README.md

Example of gRPC service on Python with minikube and knative

Service is a simple greeter taken from official gRPC examples.

Start minikube cluster and install knative:

minikube start --driver=virtualbox
../knative_install.sh

Run from sources

python3.8 -m venv .venv
source .venv/bin/activate
pip install grpcio protobuf
python greeter_server.py

# from another terminal:
python greeter_client.py localhost:50051
Greeter client received: Hello, you!  # <-- it works
Greeter client received: Hello again, you!  # <-- it works

Run from docker image

docker build -t grpc_greeter:v0 .
docker run --rm -d -p 50051:50051 --name grpc_greeter grpc_greeter:v0
python greeter_client.py localhost:50051
Greeter client received: Hello, you!  # <-- it works
Greeter client received: Hello again, you!  # <-- it works
docker stop grpc_greeter

Run as plain kubernetes service

eval $(minikube -p minikube docker-env)
docker build -t grpc_greeter:v0 .
kubectl apply -f service_plain.yaml
export GREETER_PORT=$(kubectl get services/grpc-greeter-service -o go-template='{{(index .spec.ports 0).nodePort}}')
python greeter_client.py $(minikube ip):$GREETER_PORT
Greeter client received: Hello, you!  # <-- it works
Greeter client received: Hello again, you!  # <-- it works
kubectl delete -f service_plain.yaml

Run as knative service

eval $(minikube -p minikube docker-env)
docker build -t dev.local/grpc_greeter:v0 .
# Tags resolution should be disabled for dev.local, see ../README.md
kubectl apply -f service_knative.yaml

kubectl get service
NAME                         TYPE           CLUSTER-IP       EXTERNAL-IP                        PORT(S)                             AGE
grpc-greeter                 ExternalName   <none>           grpc-greeter.default.example.com   <none>                              117s
grpc-greeter-k2l9v           ClusterIP      10.101.146.238   <none>                             80/TCP                              118s
grpc-greeter-k2l9v-private   ClusterIP      10.101.122.58    <none>                             80/TCP,9090/TCP,9091/TCP,8022/TCP   118s
kubernetes                   ClusterIP      10.96.0.1        <none>                             443/TCP                             4d1h

kubectl get service -n kong
NAME                      TYPE           CLUSTER-IP       EXTERNAL-IP   PORT(S)                      AGE
kong-proxy                LoadBalancer   10.98.127.254    <pending>     80:32188/TCP,443:32637/TCP   4d1h

Test with python client

python greeter_client_knative.py $(minikube ip):32188

Doesn't work. Python gRPC API is not working through proxy because we can't provide additional headers to gRPC call. Additional "Host" header is required to allow kong-proxy resolving to what service it should requrect a request. There is also something called :authority pseudoheader (whatever it means) in HTTP/2 seemingly allowing the same behaviour. Python guys seem not very interesting in fixing this issues as there were two PRs in python gRPC repo providing authority and host params, but both of them were closed without merging.