chromedp/examples/pool/main.go

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2017-04-05 03:00:51 +00:00
package main
import (
"context"
"fmt"
"io/ioutil"
"log"
"sync"
"time"
cdp "github.com/knq/chromedp"
cdptypes "github.com/knq/chromedp/cdp"
"github.com/knq/chromedp/cdp/page"
)
func main() {
var err error
// create context
ctxt, cancel := context.WithCancel(context.Background())
defer cancel()
// create pool
pool, err := cdp.NewPool( /*cdp.PoolLog(log.Printf, log.Printf, log.Printf)*/ )
if err != nil {
log.Fatal(err)
}
// loop over the URLs
var wg sync.WaitGroup
for i, urlstr := range []string{
"https://brank.as/",
"https://brank.as/careers",
"https://brank.as/about",
} {
wg.Add(1)
go takeScreenshot(ctxt, &wg, pool, i, urlstr)
}
// wait for to finish
wg.Wait()
// shutdown pool
err = pool.Shutdown()
if err != nil {
log.Fatal(err)
}
}
func takeScreenshot(ctxt context.Context, wg *sync.WaitGroup, pool *cdp.Pool, id int, urlstr string) {
defer wg.Done()
// allocate
c, err := pool.Allocate(ctxt)
if err != nil {
log.Printf("url (%d) `%s` error: %v", id, urlstr, err)
return
}
defer c.Release()
// run tasks
var buf []byte
err = c.Run(ctxt, screenshot(urlstr, &buf))
if err != nil {
log.Printf("url (%d) `%s` error: %v", id, urlstr, err)
return
}
// write to disk
err = ioutil.WriteFile(fmt.Sprintf("%d.png", id), buf, 0644)
if err != nil {
log.Printf("url (%d) `%s` error: %v", id, urlstr, err)
return
}
}
func screenshot(urlstr string, picbuf *[]byte) cdp.Action {
return cdp.Tasks{
cdp.Navigate(urlstr),
cdp.Sleep(2 * time.Second),
cdp.WaitVisible(`#navbar-nav-main`),
cdp.ActionFunc(func(ctxt context.Context, h cdptypes.Handler) error {
buf, err := page.CaptureScreenshot().Do(ctxt, h)
if err != nil {
return err
}
*picbuf = buf
return nil
}),
}
}