I'm trying to use ServeContent to serve files (which may be large movie files, so it will use byte ranges), but I'm not sure how to handle the modified time. If I use the following program to serve a movie, it fails if I give the actual modified time of the file as shown. I think what happens is that the first request works, but subsequent ones (of different byte ranges of the file) think it already has the file and therefore they fail and the movie doesn't play. Is there something I am doing wrong?
Note that the code works (and the movie plays properly) if I use time.Now() instead of the actual modified time of the file, but that isn't correct of course.
package main
import (
"fmt"
"net/http"
"os"
"path"
"time"
)
func main() {
http.HandleFunc("/", handler)
http.ListenAndServe(":3000", nil)
}
func handler(w http.ResponseWriter, r *http.Request) {
filePath := "." + r.URL.Path
file, err := os.Open(filePath)
if err != nil {
fmt.Printf("%s not found
", filePath)
w.WriteHeader(http.StatusNotFound)
fmt.Fprint(w, "<html><body style='font-size:100px'>four-oh-four</body></html>")
return
}
defer file.Close()
fileStat, err := os.Stat(filePath)
if err != nil {
fmt.Println(err)
}
fmt.Printf("serve %s
", filePath)
_, filename := path.Split(filePath)
t := fileStat.ModTime()
fmt.Printf("time %+v
", t)
http.ServeContent(w, r, filename, t, file)
}
According to the documentation,
If modtime is not the zero time, ServeContent includes it in a Last-Modified header in the response. If the request includes an If-Modified-Since header, ServeContent uses modtime to decide whether the content needs to be sent at all.
So, depending on whether the client sends the If-Modified-Since header, this function will behave correctly or not. This seems to be the intended behaviour, and is indeed useful in normal situations to optimize the server's bandwidth.
In your case, however, as you have to handle partial-content requests, unless the first request returns a 30X HTTP code, you have no reason to handle this mechanism for subsequent requests.
The correct way to disable this behaviour is to pass a "zero" date to ServeContent:
http.ServeContent(w, r, filename, time.Time{}, file)
You could try to parse the request range header in order to only pass a zero date if necessary.