Add support for request timeout propgation.

Adds a new field to the `Request` type which specifies a timeout (in
nanoseconds) for the request. This is propagated on method dispatch as a
context timeout.

There was some discussion here on supporting a broader "metadata" field
(similar to grpc) that can be used for other things, but we ended up
with a dedicated field because it is lighter weight and expect it to be
used pretty heavily as is.... metadata may be added in the future, but
is not necessary for timeouts.

Also discussed using a deadline vs a timeout in the request and decided
to go with a timeout in order to deal with potential clock skew between
the client and server. This also has the side-effect of eliminating the
protocol/wire overhead from the request timeout.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

client.go

@@ -24,6 +24,7 @@ import (
 	"strings"
 	"sync"
 	"syscall"
+	"time"
 
 	"github.com/gogo/protobuf/proto"
 	"github.com/pkg/errors"
@@ -86,6 +87,10 @@ func (c *Client) Call(ctx context.Context, service, method string, req, resp int
 		cresp = &Response{}
 	)
 
+	if dl, ok := ctx.Deadline(); ok {
+		creq.TimeoutNano = dl.Sub(time.Now()).Nanoseconds()
+	}
+
 	if err := c.dispatch(ctx, creq, cresp); err != nil {
 		return err
 	}
@@ -104,6 +109,7 @@ func (c *Client) Call(ctx context.Context, service, method string, req, resp int
 func (c *Client) dispatch(ctx context.Context, req *Request, resp *Response) error {
 	errs := make(chan error, 1)
 	call := &callRequest{
+		ctx:  ctx,
 		req:  req,
 		resp: resp,
 		errs: errs,

server.go

@@ -414,6 +414,9 @@ func (c *serverConn) run(sctx context.Context) {
 		case request := <-requests:
 			active++
 			go func(id uint32) {
+				ctx, cancel := getRequestContext(ctx, request.req)
+				defer cancel()
+
 				p, status := c.server.services.call(ctx, request.req.Service, request.req.Method, request.req.Payload)
 				resp := &Response{
 					Status:  status.Proto(),
@@ -454,3 +457,15 @@ func (c *serverConn) run(sctx context.Context) {
 		}
 	}
 }
+
+var noopFunc = func() {}
+
+func getRequestContext(ctx context.Context, req *Request) (retCtx context.Context, cancel func()) {
+	cancel = noopFunc
+	if req.TimeoutNano == 0 {
+		return ctx, cancel
+	}
+
+	ctx, cancel = context.WithTimeout(ctx, time.Duration(req.TimeoutNano))
+	return ctx, cancel
+}

server_test.go

@@ -24,6 +24,7 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"time"
 
 	"github.com/gogo/protobuf/proto"
 	"github.com/pkg/errors"
@@ -57,7 +58,8 @@ func (tc *testingClient) Test(ctx context.Context, req *testPayload) (*testPaylo
 }
 
 type testPayload struct {
-	Foo string `protobuf:"bytes,1,opt,name=foo,proto3"`
+	Foo      string `protobuf:"bytes,1,opt,name=foo,proto3"`
+	Deadline int64  `protobuf:"varint,2,opt,name=deadline,proto3"`
 }
 
 func (r *testPayload) Reset()         { *r = testPayload{} }
@@ -68,7 +70,11 @@ func (r *testPayload) ProtoMessage()  {}
 type testingServer struct{}
 
 func (s *testingServer) Test(ctx context.Context, req *testPayload) (*testPayload, error) {
-	return &testPayload{Foo: strings.Repeat(req.Foo, 2)}, nil
+	tp := &testPayload{Foo: strings.Repeat(req.Foo, 2)}
+	if dl, ok := ctx.Deadline(); ok {
+		tp.Deadline = dl.UnixNano()
+	}
+	return tp, nil
 }
 
 // registerTestingService mocks more of what is generated code. Unlike grpc, we
@@ -376,6 +382,34 @@ func TestUnixSocketHandshake(t *testing.T) {
 	}
 }
 
+func TestServerRequestTimeout(t *testing.T) {
+	var (
+		ctx, cancel     = context.WithDeadline(context.Background(), time.Now().Add(10*time.Minute))
+		server          = mustServer(t)(NewServer())
+		addr, listener  = newTestListener(t)
+		testImpl        = &testingServer{}
+		client, cleanup = newTestClient(t, addr)
+		result          testPayload
+	)
+	defer cancel()
+	defer cleanup()
+	defer listener.Close()
+
+	registerTestingService(server, testImpl)
+
+	go server.Serve(ctx, listener)
+	defer server.Shutdown(ctx)
+
+	if err := client.Call(ctx, serviceName, "Test", &testPayload{}, &result); err != nil {
+		t.Fatalf("unexpected error making call: %v", err)
+	}
+
+	dl, _ := ctx.Deadline()
+	if result.Deadline != dl.UnixNano() {
+		t.Fatalf("expected deadline %v, actual: %v", dl, result.Deadline)
+	}
+}
+
 func BenchmarkRoundTrip(b *testing.B) {
 	var (
 		ctx             = context.Background()

types.go

@@ -23,9 +23,10 @@ import (
 )
 
 type Request struct {
-	Service string `protobuf:"bytes,1,opt,name=service,proto3"`
+	Service     string `protobuf:"bytes,1,opt,name=service,proto3"`
-	Method  string `protobuf:"bytes,2,opt,name=method,proto3"`
+	Method      string `protobuf:"bytes,2,opt,name=method,proto3"`
-	Payload []byte `protobuf:"bytes,3,opt,name=payload,proto3"`
+	Payload     []byte `protobuf:"bytes,3,opt,name=payload,proto3"`
+	TimeoutNano int64  `protobuf:"varint,4,opt,name=timeout_nano,proto3"`
 }
 
 func (r *Request) Reset()         { *r = Request{} }