Logged request URLs contain duplicate host/port (e.g., "http://example.comhttp://example.com/api")

[seb-schulz]

Problem:
When using httplog with structured logging (e.g., SchemaGCP), the requestUrl field in logs incorrectly duplicates the host and port:

{
  "httpRequest": {
    "requestUrl": "http://localhost:8080http://localhost:8080/api/users",  // ❌ Duplicated
    "requestMethod": "GET",
    "requestPath": "/api/users"
  }
}

Expected:

{
  "httpRequest": {
    "requestUrl": "http://localhost:8080/api/users",  // ✅ Correct
    "requestMethod": "GET",
    "requestPath": "/api/users"
  }
}

How to Reproduce:

var requestLogger = httplog.RequestLogger(slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
	Level: slog.LevelInfo,
})), &httplog.Options{
	Level:         slog.LevelInfo,
	RecoverPanics: true,
	Schema:        httplog.SchemaGCP,
})

1. Use the logger middleware in your application.
2. Make a request to any endpoint.
3. Check the logs: The requestUrl field will show the host/port twice.

[sakchhu]

I could not reproduce it with the _example, modifying the Schema to SchemaGCP. Can you provide a minimal reproducible example? Maybe something's off with how you're configuring the logger?

[seb-schulz]

I noticed a difference when running behind a reverse proxy to a FCGI handler.

Run go run ./ with the following code:

package main

import (
	"fmt"
	"log"
	"log/slog"
	"net"
	"net/http"
	"net/http/fcgi"
	"os"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/httplog/v3"
)

var requestLogger = httplog.RequestLogger(slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
	Level: slog.LevelInfo,
})), &httplog.Options{
	Level:         slog.LevelInfo,
	RecoverPanics: true,
	Schema:        httplog.SchemaGCP,
})

func main() {
	r := chi.NewRouter()
	r.Use(requestLogger)

	r.Get("/*", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Request to URL: %s\n", r.URL)
	})

	ln, err := net.Listen("tcp", ":9010")
	if err != nil {
		log.Fatalf("failed to listen on 9010: %v", err)
	}
	if err := fcgi.Serve(ln, r); err != nil {
		log.Fatalf("failed to start fcgi instance: %v", err)
	}
	// if err := http.ListenAndServe(":9010", r); err != nil {
	// 	log.Fatalf("failed to start fcgi instance: %v", err)
	// }
}

Run caddy run in a second terminal with the following Caddyfile:

{
	auto_https off
	http_port 9011
	admin off
}

localhost:9011 {
	reverse_proxy :9010 {
		transport fastcgi
	}
}

Run in a third terminal curl 'http://localhost:9011/hello' which returns Request to URL: http://localhost:9011/hello.
When I do the same with http instead of fcgi, the responds is Request to URL: /hello without schema, host and port.

The entire example is also available under https://gist.github.com/seb-schulz/5f01652ad7eb77a70499c6ee092af72f