ReaderFrom)
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var rw http.ResponseWriter
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if cn && fl && hj && rf {
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rw = &fancyResponseWriterDelegator{delegate}
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} else {
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rw = delegate
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}
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handlerFunc(rw, r)
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elapsed := float64(time.Since(now)) / float64(time.Microsecond)
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method := sanitizeMethod(r.Method)
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code := sanitizeCode(delegate.status)
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regReqCnt.WithLabelValues(method, code).Inc()
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regReqDur.Observe(elapsed)
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regResSz.Observe(float64(delegate.written))
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regReqSz.Observe(float64(<-out))
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})
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}
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func computeApproximateRequestSize(r *http.Request, out chan int, s int) {
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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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out <- s
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}
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type responseWriterDelegator struct {
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http.ResponseWriter
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handler, method string
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status int
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written int64
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wroteHeader bool
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}
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func (r *responseWriterDelegator) WriteHeader(code int) {
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r.status = code
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r.wroteHeader = true
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r.ResponseWriter.WriteHeader(code)
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}
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func (r *responseWriterDelegator) Write(b []byte) (int, error) {
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if !r.wroteHeader {
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r.WriteHeader(http.StatusOK)
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}
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n, err := r.ResponseWriter.Write(b)
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r.written += int64(n)
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return n, err
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}
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type fancyResponseWriterDelegator struct {
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*responseWriterDelegator
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}
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func (f *fancyResponseWriterDelegator) CloseNotify() <-chan bool {
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return f.ResponseWriter.(http.CloseNotifier).CloseNotify()
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}
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func (f *fancyResponseWriterDelegator) Flush() {
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f.ResponseWriter.(http.Flusher).Flush()
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}
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func (f *fancyResponseWriterDelegator) Hijack() (net.Conn, *bufio.ReadWriter, error) {
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return f.ResponseWriter.(http.Hijacker).Hijack()
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}
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func (f *fancyResponseWriterDelegator) ReadFrom(r io.Reader) (int64, error) {
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if !f.wroteHeader {
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f.WriteHeader(http.StatusOK)
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}
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n, err := f.ResponseWriter.(io.ReaderFrom).ReadFrom(r)
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f.written += n
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return n, err
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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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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:
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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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