85 lines
2.3 KiB
Go
85 lines
2.3 KiB
Go
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package httpsnoop
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import (
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"io"
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"net/http"
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"sync"
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"time"
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)
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// Metrics holds metrics captured from CaptureMetrics.
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type Metrics struct {
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// Code is the first http response code passed to the WriteHeader func of
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// the ResponseWriter. If no such call is made, a default code of 200 is
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// assumed instead.
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Code int
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// Duration is the time it took to execute the handler.
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Duration time.Duration
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// Written is the number of bytes successfully written by the Write or
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// ReadFrom function of the ResponseWriter. ResponseWriters may also write
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// data to their underlaying connection directly (e.g. headers), but those
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// are not tracked. Therefor the number of Written bytes will usually match
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// the size of the response body.
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Written int64
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}
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// CaptureMetrics wraps the given hnd, executes it with the given w and r, and
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// returns the metrics it captured from it.
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func CaptureMetrics(hnd http.Handler, w http.ResponseWriter, r *http.Request) Metrics {
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return CaptureMetricsFn(w, func(ww http.ResponseWriter) {
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hnd.ServeHTTP(ww, r)
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})
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}
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// CaptureMetricsFn wraps w and calls fn with the wrapped w and returns the
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// resulting metrics. This is very similar to CaptureMetrics (which is just
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// sugar on top of this func), but is a more usable interface if your
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// application doesn't use the Go http.Handler interface.
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func CaptureMetricsFn(w http.ResponseWriter, fn func(http.ResponseWriter)) Metrics {
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var (
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start = time.Now()
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m = Metrics{Code: http.StatusOK}
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headerWritten bool
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lock sync.Mutex
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hooks = Hooks{
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WriteHeader: func(next WriteHeaderFunc) WriteHeaderFunc {
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return func(code int) {
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next(code)
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lock.Lock()
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defer lock.Unlock()
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if !headerWritten {
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m.Code = code
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headerWritten = true
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}
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}
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},
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Write: func(next WriteFunc) WriteFunc {
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return func(p []byte) (int, error) {
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n, err := next(p)
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lock.Lock()
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defer lock.Unlock()
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m.Written += int64(n)
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headerWritten = true
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return n, err
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}
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},
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ReadFrom: func(next ReadFromFunc) ReadFromFunc {
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return func(src io.Reader) (int64, error) {
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n, err := next(src)
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lock.Lock()
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defer lock.Unlock()
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headerWritten = true
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m.Written += n
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return n, err
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}
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},
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}
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)
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fn(Wrap(w, hooks))
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m.Duration = time.Since(start)
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return m
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}
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