使用gRPC在容器之间进行通信

Question

I'm implementing two services (server and client) running on two different containers and trying to use gRPC to communicate between them.

If I deploy the server as a container and run the client not on a container, everything works just fine. But if I deploy the client on a different container I get Error #01: could not retrieve restaurant's list: rpc error: code = Unavailable desc = grpc: the connection is unavailable error.

What steps am I missing to communicate two different containers using gRPC?

PS: I would like to try without Kubernetes for now.

SERVER

func Serve() {

    log.Println("serving...")

    port := ":50051"

    lis, err := net.Listen("tcp", port)
    if err != nil {
        log.Fatalf("failed to listen on port %s: %v", port, err)
    }

    s := grpc.NewServer()
    server := server{}
    RegisterNeo4BaconServer(s, server)

    if err := s.Serve(lis); err != nil {
        log.Fatal("could not serve: ", err)
    }
}

Makefile

image: ## build docker image and push image to registry
    @docker build -t neo4bacon -f resources/prod/Dockerfile .

run: ## deploy application container
    @docker run --rm -d --name neo4bacon neo4bacon

CLIENT

func Get() (*api.RestaurantList, error) {
    // Neo4bacon backend
    backendPort := ":50051"

    conn, err := grpc.Dial(backendPort, grpc.WithInsecure())
    if err != nil {
        &api.RestaurantList{}, fmt.Errorf("could not connect to backend %s: %s", backendPort, err)
    }
    defer conn.Close()

    client := api.NewNeo4BaconClient(conn)

    restaurantList, err := client.List(context.Background(), &api.Empty{})
    if err != nil {
        return &api.RestaurantList{}, fmt.Errorf("could not retrieve restaurant's list: %s", err)
    }
    return restaurantList, nil
}

Makefile

image: ## build docker image and push image to registry     
@docker build -t alesr/bacon-api -f resources/prod/Dockerfile .     

run: ## deploy docker container     
@docker run --rm -d -p 8080:8080 --name bacon-api bacon-api

Answer 1

You need to include the hostname in the dial function, otherwise it's looking at localhost which is unique to each container (docker creates a separate networking namespace for containers by default). Change the following:

backendPort := "neo4bacon:50051"

Edit: you also need to setup a network and connect the containers to that network because the default bridge does not include DNS discovery:

docker network create baconnet
docker run --rm -d --net baconnet --name neo4bacon neo4bacon
docker run --rm -d --net baconnet -p 8080:8080 --name bacon-api bacon-api