Adds middleware to insert X-Request-Start unix millis timestamp

[AxelTheGerman]

Implements #69

Note: I never wrote a line of Go before. I based everything on the X-Request-ID middleware implementation.

PS: make test passes for me locally

[AxelTheGerman]

@kevinmcconnell if you have a moment, I would appreciate your take on this feature/PR. Thank you so much for bringing all this to life, I was looking for something like Kamal for years 🚀

[kwilczynski]

Either:

Suggested change

	var now = time.Now().UnixMilli()
	return strconv.FormatInt(now, 10)
	now := time.Now().UnixMilli()
	return strconv.FormatInt(now, 10)

Or:

Suggested change

	var now = time.Now().UnixMilli()
	return strconv.FormatInt(now, 10)
	return strconv.FormatInt(time.Now().UnixMilli(), 10)

[kwilczynski]

Suggested change

	id := r.Header.Get("X-Request-Start")
	assert.NotEmpty(t, id)
	timestamp := r.Header.Get("X-Request-Start")
	assert.NotEmpty(t, timestamp)

[kwilczynski]

Suggested change

	id := r.Header.Get("X-Request-Start")
	assert.Equal(t, "1234", id)
	timestamp := r.Header.Get("X-Request-Start")
	assert.Equal(t, "1234", timestamp)

[kwilczynski]

Add this at the top:

const (
	requestStartHeader = "X-Request-Start"
)

Suggested change

	if r.Header.Get("X-Request-Start") == "" {
	r.Header.Set("X-Request-Start", h.nowStr())
	}
	if r.Header.Get(requestStartHeader) == "" {
	r.Header.Set(requestStartHeader, h.nowStr())
	}

You can then also reuse this in tests.

[kwilczynski]

Either:

Suggested change

	func (h *RequestStartMiddleware) nowStr() string {
	func (h *RequestStartMiddleware) nowString() string {

Or:

Suggested change

	func (h *RequestStartMiddleware) nowStr() string {
	func (h *RequestStartMiddleware) timestamp() string {

[kwilczynski]

You could also ditch this helper completely and use the following directly:

strconv.FormatInt(time.Now().UnixMilli(), 10)

[kwilczynski]

You probably should add this before or after the WithRequestIDMiddleware() handler so that this is injected as early as possible, given that handlers are executed in the inverse order.

An option would be to augment the WithRequestIDMiddleware() handler with the new header it would inject.

[AxelTheGerman]

Awesome, didn't realize they get executed in reverse. Wanted to add this one first. Thank you.

[kwilczynski]

No worries. @AxelTheGerman, you can see this with a simpler example:

  package main

  import (
          "fmt"
          "net/http"
  )

  func One(h http.Handler) http.Handler {
          return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
                  fmt.Println("One")
                  h.ServeHTTP(w, r)
                  fmt.Println("One")
          })
  }

  func Two(h http.Handler) http.Handler {
          return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
                  fmt.Println("Two")
                  h.ServeHTTP(w, r)
                  fmt.Println("Two")
          })
  }

  func Main(h http.Handler) http.Handler {
          return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
                  fmt.Println("Main")
          })
  }

  func main() {
          mux := http.NewServeMux()

          handler := Main(mux)
          handler = Two(handler)
          handler = One(handler)

          mux.Handle("/", handler)
          panic(http.ListenAndServe(":3000", mux))
  }

Then, sending a single request against TCP/3000, per:

$ go run main.go
^Z
[1]+  Stopped                 go run main.go
$ bg
[1]+ go run main.go &
$ curl -v 0:3000
*   Trying 0.0.0.0:3000...
* Connected to 0.0.0.0 (0.0.0.0) port 3000
* using HTTP/1.x
> GET / HTTP/1.1
> Host: 0.0.0.0:3000
> User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
> Accept: */*
>
* Request completely sent off
One
Two
Main
Two
One
< HTTP/1.1 200 OK
< Date: Sun, 24 Nov 2024 15:40:48 GMT
< Content-Length: 0
<
* Connection #0 to host 0.0.0.0 left intact
$ fg
go run main.go
^Csignal: interrupt

You chain the execution of each handler, which becomes a callback, so to speak, which runs the handler you passed into it, hence the inverse order in which these run. I hope this makes sense.

There are some nice packages such as the justinas/alice that aim to make this pattern a little bit more grounded.

[kwilczynski]

@AxelTheGerman, feel free to squash the commits into one.

[AxelTheGerman]

@AxelTheGerman, feel free to squash the commits into one.

Done!

Thanks again for the review and additional information on how everything works.

[kwilczynski]

@AxelTheGerman, feel free to squash the commits into one.

Done!

Thanks again for the review and additional information on how everything works.

@AxelTheGerman, my pleasure. Thank you for your contribution! Much appreciated. 🎉

We now need to wait for one of the maintainers to do a final round of reviews, etc.

[kevinmcconnell]

This is great, thanks @AxelTheGerman for the contribution, and @kwilczynski for the review. 🙏

Nice work! 👏