Disable certain prometheus metrics #109

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1. aldas commented on Feb 1, 2024

   

   aldas

   on Feb 1, 2024

   Contributor

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   Nope, requests_total, request_duration_seconds, response_size_bytes, request_size_bytes are built in.

   but if you are OK not having histograms then it leaves you only with requests_total as this is counter. You could strip down the middleware to something like that and add your custom metrics if needed.

   func myPrometheusRoute() echo.HandlerFunc {
   	gatherer := prometheus.DefaultGatherer
   	h := promhttp.HandlerFor(gatherer, promhttp.HandlerOpts{DisableCompression: true})
   
   	if r, ok := gatherer.(prometheus.Registerer); ok {
   		h = promhttp.InstrumentMetricHandler(r, h)
   	}
   
   	return func(c echo.Context) error {
   		h.ServeHTTP(c.Response(), c.Request())
   		return nil
   	}
   }
   
   func myPrometheusMW() (echo.MiddlewareFunc, error) {
   	requestCount := prometheus.NewCounterVec(
   		prometheus.CounterOpts{
   			Namespace: "",
   			Subsystem: "MY_APP",
   			Name:      "requests_total",
   			Help:      "How many HTTP requests processed, partitioned by status code and HTTP method.",
   		},
   		[]string{"code", "method", "host", "url"},
   	)
   	if err := prometheus.DefaultRegisterer.Register(requestCount); err != nil {
   		return nil, err
   	}
   
   	return func(next echo.HandlerFunc) echo.HandlerFunc {
   		return func(c echo.Context) error {
   			err := next(c)
   			status := c.Response().Status
   			if err != nil {
   				var httpError *echo.HTTPError
   				if errors.As(err, &httpError) {
   					status = httpError.Code
   				}
   				if status == 0 || status == http.StatusOK {
   					status = http.StatusInternalServerError
   				}
   			}
   
   			url := c.Path() // contains route path ala `/users/:id`
   			if url == "" {
   				// as of Echo v4.10.1 path is empty for 404 cases (when router did not find any matching routes)
   				// in this case we use actual path from request to have some distinction in Prometheus
   				url = c.Request().URL.Path
   			}
   
   			requestCount.WithLabelValues(
   				strconv.Itoa(status),
   				c.Request().Method,
   				c.Request().Host,
   				url,
   			).Inc()
   			return err
   		}
   	}, nil
   }

   This is https://github.com/labstack/echo-contrib/tree/master/echoprometheus stripped down
2. aldas commented on Feb 1, 2024

   

   aldas

   on Feb 1, 2024

   Last edited by aldas

   Contributor

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   NB: you might need custom registry. This does not contain prometheus own default metrics

   customRegistry := prometheus.NewRegistry() // create custom registry for your custom metrics

   and make sure that you Route takes that registry in as gatherer

   e.GET("/metrics", myPrometheusRoute(customRegistry))

   and myPrometheusMW needs to use that same customRegistry to register metrics
3. ivanovaleksandar commented on Feb 1, 2024

   

   ivanovaleksandar

   on Feb 1, 2024

   Author

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   @aldas thank you for providing a workaround. I replicated almost the same locally, but was wondering if there is something that I am missing here.

   Anyways, is it something that you want implemented? I mean, the optional disabling of these types of metrics.