fiber/middleware/expvar

Expvar Middleware

Expvar middleware for Fiber that serves via its HTTP server runtime exposed variants in the JSON format. The package is typically only imported for the side effect of registering its HTTP handlers. The handled path is /debug/vars.

• Expvar Middleware
  • Signatures
  • Example

Signatures

func New() fiber.Handler

Example

Import the expvar package that is part of the Fiber web framework

package main

import (
	"expvar"
	"fmt"

	"github.com/gofiber/fiber/v3"
	expvarmw "github.com/gofiber/fiber/v3/middleware/expvar"
)

var count = expvar.NewInt("count")

func main() {
	app := fiber.New()
	app.Use(expvarmw.New())
	app.Get("/", func(c fiber.Ctx) error {
		count.Add(1)

		return c.SendString(fmt.Sprintf("hello expvar count %d", count.Value()))
	})

	fmt.Println(app.Listen(":3000"))
}

Visit path /debug/vars to see all vars and use query r=key to filter exposed variables.

curl 127.0.0.1:3000
hello expvar count 1

curl 127.0.0.1:3000/debug/vars
{
	"cmdline": ["xxx"],
	"count": 1,
	"expvarHandlerCalls": 33,
	"expvarRegexpErrors": 0,
	"memstats": {...}
}

curl 127.0.0.1:3000/debug/vars?r=c
{
	"cmdline": ["xxx"],
	"count": 1
}

Config

// Config defines the config for middleware.
type Config struct {	
	// Next defines a function to skip this middleware when returned true.
	//
	// Optional. Default: nil
	Next func(c fiber.Ctx) bool
}

Default Config

var ConfigDefault = Config{
	Next: nil,
}