-
Notifications
You must be signed in to change notification settings - Fork 0
/
fetchall.go
57 lines (47 loc) · 1.37 KB
/
fetchall.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
// Fetch URLs in parallel and report their times and sizes.
//
// The Go Programming Language, 1.6: https://github.com/adonovan/gopl.io/tree/master/ch1/fetchall
//
// $ go build fetchall.go
// $ ./fetchall https://golang.org http://perl.org http://reisinge.net
package main
import (
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"time"
)
func main() { // main runs in a goroutine
start := time.Now()
ch := make(chan string) // channel -- a communication mechanism that
// allows one goroutine to pass values of a
// specified type to another goroutine
for _, url := range os.Args[1:] {
go fetch(url, ch) // create additional goroutine
// goroutine -- a concurrent function execution
}
for range os.Args[1:] {
fmt.Println(<-ch) // receive from channel ch
}
fmt.Printf("%.2fs elapsed\n", time.Since(start).Seconds())
}
func fetch(url string, ch chan<- string) {
start := time.Now()
resp, err := http.Get(url)
if err != nil {
ch <- fmt.Sprint(err) // send to channel ch
return
}
// io.Copy function reads the body of the response and discards it by
// writing to the ioutil.Discard output stream.
nbytes, err := io.Copy(ioutil.Discard, resp.Body)
resp.Body.Close() // don't leak resources
if err != nil {
ch <- fmt.Sprintf("while reading %s: %v", url, err)
return
}
secs := time.Since(start).Seconds()
ch <- fmt.Sprintf("%.2fs %7d %s", secs, nbytes, url)
}