multiinterceptor

multiinterceptor is a simple library which provides a function to chain multiple UnaryServerInterceptors or StreamServerInterceptors for gRPC.

Usage

import (
	multiint "github.com/mercari/go-grpc-interceptor/multiinterceptor"
)

func main() {
	uIntOpt := grpc.UnaryInterceptor(multiint.NewMultiUnaryServerInterceptor(
		fooUnaryInterceptor,
		barUnaryInterceptor,
	))
	sIntOpt := grpc.StreamInterceptor(multiint.NewMultiStreamServerInterceptor(
		fooStreamInterceptor,
		barStreamInterceptor,
	))
	grpc.NewServer(uIntOpt, sIntOpt)
}

Context

Unary RPC

In unary RPC, context.Context is passed via argument from preceding interceptor or caller. And you can simply wrap context with context.WithValue and pass it to next handler.

func ExampleUnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
	newctx := context.WithValue(ctx, "some_key", "some_value")
	return handler(newctx, req)
}

Streaming RPC

In streaming RPC, context.Context is handled by grpc.ServerStream passed via argument. Call stream.Context() to get context.Context from stream. If you want to create a new context from the context, use NewServerStreamWithContext, which wraps the grpc.ServerStream with a new context. Then you pass the wrapped stream to next handler.

func ExampleStreamingInterceptor(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
	ctx := stream.Context()
	newctx := context.WithValue(ctx, "some_key", "some_value")
	newStream := multiint.NewServerStreamWithContext(stream, newctx)
	return handler(srv, newStream)
}