Use the context from the metadata if it exists

server/contextserverstream.go

@@ -0,0 +1,41 @@
+package server
+
+import (
+	"context"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+)
+
+// A gRPC server stream will only let you get its context but
+// there is no way to set a new (augmented context) to the next
+// handler (like we do for a unary request). We need to wrap the grpc.ServerSteam
+// to be able to set a new context that will be sent to the next stream interceptor.
+type contextServerStream struct {
+	ss  grpc.ServerStream
+	ctx context.Context
+}
+
+func (css *contextServerStream) SetHeader(md metadata.MD) error {
+	return css.ss.SetHeader(md)
+}
+
+func (css *contextServerStream) SendHeader(md metadata.MD) error {
+	return css.ss.SendHeader(md)
+}
+
+func (css *contextServerStream) SetTrailer(md metadata.MD) {
+	css.ss.SetTrailer(md)
+}
+
+func (css *contextServerStream) Context() context.Context {
+	return css.ctx
+}
+
+func (css *contextServerStream) SendMsg(m interface{}) error {
+	return css.ss.SendMsg(m)
+}
+
+func (css *contextServerStream) RecvMsg(m interface{}) error {
+	return css.ss.RecvMsg(m)
+}

server/interceptor.go

@@ -0,0 +1,111 @@
+package server
+
+import (
+	"context"
+	"errors"
+	"strings"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+
+	"github.com/docker/api/client"
+	"github.com/docker/api/config"
+	apicontext "github.com/docker/api/context"
+	"github.com/docker/api/context/store"
+	"github.com/docker/api/server/proxy"
+)
+
+// key is the key where the current docker context is stored in the metadata
+// of a gRPC request
+const key = "context_key"
+
+// unaryServerInterceptor configures the context and sends it to the next handler
+func unaryServerInterceptor(clictx context.Context) grpc.UnaryServerInterceptor {
+	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+		currentContext, err := getIncomingContext(ctx)
+		if err != nil {
+			currentContext, err = getConfigContext(clictx)
+			if err != nil {
+				return nil, err
+			}
+		}
+		configuredCtx, err := configureContext(clictx, currentContext, info.FullMethod)
+		if err != nil {
+			return nil, err
+		}
+
+		return handler(configuredCtx, req)
+	}
+}
+
+// streamServerInterceptor configures the context and sends it to the next handler
+func streamServerInterceptor(clictx context.Context) grpc.StreamServerInterceptor {
+	return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		currentContext, err := getIncomingContext(ss.Context())
+		if err != nil {
+			currentContext, err = getConfigContext(clictx)
+			if err != nil {
+				return err
+			}
+		}
+		ctx, err := configureContext(clictx, currentContext, info.FullMethod)
+		if err != nil {
+			return err
+		}
+
+		return handler(srv, &contextServerStream{
+			ss:  ss,
+			ctx: ctx,
+		})
+	}
+}
+
+// Returns the current context from the configuration file
+func getConfigContext(ctx context.Context) (string, error) {
+	configDir := config.Dir(ctx)
+	configFile, err := config.LoadFile(configDir)
+	if err != nil {
+		return "", err
+	}
+	return configFile.CurrentContext, nil
+}
+
+// Returns the context set by the caller if any, error otherwise
+func getIncomingContext(ctx context.Context) (string, error) {
+	if md, ok := metadata.FromIncomingContext(ctx); ok {
+		if key, ok := md[key]; ok {
+			return key[0], nil
+		}
+	}
+
+	return "", errors.New("not found")
+}
+
+// configureContext populates the request context with objects the client
+// needs: the context store and the api client
+func configureContext(ctx context.Context, currentContext string, method string) (context.Context, error) {
+	configDir := config.Dir(ctx)
+
+	ctx = apicontext.WithCurrentContext(ctx, currentContext)
+
+	// The contexts service doesn't need the client
+	if !strings.Contains(method, "/com.docker.api.protos.context.v1.Contexts") {
+		c, err := client.New(ctx)
+		if err != nil {
+			return nil, err
+		}
+
+		ctx, err = proxy.WithClient(ctx, c)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	s, err := store.New(store.WithRoot(configDir))
+	if err != nil {
+		return nil, err
+	}
+	ctx = store.WithContextStore(ctx, s)
+
+	return ctx, nil
+}

server/interceptor_test.go

@@ -0,0 +1,121 @@
+package server
+
+import (
+	"context"
+	"io/ioutil"
+	"os"
+	"path"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+
+	"github.com/docker/api/config"
+	apicontext "github.com/docker/api/context"
+)
+
+type interceptorSuite struct {
+	suite.Suite
+	dir string
+	ctx context.Context
+}
+
+func (is *interceptorSuite) BeforeTest(suiteName, testName string) {
+	dir, err := ioutil.TempDir("", "example")
+	require.Nil(is.T(), err)
+
+	ctx := context.Background()
+	ctx = config.WithDir(ctx, dir)
+	err = ioutil.WriteFile(path.Join(dir, "config.json"), []byte(`{"currentContext": "default"}`), 0644)
+	require.Nil(is.T(), err)
+
+	is.dir = dir
+	is.ctx = ctx
+}
+
+func (is *interceptorSuite) AfterTest(suiteName, tesName string) {
+	err := os.RemoveAll(is.dir)
+	require.Nil(is.T(), err)
+}
+
+func (is *interceptorSuite) TestUnaryGetCurrentContext() {
+	interceptor := unaryServerInterceptor(is.ctx)
+
+	currentContext := is.callUnary(context.Background(), interceptor)
+
+	assert.Equal(is.T(), "default", currentContext)
+}
+
+func (is *interceptorSuite) TestUnaryContextFromMetadata() {
+	contextName := "test"
+
+	interceptor := unaryServerInterceptor(is.ctx)
+	reqCtx := context.Background()
+	reqCtx = metadata.NewIncomingContext(reqCtx, metadata.MD{
+		(key): []string{contextName},
+	})
+
+	currentContext := is.callUnary(reqCtx, interceptor)
+
+	assert.Equal(is.T(), contextName, currentContext)
+}
+
+func (is *interceptorSuite) TestStreamGetCurrentContext() {
+	interceptor := streamServerInterceptor(is.ctx)
+
+	currentContext := is.callStream(context.Background(), interceptor)
+
+	assert.Equal(is.T(), "default", currentContext)
+}
+
+func (is *interceptorSuite) TestStreamContextFromMetadata() {
+	contextName := "test"
+
+	interceptor := streamServerInterceptor(is.ctx)
+	reqCtx := context.Background()
+	reqCtx = metadata.NewIncomingContext(reqCtx, metadata.MD{
+		(key): []string{contextName},
+	})
+
+	currentContext := is.callStream(reqCtx, interceptor)
+
+	assert.Equal(is.T(), contextName, currentContext)
+}
+
+func (is *interceptorSuite) callStream(ctx context.Context, interceptor grpc.StreamServerInterceptor) string {
+	currentContext := ""
+	err := interceptor(nil, &contextServerStream{
+		ctx: ctx,
+	}, &grpc.StreamServerInfo{
+		FullMethod: "/com.docker.api.protos.context.v1.Contexts/test",
+	}, func(srv interface{}, stream grpc.ServerStream) error {
+		currentContext = apicontext.CurrentContext(stream.Context())
+		return nil
+	})
+
+	require.Nil(is.T(), err)
+
+	return currentContext
+}
+
+func (is *interceptorSuite) callUnary(ctx context.Context, interceptor grpc.UnaryServerInterceptor) string {
+	currentContext := ""
+	resp, err := interceptor(ctx, nil, &grpc.UnaryServerInfo{
+		FullMethod: "/com.docker.api.protos.context.v1.Contexts/test",
+	}, func(ctx context.Context, req interface{}) (interface{}, error) {
+		currentContext = apicontext.CurrentContext(ctx)
+		return nil, nil
+	})
+
+	require.Nil(is.T(), err)
+	require.Nil(is.T(), resp)
+
+	return currentContext
+}
+
+func TestInterceptor(t *testing.T) {
+	suite.Run(t, new(interceptorSuite))
+}