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// __ _____ __ ___ ___ __ _| |_ ___
// \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
// \ V V / __/ (_| |\ V /| | (_| | || __/
// \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
//
// Copyright © 2016 - 2025 Weaviate B.V. All rights reserved.
//
// CONTACT: hello@weaviate.io
//
package monitoring
import (
"io"
"net/http"
"strconv"
"github.com/felixge/httpsnoop"
"github.com/prometheus/client_golang/prometheus"
)
// StaticRouteLabel takes any http request and return canonical and static route label
// that can used in metrics without worrying about unbounded cardinality.
// Examples:
// `/schema/Movies/properties` -> `/schema/{className}`
// `/replicas/indices/Movies/shards/hello0/objects` -> `/replicas/indices`
type StaticRouteLabel func(r *http.Request) (*http.Request, string)
type InstrumentHandler struct {
inflightRequests *prometheus.GaugeVec
duration *prometheus.HistogramVec
// in bytes
requestSize *prometheus.HistogramVec
responseSize *prometheus.HistogramVec
// next is original http handler we instrument
next http.Handler
routeLabel StaticRouteLabel
}
func InstrumentHTTP(
next http.Handler,
routeLabel StaticRouteLabel,
inflight *prometheus.GaugeVec,
duration *prometheus.HistogramVec,
requestSize *prometheus.HistogramVec,
responseSize *prometheus.HistogramVec,
) *InstrumentHandler {
return &InstrumentHandler{
next: next,
routeLabel: routeLabel,
inflightRequests: inflight,
duration: duration,
requestSize: requestSize,
responseSize: responseSize,
}
}
func (i *InstrumentHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
r, route := i.routeLabel(r)
method := r.Method
inflight := i.inflightRequests.WithLabelValues(method, route)
inflight.Inc()
defer inflight.Dec()
origBody := r.Body
defer func() {
// We don't need `countingReadCloser` before this instrument handler
r.Body = origBody
}()
cr := &countingReadCloser{
r: r.Body,
}
r.Body = cr
// This is where we run actual upstream http.Handler
respWithMetrics := httpsnoop.CaptureMetricsFn(w, func(rw http.ResponseWriter) {
i.next.ServeHTTP(rw, r)
})
i.requestSize.WithLabelValues(method, route).Observe(float64(cr.read))
i.responseSize.WithLabelValues(method, route).Observe(float64(respWithMetrics.Written))
labelValues := []string{
method,
route,
strconv.Itoa(respWithMetrics.Code),
}
i.duration.WithLabelValues(labelValues...).Observe(respWithMetrics.Duration.Seconds())
}
type countingReadCloser struct {
r io.ReadCloser
read int64
}
func (c *countingReadCloser) Read(p []byte) (int, error) {
n, err := c.r.Read(p)
if n > 0 {
c.read += int64(n)
}
return n, err
}
func (c *countingReadCloser) Close() error {
return c.r.Close()
}
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