[日常] Go语言圣经--并发的web爬虫

func main() {
worklist := make(chan []string)

    // Start with the command-line arguments.
    go func() { worklist <- os.Args[1:] }() 
    // Crawl the web concurrently.
    seen := make(map[string]bool)
    for list := range worklist {
            for _,link := range list {
                    if !seen[link] {
                            seen[link] = true
                            go func(link string) {
                                    worklist <- crawl(link)
                            }(link)
                    }   
            }   
    }   

}

var tokens = make(chan struct{},20)

//从一个url页面中提取出所有的url
func crawl(url string) []string {
fmt.Println(url)
tokens <- struct{}{}
list,err := links.Extract(url)
<-tokens
if err != nil {
//log.Print(err)
}
return list
}

func main() {
worklist := make(chan []string)
unseenLinks := make(chan string)

    // Start with the command-line arguments.
    go func() { worklist <- os.Args[1:] }() 
    // Create 20 crawler goroutines to fetch each unseen link.
    for i := 0; i < 20; i++ {
            go func() {
                    for link := range unseenLinks {
                            //if strings.HasPrefix(link,"http://www.lypeng.com") {
                            foundLinks := crawl(link)
                            go func() { worklist <- foundLinks }() 

                            //} 
                    }   
            }() 
    }   

    // The main goroutine de-duplicates worklist items
    // and sends the unseen ones to the crawlers.
    seen := make(map[string]bool)
    for list := range worklist {
            for _,link := range list {
                    if !seen[link] {
                            seen[link] = true
                            unseenLinks <- link
                    }   
            }   
    }   

}

//从一个url页面中提取出所有的url
func crawl(url string) []string {
fmt.Println(url)
list,err := links.Extract(url)
if err != nil {
//log.Print(err)
}
return list
}