otelmetricsecho

otelmetricsecho is a middleware for the Echo web framework that integrates OpenTelemetry metrics for monitoring HTTP requests. It provides various metrics, including request count, duration, response size, and request size, helping with observability and performance tracking.

Features

Tracks HTTP request count, duration, request size, and response size.
Supports configurable label functions for custom metric attributes.
Uses OpenTelemetry for metric instrumentation.
Handles 404 and other error responses gracefully.

Installation

go get github.com/overtonx/otelmetricsecho

Usage

Basic Middleware Setup

package main

import (
    "github.com/labstack/echo/v4"
    "github.com/overtonx/otel-metrics-echo"
)

func main() {
	e := echo.New()
	e.Use(otelmetricsecho.NewMiddleware("myapp"))

	e.GET("/hello", func(c echo.Context) error {
		return c.String(200, "Hello, World!")
	})

	e.Start(":8080")
}

Custom Middleware Configuration

	config := otelmetricsecho.MiddlewareConfig{
		DoNotUseRequestPathFor404: true,
	}

	e.Use(otelmetricsecho.NewMiddlewareWithConfig(config))

LabelFuncs

The LabelFuncs map allows you to append custom labels to the generated metrics by defining functions that extract values from the request context. This can be useful for adding custom metadata to your metrics, such as tenant IDs, user roles, or feature flags.

Example: Adding Custom Metrics Labels

config := otelmetricsecho.MiddlewareConfig{
	LabelFuncs: map[string]otelmetricsecho.LabelValueFunc{
		"tenant_id": func(c echo.Context, err error) string {
			return c.Request().Header.Get("X-Tenant-ID")
		},
		"user_role": func(c echo.Context, err error) string {
			return c.Request().Header.Get("X-User-Role")
		},
	},
}

e.Use(otelmetricsecho.NewMiddlewareWithConfig(config))

This configuration ensures that every metric emitted by the middleware contains additional labels tenant_id and user_role extracted from the request headers.

Metrics Provided

Request Count

Metric Name: requests_total
Description: Number of HTTP requests processed, partitioned by status code and method.

Request Duration

Metric Name: request_duration_seconds
Description: The HTTP request latencies in seconds.

Request Size

Metric Name: request_size_bytes
Description: The HTTP request sizes in bytes.

Response Size

Metric Name: response_size_bytes
Description: The HTTP response sizes in bytes.

# README