1.go test命令是一个按照约定和组织进行测试的程序
2.竞争检查器 go run -race 附带一个运行期对共享变量访问工具的test,出现WARNING: DATA RACE 说明有数据竞争3.理想情况下是应该避免掉多余的工作的,称为duplicate suppression(重复抑制/避免) 4.设计并发,不重复,无阻塞 cache 1.并发: go func(){}()直接启动新的goroutine来实现 2.并发安全:使用sync.Mutex 互斥锁来实现 3.无阻塞:get之前锁定,赋值一个入口指针后立马解锁,然后进行http请求,这样不会被慢的http请求阻塞住 4.不重复:利用channel,多个并发同时写的时候,利用channel阻塞住,等第一个请求完写完后关闭channel,其他goroutine直接请求package mainimport ( "fmt" "golang.org/x/net/html" "io/ioutil" "log" "net/http" "sync" "time")// 定义类型Memotype Memo struct { f Func mu sync.Mutex cache map[string]*entry}type Func func(key string) (interface{}, error)type result struct { value interface{} err error}type entry struct { res result ready chan struct{} // closed when res is ready}func main() { //res, _ := httpGetBody("http://www.baidu.com") //fmt.Println(string(res.([]byte))) //类型断言 //初始化 m := New(httpGetBody) urls, _ := Extract("http://www.baidu.com") var n sync.WaitGroup for _, url := range urls { n.Add(1) go func(url string) { fmt.Println(url) start := time.Now() value, err := m.Get(url) if err != nil { log.Print(err) } if value != nil { fmt.Printf("%s, %s, %d bytes\n", url, time.Since(start), len(value.([]byte))) } n.Done() }(url) } n.Wait()}//初始化Memo类型func New(f Func) *Memo { return &Memo{f: f, cache: make(map[string]*entry)}}//获取数据放入缓存,如果缓存存在直接返回func (memo *Memo) Get(key string) (interface{}, error) { memo.mu.Lock() e := memo.cache[key] if e == nil { e = &entry{ready: make(chan struct{})} memo.cache[key] = e memo.mu.Unlock() //最耗时的函数部分没有锁,性能会提升 e.res.value, e.res.err = memo.f(key) close(e.ready) } else { memo.mu.Unlock() <-e.ready } return e.res.value, e.res.err}//获取http get数据func httpGetBody(url string) (interface{}, error) { resp, err := http.Get(url) if err != nil { return nil, err } defer resp.Body.Close() return ioutil.ReadAll(resp.Body)}func Extract(url string) ([]string, error) { resp, err := http.Get(url) if err != nil { return nil, err } if resp.StatusCode != http.StatusOK { resp.Body.Close() return nil, fmt.Errorf("getting %s: %s", url, resp.Status) } doc, err := html.Parse(resp.Body) resp.Body.Close() if err != nil { return nil, fmt.Errorf("parsing %s as HTML: %v", url, err) } var links []string visitNode := func(n *html.Node) { if n.Type == html.ElementNode && n.Data == "a" { for _, a := range n.Attr { if a.Key != "href" { continue } link, err := resp.Request.URL.Parse(a.Val) if err != nil { continue // ignore bad URLs } links = append(links, link.String()) } } } forEachNode(doc, visitNode, nil) return links, nil}func forEachNode(n *html.Node, pre, post func(n *html.Node)) { if pre != nil { pre(n) } for c := n.FirstChild; c != nil; c = c.NextSibling { forEachNode(c, pre, post) } if post != nil { post(n) }}