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Expose additional HTTP metrics #3698

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#3748
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Expose additional HTTP metrics#3698
#3748
@IvoGoman

Description

@IvoGoman
IvoGoman
opened on Aug 15, 2024

Preflight Checklist

  • I agree to follow the Code of Conduct that this project adheres to.
  • I have searched the issue tracker for an issue that matches the one I want to file, without success.

Problem Description

Currently dex exposes only http_requests_total{handler="", code="",method=""} as a metric. The method used to calculate these metrics also collect the Duration and Response size written. https://github.com/felixge/httpsnoop/blob/master/capture_metrics.go#L46-L82
These metrics are not exposed.

Proposed Solution

Additional histogram metrics:

  • http_request_duration_seconds{handler="", code="", method=""}
  • http_response_size_bytes{handler="", code="", method=""}.

Which can be added to the handler instrumentalization here:

dex/server/server.go

Lines 335 to 356 in 5c66c71

instrumentHandlerCounter := func(_ string, handler http.Handler) http.HandlerFunc {
return handler.ServeHTTP
}
if c.PrometheusRegistry != nil {
requestCounter := prometheus.NewCounterVec(prometheus.CounterOpts{
Name: "http_requests_total",
Help: "Count of all HTTP requests.",
}, []string{"handler", "code", "method"})
err = c.PrometheusRegistry.Register(requestCounter)
if err != nil {
return nil, fmt.Errorf("server: Failed to register Prometheus HTTP metrics: %v", err)
}
instrumentHandlerCounter = func(handlerName string, handler http.Handler) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
m := httpsnoop.CaptureMetrics(handler, w, r)
requestCounter.With(prometheus.Labels{"handler": handlerName, "code": strconv.Itoa(m.Code), "method": r.Method}).Inc()
}
}
}

Since native histograms are not yet GA, there is the open question of which Buckets make sense for these metrics.

Alternatives Considered

No response

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