Golang Context.Done方法代碼示例

// ServeConn takes an inbound conn and proxies it to a backend.
func (p *ReverseProxy) ServeConn(ctx context.Context, dconn net.Conn) {
	transport := p.transport
	if transport == nil {
		panic("router: nil transport for proxy")
	}
	defer dconn.Close()

	clientGone := dconn.(http.CloseNotifier).CloseNotify()
	ctx, cancel := context.WithCancel(ctx)
	defer cancel() // finish cancellation goroutine

	go func() {
		select {
		case <-clientGone:
			cancel() // client went away, cancel request
		case <-ctx.Done():
		}
	}()

	uconn, err := transport.Connect(ctx)
	if err != nil {
		p.logf("router: proxy error: %v", err)
		return
	}
	defer uconn.Close()

	joinConns(uconn, dconn)
}

// ServeConn takes an inbound conn and proxies it to a backend.
func (p *ReverseProxy) ServeConn(ctx context.Context, dconn net.Conn) {
	transport := p.transport
	if transport == nil {
		panic("router: nil transport for proxy")
	}
	defer dconn.Close()

	clientGone := dconn.(http.CloseNotifier).CloseNotify()
	ctx, cancel := context.WithCancel(ctx)
	defer cancel() // finish cancellation goroutine

	go func() {
		select {
		case <-clientGone:
			cancel() // client went away, cancel request
		case <-ctx.Done():
		}
	}()

	l := p.Logger.New("client_addr", dconn.RemoteAddr(), "host_addr", dconn.LocalAddr(), "proxy", "tcp")

	uconn, err := transport.Connect(ctx, l)
	if err != nil {
		return
	}
	defer uconn.Close()

	joinConns(uconn, dconn)
}

func (a *aggregatorAPI) GetLog(ctx context.Context, w http.ResponseWriter, req *http.Request) {
	ctx, cancel := context.WithCancel(ctx)
	if cn, ok := w.(http.CloseNotifier); ok {
		ch := cn.CloseNotify()
		go func() {
			select {
			case <-ch:
				cancel()
			case <-ctx.Done():
			}
		}()
	}
	defer cancel()

	params, _ := ctxhelper.ParamsFromContext(ctx)

	follow := false
	if strFollow := req.FormValue("follow"); strFollow == "true" {
		follow = true
	}

	var (
		backlog bool
		lines   int
		err     error
	)
	if strLines := req.FormValue("lines"); strLines != "" {
		if lines, err = strconv.Atoi(strLines); err != nil {
			httphelper.ValidationError(w, "lines", err.Error())
			return
		}
		if lines < 0 || lines > 10000 {
			httphelper.ValidationError(w, "lines", "lines must be an integer between 0 and 10000")
			return
		}
		backlog = lines > 0
	}

	filters := make(filterSlice, 0)
	if jobID := req.FormValue("job_id"); jobID != "" {
		filters = append(filters, filterJobID(jobID))
	}
	if processTypeVals, ok := req.Form["process_type"]; ok && len(processTypeVals) > 0 {
		val := processTypeVals[len(processTypeVals)-1]
		filters = append(filters, filterProcessType(val))
	}

	iter := &Iterator{
		id:      params.ByName("channel_id"),
		follow:  follow,
		backlog: backlog,
		lines:   lines,
		filter:  filters,
		donec:   ctx.Done(),
	}

	writeMessages(ctx, w, iter.Scan(a.agg))
}

func (d *pgDataStore) Sync(ctx context.Context, h SyncHandler, startc chan<- struct{}) error {
	ctx, cancel := context.WithCancel(ctx)

	idc, errc, err := d.startListener(ctx)
	if err != nil {
		return err
	}

	initialRoutes, err := d.List()
	if err != nil {
		cancel()
		return err
	}

	toRemove := h.Current()
	for _, route := range initialRoutes {
		if _, ok := toRemove[route.ID]; ok {
			delete(toRemove, route.ID)
		}
		if err := h.Set(route); err != nil {
			return err
		}
	}
	// send remove for any routes that are no longer in the database
	for id := range toRemove {
		if err := h.Remove(id); err != nil {
			return err
		}
	}
	close(startc)

	for {
		select {
		case id := <-idc:
			if err := d.handleUpdate(h, id); err != nil {
				cancel()
				return err
			}
		case err = <-errc:
			return err
		case <-ctx.Done():
			// wait for startListener to finish (it will either
			// close idc or send an error on errc)
			select {
			case <-idc:
			case <-errc:
			}
			return nil
		}
	}
}

func dialTCP(ctx context.Context, addrs []string) (net.Conn, string, error) {
	donec := ctx.Done()
	for _, addr := range addrs {
		select {
		case <-donec:
			return nil, "", errCanceled
		default:
		}

		if conn, err := dialer.Dial("tcp", addr); err == nil {
			return conn, addr, nil
		}
	}
	return nil, "", errNoBackends
}

func dialTCP(ctx context.Context, l log15.Logger, addrs []string) (net.Conn, string, error) {
	donec := ctx.Done()
	for i, addr := range addrs {
		select {
		case <-donec:
			return nil, "", errCanceled
		default:
		}
		conn, err := dialer.Dial("tcp", addr)
		if err == nil {
			return conn, addr, nil
		}
		l.Error("retriable dial error", "backend", addr, "err", err, "attempt", i)
	}
	return nil, "", errNoBackends
}

func (d *pgDataStore) Sync(ctx context.Context, h SyncHandler, startc chan<- struct{}) error {
	ctx, cancel := context.WithCancel(ctx)

	idc, errc, err := d.startListener(ctx)
	if err != nil {
		return err
	}

	initialRoutes, err := d.List()
	if err != nil {
		cancel()
		return err
	}

	for _, route := range initialRoutes {
		if err := h.Set(route); err != nil {
			return err
		}
	}
	close(startc)

	for {
		select {
		case id := <-idc:
			if err := d.handleUpdate(h, id); err != nil {
				cancel()
				return err
			}
		case err = <-errc:
			return err
		case <-ctx.Done():
			// wait for startListener to finish (it will either
			// close idc or send an error on errc)
			select {
			case <-idc:
			case <-errc:
			}
			return nil
		}
	}
}

func writeMessages(ctx context.Context, w http.ResponseWriter, msgc <-chan *rfc5424.Message) {
	ticker := time.NewTicker(50 * time.Millisecond)
	defer ticker.Stop()

	enc := json.NewEncoder(w)
	for {
		select {
		case syslogMsg, ok := <-msgc:
			if !ok { // channel is closed / done
				return
			}
			if err := enc.Encode(NewMessageFromSyslog(syslogMsg)); err != nil {
				log15.Error("error writing msg", "err", err)
				return
			}
		case <-ticker.C:
			w.(http.Flusher).Flush()
		case <-ctx.Done():
			return
		}
	}
}

func (d *pgDataStore) startListener(ctx context.Context) (<-chan string, <-chan error, error) {
	idc := make(chan string)
	errc := make(chan error)

	conn, err := d.pgx.Acquire()
	if err != nil {
		return nil, nil, err
	}
	if err = conn.Listen(d.tableName); err != nil {
		d.pgx.Release(conn)
		return nil, nil, err
	}

	go func() {
		defer unlistenAndRelease(d.pgx, conn, d.tableName)
		defer close(idc)

		for {
			select {
			case <-ctx.Done():
				return
			default:
			}
			notification, err := conn.WaitForNotification(time.Second)
			if err == pgx.ErrNotificationTimeout {
				continue
			}
			if err != nil {
				errc <- err
				return
			}

			idc <- notification.Payload
		}
	}()

	return idc, errc, nil
}

func (a *aggregatorAPI) GetLog(ctx context.Context, w http.ResponseWriter, req *http.Request) {
	ctx, cancel := context.WithCancel(ctx)
	if cn, ok := w.(http.CloseNotifier); ok {
		go func() {
			select {
			case <-cn.CloseNotify():
				cancel()
			case <-ctx.Done():
			}
		}()
	}
	defer cancel()

	params, _ := ctxhelper.ParamsFromContext(ctx)
	channelID := params.ByName("channel_id")

	follow := false
	if strFollow := req.FormValue("follow"); strFollow == "true" {
		follow = true
	}

	lines := -1 // default to all lines
	if strLines := req.FormValue("lines"); strLines != "" {
		var err error
		lines, err = strconv.Atoi(strLines)
		if err != nil || lines < 0 || lines > 10000 {
			httphelper.ValidationError(w, "lines", "lines must be an integer between 0 and 10000")
			return
		}
	}

	filters := make(filterSlice, 0)
	if jobID := req.FormValue("job_id"); jobID != "" {
		filters = append(filters, filterJobID(jobID))
	}
	if processTypeVals, ok := req.Form["process_type"]; ok && len(processTypeVals) > 0 {
		val := processTypeVals[len(processTypeVals)-1]
		filters = append(filters, filterProcessType(val))
	}

	w.WriteHeader(200)

	var msgc <-chan *rfc5424.Message
	if follow {
		msgc = a.agg.ReadLastNAndSubscribe(channelID, lines, filters, ctx.Done())
	} else {
		msgc = a.agg.ReadLastN(channelID, lines, filters, ctx.Done())
	}
	writeMessages(ctx, w, msgc)
}

func (c *controllerAPI) AppLog(ctx context.Context, w http.ResponseWriter, req *http.Request) {
	ctx, cancel := context.WithCancel(ctx)

	opts := logaggc.LogOpts{
		Follow: req.FormValue("follow") == "true",
		JobID:  req.FormValue("job_id"),
	}
	if vals, ok := req.Form["process_type"]; ok && len(vals) > 0 {
		opts.ProcessType = &vals[len(vals)-1]
	}
	if strLines := req.FormValue("lines"); strLines != "" {
		lines, err := strconv.Atoi(req.FormValue("lines"))
		if err != nil {
			respondWithError(w, err)
			return
		}
		opts.Lines = &lines
	}
	rc, err := c.logaggc.GetLog(c.getApp(ctx).ID, &opts)
	if err != nil {
		respondWithError(w, err)
		return
	}

	if cn, ok := w.(http.CloseNotifier); ok {
		go func() {
			select {
			case <-cn.CloseNotify():
				rc.Close()
			case <-ctx.Done():
			}
		}()
	}
	defer cancel()
	defer rc.Close()

	if !strings.Contains(req.Header.Get("Accept"), "text/event-stream") {
		w.Header().Set("Content-Type", "text/plain")
		w.WriteHeader(200)
		// Send headers right away if following
		if wf, ok := w.(http.Flusher); ok && opts.Follow {
			wf.Flush()
		}

		fw := httphelper.FlushWriter{Writer: w, Enabled: opts.Follow}
		io.Copy(fw, rc)
		return
	}

	ch := make(chan *sseLogChunk)
	l, _ := ctxhelper.LoggerFromContext(ctx)
	s := sse.NewStream(w, ch, l)
	defer s.Close()
	s.Serve()

	msgc := make(chan *json.RawMessage)
	go func() {
		defer close(msgc)
		dec := json.NewDecoder(rc)
		for {
			var m json.RawMessage
			if err := dec.Decode(&m); err != nil {
				if err != io.EOF {
					l.Error("decoding logagg stream", err)
				}
				return
			}
			msgc <- &m
		}
	}()

	for {
		select {
		case m := <-msgc:
			if m == nil {
				ch <- &sseLogChunk{Event: "eof"}
				return
			}
			// write to sse
			select {
			case ch <- &sseLogChunk{Event: "message", Data: *m}:
			case <-s.Done:
				return
			case <-ctx.Done():
				return
			}
		case <-s.Done:
			return
		case <-ctx.Done():
			return
		}
	}
}

func (a *aggregatorAPI) GetLog(ctx context.Context, w http.ResponseWriter, req *http.Request) {
	ctx, cancel := context.WithCancel(ctx)
	if cn, ok := w.(http.CloseNotifier); ok {
		go func() {
			select {
			case <-cn.CloseNotify():
				cancel()
			case <-ctx.Done():
			}
		}()
	}
	defer cancel()

	params, _ := ctxhelper.ParamsFromContext(ctx)
	channelID := params.ByName("channel_id")

	follow := false
	if strFollow := req.FormValue("follow"); strFollow == "true" {
		follow = true
	}

	lines := -1 // default to all lines
	if strLines := req.FormValue("lines"); strLines != "" {
		var err error
		lines, err = strconv.Atoi(strLines)
		if err != nil || lines < 0 || lines > 10000 {
			httphelper.ValidationError(w, "lines", "lines must be an integer between 0 and 10000")
			return
		}
	}

	filters := make([]filter, 0)
	if strJobID := req.FormValue("job_id"); strJobID != "" {
		filters = append(filters, filterJobID{[]byte(strJobID)})
	}
	if processTypeVals, ok := req.Form["process_type"]; ok && len(processTypeVals) > 0 {
		val := processTypeVals[len(processTypeVals)-1]
		filters = append(filters, filterProcessType{[]byte(val)})
	}

	w.WriteHeader(200)

	var msgc <-chan *rfc5424.Message
	if follow {
		msgc = a.agg.ReadLastNAndSubscribe(channelID, lines, filters, ctx.Done())
		go flushLoop(w.(http.Flusher), 50*time.Millisecond, ctx.Done())
	} else {
		msgc = a.agg.ReadLastN(channelID, lines, filters, ctx.Done())
	}

	enc := json.NewEncoder(w)
	for {
		select {
		case syslogMsg := <-msgc:
			if syslogMsg == nil { // channel is closed / done
				return
			}
			if err := enc.Encode(NewMessageFromSyslog(syslogMsg)); err != nil {
				log15.Error("error writing msg", "err", err)
				return
			}
		case <-ctx.Done():
			return
		}
	}
}