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package caddyhttp
import (
"context"
"net/http"
"strconv"
"sync"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
)
var httpMetrics = struct {
init sync.Once
requestInFlight *prometheus.GaugeVec
requestCount *prometheus.CounterVec
requestErrors *prometheus.CounterVec
requestDuration *prometheus.HistogramVec
requestSize *prometheus.HistogramVec
responseSize *prometheus.HistogramVec
responseDuration *prometheus.HistogramVec
}{
init: sync.Once{},
}
func initHTTPMetrics() {
const ns, sub = "caddy", "http"
basicLabels := []string{"server", "handler"}
httpMetrics.requestInFlight = promauto.NewGaugeVec(prometheus.GaugeOpts{
Namespace: ns,
Subsystem: sub,
Name: "requests_in_flight",
Help: "Number of requests currently handled by this server.",
}, basicLabels)
httpMetrics.requestErrors = promauto.NewCounterVec(prometheus.CounterOpts{
Namespace: ns,
Subsystem: sub,
Name: "request_errors_total",
Help: "Number of requests resulting in middleware errors.",
}, basicLabels)
httpMetrics.requestCount = promauto.NewCounterVec(prometheus.CounterOpts{
Namespace: ns,
Subsystem: sub,
Name: "requests_total",
Help: "Counter of HTTP(S) requests made.",
}, basicLabels)
// TODO: allow these to be customized in the config
durationBuckets := prometheus.DefBuckets
sizeBuckets := prometheus.ExponentialBuckets(256, 4, 8)
httpLabels := []string{"server", "handler", "code", "method"}
httpMetrics.requestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
Namespace: ns,
Subsystem: sub,
Name: "request_duration_seconds",
Help: "Histogram of round-trip request durations.",
Buckets: durationBuckets,
}, httpLabels)
httpMetrics.requestSize = promauto.NewHistogramVec(prometheus.HistogramOpts{
Namespace: ns,
Subsystem: sub,
Name: "request_size_bytes",
Help: "Total size of the request. Includes body",
Buckets: sizeBuckets,
}, httpLabels)
httpMetrics.responseSize = promauto.NewHistogramVec(prometheus.HistogramOpts{
Namespace: ns,
Subsystem: sub,
Name: "response_size_bytes",
Help: "Size of the returned response.",
Buckets: sizeBuckets,
}, httpLabels)
httpMetrics.responseDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
Namespace: ns,
Subsystem: sub,
Name: "response_duration_seconds",
Help: "Histogram of times to first byte in response bodies.",
Buckets: durationBuckets,
}, httpLabels)
}
type ctxKeyServerName struct{}
// serverNameFromContext extracts the current server name from the context.
// Returns "UNKNOWN" if none is available (should probably never happen?)
func serverNameFromContext(ctx context.Context) string {
srvName, ok := ctx.Value(ctxKeyServerName{}).(string)
if !ok {
return "UNKNOWN"
}
return srvName
}
type metricsInstrumentedHandler struct {
labels prometheus.Labels
statusLabels prometheus.Labels
mh MiddlewareHandler
}
func newMetricsInstrumentedHandler(server, handler string, mh MiddlewareHandler) *metricsInstrumentedHandler {
httpMetrics.init.Do(func() {
initHTTPMetrics()
})
labels := prometheus.Labels{"server": server, "handler": handler}
statusLabels := prometheus.Labels{"server": server, "handler": handler, "code": "", "method": ""}
return &metricsInstrumentedHandler{labels, statusLabels, mh}
}
func (h *metricsInstrumentedHandler) ServeHTTP(w http.ResponseWriter, r *http.Request, next Handler) error {
inFlight := httpMetrics.requestInFlight.With(h.labels)
inFlight.Inc()
defer inFlight.Dec()
statusLabels := prometheus.Labels{"method": r.Method}
for k, v := range h.labels {
statusLabels[k] = v
}
start := time.Now()
// This is a _bit_ of a hack - it depends on the ShouldBufferFunc always
// being called when the headers are written.
// Effectively the same behaviour as promhttp.InstrumentHandlerTimeToWriteHeader.
writeHeaderRecorder := ShouldBufferFunc(func(status int, header http.Header) bool {
statusLabels["code"] = sanitizeCode(status)
ttfb := time.Since(start).Seconds()
observeWithExemplar(statusLabels, httpMetrics.responseDuration, ttfb)
return false
})
wrec := NewResponseRecorder(w, nil, writeHeaderRecorder)
err := h.mh.ServeHTTP(wrec, r, next)
dur := time.Since(start).Seconds()
httpMetrics.requestCount.With(h.labels).Inc()
if err != nil {
httpMetrics.requestErrors.With(h.labels).Inc()
return err
}
observeWithExemplar(statusLabels, httpMetrics.requestDuration, dur)
observeWithExemplar(statusLabels, httpMetrics.requestSize, float64(computeApproximateRequestSize(r)))
httpMetrics.responseSize.With(statusLabels).Observe(float64(wrec.Size()))
return nil
}
func observeWithExemplar(l prometheus.Labels, o *prometheus.HistogramVec, value float64) {
obs := o.With(l)
if oe, ok := obs.(prometheus.ExemplarObserver); ok {
oe.ObserveWithExemplar(value, l)
return
}
// _should_ be a noop, but here just in case...
obs.Observe(value)
}
func sanitizeCode(code int) string {
if code == 0 {
return "200"
}
return strconv.Itoa(code)
}
// taken from https://github.com/prometheus/client_golang/blob/6007b2b5cae01203111de55f753e76d8dac1f529/prometheus/promhttp/instrument_server.go#L298
func computeApproximateRequestSize(r *http.Request) int {
s := 0
if r.URL != nil {
s += len(r.URL.String())
}
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)
}
return s
}
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