我有一个golang应用程序,它在数据库中存储url(作为查询参数提供)。使用以下方法存储URL:
func AddArticle(db *sql.DB) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
queryParam := r.FormValue("url")
insertedId := dao.SaveArticle(db, queryParam)
glog.Infof("add hostname %s, id: %d", getHostnameFromUrl(queryParam), insertedId)
// start routine which scrapes url
go dao.ScrapeArticle(db, insertedId)
// finally output confirmation page
renderObject := map[string]string{"hostname": getHostnameFromUrl(queryParam)}
render.DisplayPage(w, r, renderObject, "confirmation.html")
}
}
现在这工作正常了,但是由于某些原因,当保存了很多新的url时,sqlite数据库告诉我发生了死锁。所以我想我想利用频道,只是为了防止那些死锁。但不幸的是,我不知道如何开始。
基本上,我想要的是:
对于每个添加的url,启动dao.scrapeArticle函数(将insertedID作为项目引用传递)。立即显示确认页(即
url added
)当完成对artcle的抓取时,函数会将抓取的信息添加到sqlite数据库(通过更新id)
我不知道怎么开始,需要帮助。我在哪里定义频道?
我的刮刀功能如下:
func ScrapeArticle(db *sql.DB, id int64) {
// time function duration
start := time.Now()
// storedArticle contains information stored in db which need to be updated through scraping
storedArticle := getArticleById(db, id)
// init goquery
doc, err := goquery.NewDocument(storedArticle.Url.String)
glog.Info("scraping article with url --> ", storedArticle.Url.String)
if err != nil {
glog.Error("error while scraping article with id %d -- > ", storedArticle.ID, err)
return
}
// start scraping page title
doc.Find("head").Each(func(i int, s *goquery.Selection) {
pageTitle := s.Find("title").Text()
storedArticle.Name = sql.NullString{String: strings.TrimSpace(pageTitle), Valid: true}
})
// now get meta description field
doc.Find("meta").Each(func(i int, s *goquery.Selection) {
if name, _ := s.Attr("name"); strings.EqualFold(name, "description") {
description, _ := s.Attr("content")
storedArticle.Description = sql.NullString{String: strings.TrimSpace(description), Valid: true}
}
})
// if unable to scrape title, then use url
if len(storedArticle.Name.String) == 0 {
storedArticle.Name.String = storedArticle.Url.String
}
// if unable to scrape description, then use default text
if len(storedArticle.Description.String) == 0 {
storedArticle.Description.String = noDescription
}
// debugging info
glog.Infof("scraped title --> %s (length: %d)", storedArticle.Name.String, len(storedArticle.Name.String))
glog.Infof("scraped description --> %s (length: %d)", storedArticle.Description.String, len(storedArticle.Description.String))
// after succesfull scraping, add page title (and more?) to article in db
updateArticle(db, storedArticle)
elapsed := time.Since(start)
glog.Infof("scraping article %d completed in %s", storedArticle.ID.Int64, elapsed.String())
}
最佳答案
有关频道的基本和高级用法,请参见本演示文稿:http://talks.golang.org/2013/advconc.slide#1
关于go - Go例程中的 channel 使用情况,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31011234/