grproxy

GRPC proxy to inspect, record, and reply requests

When you are debugging an issue, some time you want to know what is the GRPC client (eg: frontend application) is sending and what the server (eg: backend application) sent back to the client. Normally This would involve putting log or print statement in both side. With grproxy you can inspect the wire to see what actually being sent and received without changing the applications.

Current limitations

Only support inspecting request and response
Stream request/response is not logged
Server needs to implement reflection API

Planned for the future

Support recording the request to a file which can be used later on to simulate the request in a different machine (eg: local dev laptop) multiple times.
Filter on specific methods
Reading the schema from a proto files definition

Running

$ ./grproxy -addr "127.0.0.1:9999" -target "127.0.0.1:10000"

Arguments

addr local address of the proxy
target upstream (backend) of the GRPC server to forward to

Running with docker

$ docker run --rm -it -p 9999:9999 yulrizka/grproxy:latest -target "host.docker.internal:10000"

host.docker.internal will be translated by Docker to the host IP address as a workaround since OSX or Windows does not support --net=host. This is if you bind remote GRPC server to your local machine (localhost). See example below.

Example

Say that you are running a GRPC service FooService on remote kubernetes port 10000.

To debug it, first you need to forward the grpc service port to localhost

$ kubectl port-forward svc/foo-service 10000:10000

At this point you will have the original GRPC server running on port 10000 locally.

Start the proxy on port 9999

$ docker run --rm -it -p 9999:9999 yulrizka/grproxy:latest -target "host.docker.internal:10000"

This will open the proxy on port 9999 on your local (host) machine that forward the request to localhost:10000 which eventually forward the request to the original (upstream) GRPC server.

In your app, you can start using the proxy as GRPC server.

# example listing all methods with grpcurl
$ grpcurl -plaintext localhost:9999 list

Fooservice
grpc.reflection.v1alpha.ServerReflection


# example calling a method (on a separate terminal)
$ echo '{"id":1}' | grpcurl -d @ -plaintext localhost:9999 Fooservice.GetUser

# output of the proxy
Fooservice.GetUser
{
  "id": "1"
}

response:
{
    "id": "1",
    "Name": "Jhon Doe"
}