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