Function NewHTTP2Client

internal/transport/http2_client.go:210–488

NewHTTP2Client constructs a connected ClientTransport to addr based on HTTP2 and starts to receive messages on it. Non-nil error returns if construction fails.

(connectCtx, ctx context.Context, addr resolver.Address, opts ConnectOptions, onClose OnCloseFunc)

// and starts to receive messages on it. Non-nil error returns if construction
// fails.
func NewHTTP2Client(connectCtx, ctx context.Context, addr resolver.Address, opts ConnectOptions, onClose OnCloseFunc) (_ ClientTransport, err error) {
	scheme := "http"
	ctx, cancel := context.WithCancel(ctx)
	defer func() {
		if err != nil {
			cancel()
		}
	}()

	// gRPC, resolver, balancer etc. can specify arbitrary data in the
	// Attributes field of resolver.Address, which is shoved into connectCtx
	// and passed to the dialer and credential handshaker. This makes it possible for
	// address specific arbitrary data to reach custom dialers and credential handshakers.
	connectCtx = icredentials.NewClientHandshakeInfoContext(connectCtx, credentials.ClientHandshakeInfo{Attributes: addr.Attributes})

	conn, err := dial(connectCtx, opts.Dialer, addr, opts.UserAgent)
	if err != nil {
		if opts.FailOnNonTempDialError {
			return nil, connectionErrorf(isTemporary(err), err, "transport: error while dialing: %v", err)
		}
		return nil, connectionErrorf(true, err, "transport: Error while dialing: %v", err)
	}

	// Any further errors will close the underlying connection
	defer func(conn net.Conn) {
		if err != nil {
			conn.Close()
		}
	}(conn)

	// The following defer and goroutine monitor the connectCtx for cancellation
	// and deadline.  On context expiration, the connection is hard closed and
	// this function will naturally fail as a result.  Otherwise, the defer
	// waits for the goroutine to exit to prevent the context from being
	// monitored (and to prevent the connection from ever being closed) after
	// returning from this function.
	ctxMonitorDone := grpcsync.NewEvent()
	newClientCtx, newClientDone := context.WithCancel(connectCtx)
	defer func() {
		newClientDone()         // Awaken the goroutine below if connectCtx hasn't expired.
		<-ctxMonitorDone.Done() // Wait for the goroutine below to exit.
	}()
	go func(conn net.Conn) {
		defer ctxMonitorDone.Fire() // Signal this goroutine has exited.
		<-newClientCtx.Done()       // Block until connectCtx expires or the defer above executes.
		if err := connectCtx.Err(); err != nil {
			// connectCtx expired before exiting the function.  Hard close the connection.
			if logger.V(logLevel) {
				logger.Infof("Aborting due to connect deadline expiring: %v", err)
			}
			conn.Close()
		}
	}(conn)

	kp := opts.KeepaliveParams
	// Validate keepalive parameters.
	if kp.Time == 0 {
		kp.Time = defaultClientKeepaliveTime