enhance: add preseed and caching for metadata

runner/data.go

@@ -59,6 +59,7 @@ type dataProvider struct {
 
 type mdProvider struct {
 	metadata []byte
+	preseed  metadata.MD
 }
 
 func newDataProvider(mtd *desc.MethodDescriptor,
@@ -215,11 +216,34 @@ func (dp *dataProvider) getMessages(ctd *CallData, i int, inputData []byte) ([]*
 	return inputs, nil
 }
 
-func newMetadataProvider(mtd *desc.MethodDescriptor, metadata []byte) (*mdProvider, error) {
-	return &mdProvider{metadata: metadata}, nil
+func newMetadataProvider(mtd *desc.MethodDescriptor, mdData []byte) (*mdProvider, error) {
+	// Test if we can preseed data
+	ctd := newCallData(mtd, nil, "", 0)
+	ha, err := ctd.hasAction(string(mdData))
+	if err != nil {
+		return nil, err
+	}
+
+	var preseed metadata.MD = nil
+	if !ha {
+		mdMap, err := ctd.executeMetadata(string(mdData))
+		if err != nil {
+			return nil, err
+		}
+
+		if len(mdMap) > 0 {
+			preseed = metadata.New(mdMap)
+		}
+	}
+
+	return &mdProvider{metadata: mdData, preseed: preseed}, nil
 }
 
 func (dp *mdProvider) getMetadataForCall(ctd *CallData) (*metadata.MD, error) {
+	if dp.preseed != nil {
+		return &dp.preseed, nil
+	}
+
 	mdMap, err := ctd.executeMetadata(string(dp.metadata))
 	if err != nil {
 		return nil, err

runner/data_test.go

@@ -265,3 +265,83 @@ func TestData_createPayloads(t *testing.T) {
 		assert.Len(t, inputs, 0)
 	})
 }
+
+func TestMetadata_newMetadataProvider(t *testing.T) {
+	t.Run("no action", func(t *testing.T) {
+		mtdUnary, err := protodesc.GetMethodDescFromProto(
+			"helloworld.Greeter.SayHello",
+			"../testdata/greeter.proto",
+			nil)
+		assert.NoError(t, err)
+
+		mdp, err := newMetadataProvider(mtdUnary, []byte(`{"token":"asdf"}`))
+		assert.NoError(t, err)
+		assert.NotNil(t, mdp)
+		assert.NotNil(t, mdp.preseed)
+		assert.Equal(t, []string{"asdf"}, mdp.preseed.Get("token"))
+	})
+
+	t.Run("with action", func(t *testing.T) {
+		mtdUnary, err := protodesc.GetMethodDescFromProto(
+			"helloworld.Greeter.SayHello",
+			"../testdata/greeter.proto",
+			nil)
+		assert.NoError(t, err)
+
+		mdp, err := newMetadataProvider(mtdUnary, []byte(`{"token":"{{ .RequestNumber }}"}`))
+		assert.NoError(t, err)
+		assert.NotNil(t, mdp)
+		assert.Nil(t, mdp.preseed)
+	})
+}
+
+func TestMetadata_getMetadataForCall(t *testing.T) {
+	t.Run("no action", func(t *testing.T) {
+		mtdUnary, err := protodesc.GetMethodDescFromProto(
+			"helloworld.Greeter.SayHello",
+			"../testdata/greeter.proto",
+			nil)
+		assert.NoError(t, err)
+
+		mdp, err := newMetadataProvider(mtdUnary, []byte(`{"token":"asdf"}`))
+		assert.NoError(t, err)
+		assert.NotNil(t, mdp.preseed)
+
+		cd := newCallData(mtdUnary, nil, "123", 1)
+
+		md, err := mdp.getMetadataForCall(cd)
+		assert.NoError(t, err)
+		assert.NotNil(t, md)
+		assert.Equal(t, []string{"asdf"}, md.Get("token"))
+		assert.Same(t, &mdp.preseed, md)
+	})
+
+	t.Run("with action", func(t *testing.T) {
+		mtdUnary, err := protodesc.GetMethodDescFromProto(
+			"helloworld.Greeter.SayHello",
+			"../testdata/greeter.proto",
+			nil)
+		assert.NoError(t, err)
+
+		mdp, err := newMetadataProvider(mtdUnary, []byte(`{"token":"{{ .RequestNumber }}"}`))
+		assert.NoError(t, err)
+		assert.Nil(t, mdp.preseed)
+
+		cd := newCallData(mtdUnary, nil, "123", 1)
+
+		md1, err := mdp.getMetadataForCall(cd)
+		assert.NoError(t, err)
+		assert.NotNil(t, md1)
+		assert.Equal(t, []string{"1"}, md1.Get("token"))
+		assert.NotSame(t, mdp.preseed, md1)
+
+		cd = newCallData(mtdUnary, nil, "123", 2)
+		md2, err := mdp.getMetadataForCall(cd)
+		assert.NoError(t, err)
+		assert.NotNil(t, md2)
+		assert.Equal(t, []string{"2"}, md2.Get("token"))
+		assert.NotSame(t, mdp.preseed, md2)
+		assert.NotSame(t, md1, md2)
+		assert.NotEqual(t, md1, md2)
+	})
+}