Serve large files
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Jeffrey Smith
Feb 28, 2017, 6:13:20 AM2/28/17
to golang-nuts
I'm trying to server up a file that can be very large so would like to try and stream the content back.
I tried using this but I believe ioutil.readFile actually calls ioutil.readAll so sticks the whole content of the file into a byte array. What am i doing wrong?
package main
import ( "bytes" "fmt" //"io" "io/ioutil" "log" "net/http")
func main() {
http.HandleFunc("/", serverFile) if err := http.ListenAndServe(":8085", nil); err != nil { log.Fatal(err) }
}
func serverFile(w http.ResponseWriter, r *http.Request) {
streamPDFbytes, err := ioutil.ReadFile("./large.txt") if err != nil { fmt.Println(err) return }
b := bytes.NewBuffer(streamPDFbytes)
w.Header().Set("Content-Disposition", "attachment;filename=large.txt") //io.Copy(w, b) if _, err := b.WriteTo(w); err != nil { fmt.Fprintf(w, "%s", err) }}I tried using this but I believe ioutil.readFile actually calls ioutil.readAll so sticks the whole content of the file into a byte array. What am i doing wrong?
Jordan Krage
Feb 28, 2017, 6:34:04 AM2/28/17
to golang-nuts
Try using os.Open to get a *File (which implements io.Reader), and then io.Copy to the response from the file.
Jeffrey Smith
Feb 28, 2017, 7:05:19 AM2/28/17
to golang-nuts
Works perfectly. cheers
package main
import ( "fmt" "io" "log" "net/http" "os")
func main() {
http.HandleFunc("/", serverFile) if err := http.ListenAndServe(":8085", nil); err != nil { log.Fatal(err) }
}
func serverFile(w http.ResponseWriter, r *http.Request) {
streamPDFbytes, err := os.Open("./large.txt") if err != nil { fmt.Println(err) return }
w.Header().Set("Content-Disposition", "attachment;filename=large.txt") io.Copy(w, streamPDFbytes)}
Christian Joergensen
Feb 28, 2017, 7:19:10 AM2/28/17
to golang-nuts
Hello,
I'd recommend you take a look at:
This also gives you support for range requests and other goodies.
Cheers,
Christian
Jesse McNelis
Feb 28, 2017, 7:19:13 AM2/28/17
to golang-nuts
Try using os.Open to get a *File (which implements io.Reader), and then io.Copy to the response from the file.
You should use https://golang.org/pkg/net/http/#ServeFile that's what it does. It will also handle requests with range headers for allowing the client to fetch just a part of the file.
Tamás Gulácsi
Feb 28, 2017, 8:12:52 AM2/28/17
to golang-nuts
A "defer streamPDFbytes.Close()" is missing - you'll run out of file descriptors...
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