net & http & timeout

net & http & timeout ===   > [name=郭學聰 Hsueh-Tsung Kuo] > [time=Sun, 02 Aug 2020] [color=red] ###### CC BY-SA 4.0 ---  ## Who am I? ![fieliapm](https://www.gravatar.com/avatar/2aef78f04240a6ac9ccd473ba1cbd1e3?size=2048 =384x384) Someone (who?) said: a game programmer should be able to draw cute anime character(?) ----  * A programmer from game company in Taiwan * Backend (and temporary frontend) engineer, focus on common service * Usually develop something related to my work in Python, Ruby, ECMAScript, Golang, C# * ECMAScript hater since **Netscape** is dead ----  * Built CDN-aware game asset update system * Built almost entire VOEZ game server by myself only * Supported Sdorica backend development * Verify and tweak Soul of Eden backend performance ---  ## Outline ----  4. net/http 5. net/http Timeout * Reason * Spec * Server * Client 6. Streaming & Timeout 7. Implementation 8. Timer Issues 9. Conclusion 10. Reference 11. Q&A ---  ## net/http ----  ### Information https://golang.org/pkg/net/http/ ----  ### Feature * HTTP * Client * Server * Hijack * WebSocket ---  ## net/http Timeout ----  ### Reason Leak File Descriptors ``` http: Accept error: accept tcp [::]:80: accept4: too many open files; retrying in 5ms ``` ----  ### Reason Slowloris https://en.wikipedia.org/wiki/Slowloris_(computer_security) ----  ### Spec The complete guide to Go net/http timeouts https://blog.cloudflare.com/the-complete-guide-to-golang-net-http-timeouts/ ----  #### Server ![http server timeout](https://blog.cloudflare.com/content/images/2016/06/Timeouts-001.png) ----  ##### Phase Timeout ```go= srv := &http.Server{ ReadTimeout: 5 * time.Second, WriteTimeout: 10 * time.Second, IdleTimeout: 60 * time.Second, ReadHeaderTimeout: 1 * time.Second, } log.Println(srv.ListenAndServe()) ``` ----  #### Client ![http client timeout](https://blog.cloudflare.com/content/images/2016/06/Timeouts-002.png) ----  ##### Entire Timeout ```go= c := &http.Client{ Timeout: 15 * time.Second, } resp, err := c.Get("https://blog.filippo.io/") ``` ----  ##### Phase Timeout ```go= c := &http.Client{ Transport: &http.Transport{ Dial: (&net.Dialer{ Timeout: 30 * time.Second, KeepAlive: 30 * time.Second, }).Dial, TLSHandshakeTimeout: 10 * time.Second, ResponseHeaderTimeout: 10 * time.Second, ExpectContinueTimeout: 1 * time.Second, IdleConnTimeout: 60 * time.Second, } } ``` ---  ## Streaming & Timeout ----  ### Phase Timeout ![http server timeout](https://blog.cloudflare.com/content/images/2016/06/Timeouts-001.png =738x216) ![http client timeout](https://blog.cloudflare.com/content/images/2016/06/Timeouts-002.png =745x201) ----  ### Streaming Timeout net/http: no way of manipulating timeouts in Handler #16100 https://github.com/golang/go/issues/16100 ----  ### Streaming Timeout per Entrypoint # It does not exist! ----  #### Game Over? * Good Game... GG * 人生ｵﾜﾀ＼(^ o ^)／ # :shit: :shit: :shit: ----  #### Open Source # Do It Yourself ---  ## Implementation ----  ### fieliapm/stream-http-go * Repository * https://github.com/fieliapm/stream-http-go * GoDoc * https://godoc.org/github.com/fieliapm/stream-http-go/pkg/stream_http ----  #### Client ----  ##### Client Example ```go= ctx := context.Background() client := http.DefaultClient requestMod := stream_http.RequestMod(func(req *http.Request) { req.Header.Set("Content-Type", "application/x-www-form-urlencoded") req.Header.Set("Authorization", "Bearer qawsedrftgyhujikolp") query := req.URL.Query() query.Add("param", "pvalue") req.URL.RawQuery = query.Encode() }) requestTimeout := stream_http.Timeout(500 * time.Millisecond) reqBody := bytes.NewBuffer([]byte("form=fvalue")) var respBody bytes.Buffer resp, err := stream_http.DoRequest(ctx, client, http.MethodPost, "http://httpbin.org/anything", reqBody, &respBody, requestMod, requestTimeout) //resp, err := stream_http.DoRequest(ctx, client, http.MethodGet, "http://httpbin.org/status/401", nil, &respBody, requestMod, requestTimeout) if err != nil { return err } fmt.Printf("get response with status code: %d\n%s\n", resp.StatusCode, respBody.String()) ``` ----  ##### Spirit * context :arrow_forward: context, cancel() * :warning: timeout event :arrow_right: cancel() * :heavy_check_mark: chunk transmitted :arrow_right: reset timeout  ----  ##### Client Control Flow ```graphviz digraph client_control_flow { nodesep=1.0 // increases the separation between nodes node [color="hotpink" shape=box] edge [color="hotpink" style=dashed] with_cancel [shape="oval" label="context.WithCancel()"] context_parent [label="parent context"] context [label="context"] cancel [color="gray" label="cancel()"] client_do [shape="oval" label="client.Do()"] timer [shape="oval" label="time.AfterFunc()"] context_parent->with_cancel [style=solid] with_cancel->context [style=solid] with_cancel->cancel [style=solid] cancel->context [color="gray"] context->client_do [style=solid] timer->cancel [color="orange"] } ``` ----  #### Server ----  ##### Server Example ```go= func handleFunc(w http.ResponseWriter, req *http.Request) { n, err := stream_http.TimeoutCopy(&reqBody, req.Body, time.Duration(-1), 500*time.Millisecond) n, err = stream_http.TimeoutCopy(w, &respBody, 500*time.Millisecond, time.Duration(-1)) } ``` ----  ##### Spirit * TimeoutCopy() :arrow_forward: copy goroutine * :heavy_check_mark: chunk transmitted :arrow_right: reset timeout  * :warning: timeout event :arrow_right: TimeoutCopy()  * TimeoutCopy() :arrow_right: :x: copy goroutine  ----  ##### Server Handle Flow ```sequence note left of handler: receive request handler->TimeoutCopy(): call TimeoutCopy()->runtimeTimer: time.NewTimer() TimeoutCopy()->copy goroutine: request/response_writer note right of copy goroutine: chunk transmitted copy goroutine->runtimeTimer: timer.Reset()/timer.Stop() note right of copy goroutine: copy finished copy goroutine->TimeoutCopy(): copyResult/panic TimeoutCopy()->handler: copy result note left of handler: send ok/error response note right of runtimeTimer: timeout runtimeTimer->TimeoutCopy(): timer.C TimeoutCopy()->handler: error timeout TimeoutCopy()->copy goroutine: close(doneChan) note left of handler: send timeout response ``` ----  ##### Question How to correctly stop server handler? ----  ##### Answer # I don't know ¯\\\_(ツ)\_/¯ ---  ## Timer Issues ----  time: Timer.C can still trigger even after Timer.Reset is called #11513 https://github.com/golang/go/issues/11513 ----  Timer.Reset() note https://golang.org/pkg/time/#Timer.Reset Reset should be invoked only on stopped or expired timers with drained channels. If a program has already received a value from t.C, the timer is known to have expired and the channel drained, so t.Reset can be used directly. If a program has not yet received a value from t.C, however, the timer must be stopped and—if Stop reports that the timer expired before being stopped—the channel explicitly drained: ```go= if !t.Stop() { <-t.C } t.Reset(d) ``` This should not be done concurrent to other receives from the Timer's channel. ----  time: Timer.Reset is not possible to use correctly #14038 https://github.com/golang/go/issues/14038 ----  Timer.Reset() note https://golang.org/pkg/time/#Timer.Reset Note that it is not possible to use Reset's return value correctly, as there is a race condition between draining the channel and the new timer expiring. Reset should always be invoked on stopped or expired channels, as described above. The return value exists to preserve compatibility with existing programs. ----  ### Understand Timer Behaviour ```go= if !t.Stop() { <-t.C // don't do this if t.C is drained from another goroutine } _ = t.Reset(d) // don't use return value ``` ----  ### Broken Timer Implementation * Go version * go \< 1.8 :arrow_right: crap  * go \>= 1.8 (added note) :arrow_right: crap  ----  ### History Repeats Itself * time: Timer.C can still trigger even after Timer.Reset is called #11513 * time: Timer.Reset is not possible to use correctly #14038 * ... ... ----  ![Georg Wilhelm Friedrich Hegel](https://upload.wikimedia.org/wikipedia/commons/b/bf/1831_Schlesinger_Philosoph_Georg_Friedrich_Wilhelm_Hegel_anagoria.JPG =379x480) Georg Wilhelm Friedrich Hegel https://de.wikipedia.org/wiki/Georg_Wilhelm_Friedrich_Hegel ----  > Was die Erfahrung aber und die Geschichte lehren, ist dieses, daß **Völker und Regierungen niemals etwas aus der Geschichte gelernt** und nach Lehren, die aus derselben zu ziehen gewesen wären, gehandelt haben. > [name=Georg Wilhelm Friedrich Hegel] :dizzy: ----  > We learn from history that **we do not learn from history**. > [name=Georg Wilhelm Friedrich Hegel] ---  ## Conclusion ----  ### Contribute! * fieliapm/stream-http-go * Better client interface * Server side timeout handling example * How to correctly stop server handler > [name=郭學聰 Hsueh-Tsung Kuo] [time=2020_08_02] [color=red] :notebook: ---  ## Reference ----  ### Blog * The complete guide to Go net/http timeouts \[en\] * https://blog.cloudflare.com/the-complete-guide-to-golang-net-http-timeouts/ * How to use timer reset in Golang correctly \[zh\] * https://tonybai.com/2016/12/21/how-to-use-timer-reset-in-golang-correctly/ ---  ## Q&A --- <style> .reveal { background: #FFDFEF; 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