README.md

Prometheus

Prometheus middleware for Fiber v3 based on ansrivas/fiberprometheus.

Following metrics are available by default:

http_requests_total
http_requests_status_class_total
http_request_duration_seconds
http_requests_in_progress
http_request_size_bytes
http_response_size_bytes

http_requests_in_progress exposes both the HTTP method and normalized route path so you can pinpoint which handlers are currently running.

Note

The middleware requires Go 1.25 or newer and Fiber v3 (currently RC).

🚀 Installation

go get github.com/gofiber/contrib/v3/prometheus

📄 Example

package main

import (
	fiberprometheus "github.com/gofiber/contrib/v3/prometheus"
	"github.com/gofiber/fiber/v3"
)

func main() {
        app := fiber.New()

	app.Use("/metrics", fiberprometheus.New(fiberprometheus.Config{
		Service:           "my-service-name",
		SkipURIs:          []string{"/ping"},
		IgnoreStatusCodes: []int{401, 403, 404},
	}))

        app.Get("/", func(c fiber.Ctx) error {
                return c.SendString("Hello World")
        })

        app.Get("/ping", func(c fiber.Ctx) error {
                return c.SendString("pong")
        })

        app.Post("/some", func(c fiber.Ctx) error {
                return c.SendString("Welcome!")
        })

        app.Listen(":3000")
}

Collector, OpenMetrics, and response options

The middleware exposes Prometheus collector toggles and HandlerOpts via Config. By default it creates a private Registerer/Gatherer pair and uses that for both registration and scraping. When customizing the registry, ensure that the Registerer and Gatherer refer to the same metrics source (for example, a *prometheus.Registry). Supplying only one that does not implement the other interface or providing a mismatched pair will cause initialization to panic so metrics are not silently dropped.

• DisableGoCollector disables the default Go runtime metrics collector when set to true.

• DisableProcessCollector disables the default process metrics collector when set to true.

• EnableOpenMetrics negotiates the experimental OpenMetrics encoding so exemplars are exported.

• EnableOpenMetricsTextCreatedSamples adds synthetic _created samples when OpenMetrics is enabled.

• DisableCompression disables gzip/zstd compression even when clients request it.

• TrackUnmatchedRequests records metrics for requests that miss all registered routes using UnmatchedRouteLabel as the path label. Defaults to false.

• UnmatchedRouteLabel customizes the path label applied to unmatched requests when tracking is enabled. Defaults to /__unmatched__.

• RequestDurationBuckets, RequestSizeBuckets, and ResponseSizeBuckets customize the histogram buckets used for latency and payload metrics. They default to:

  • Duration: [0.005 0.01 0.025 0.05 0.075 0.1 0.25 0.5 0.75 1 2.5 5 10 15 30 60]
  • Request size: [256 512 1024 2048 4096 8192 16384 32768 65536 131072 262144 524288 1048576 2097152 5242880]
  • Response size: [256 512 1024 2048 4096 8192 16384 32768 65536 131072 262144 524288 1048576 2097152 5242880]

All of the options default to false and can be enabled or disabled individually as needed.

The metrics endpoint path is derived from how the middleware is mounted. In the example above, calling app.Use("/metrics", fiberprometheus.New(...)) exposes the handler at /metrics while the middleware continues to instrument all routed traffic.

📊 Result

• Hit the default url at http://localhost:3000
• Navigate to http://localhost:3000/metrics
• Metrics are recorded only for routes registered with Fiber unless TrackUnmatchedRequests is enabled, in which case unmatched requests are labeled with UnmatchedRouteLabel.

📈 Grafana Dashboard

• https://grafana.com/grafana/dashboards/14331