Yet another gRPC echo server

YAGES (yet another gRPC echo server) is an educational gRPC server implementation. The goal is to learn gRPC and communicate best practices around its deployment and usage in the context of Kubernetes.

• As an Kubernetes app
  • From inside the cluster
  • From outside the cluster
• As a local app
  • Install
  • Use
  • Develop

As an Kubernetes app

You can install YAGES as an app in your Kubernetes cluster (tested with Kubernetes v1.9, v1.10, and v1.11) like so:

$ kubectl apply -f http://mhausenblas.info/yages/app.yaml

Then, in order to invoke the service you've got essentially two options: from inside the cluster or from the outside the cluster, by exposing the service.

From inside the cluster

To access the gRPC server from inside the cluster, you can for example use the gump container image that has grpcurl installed:

$ kubectl run -it --rm grpcurl --restart=Never --image=quay.io/mhausenblas/gump:0.1 -- sh 
If you don't see a command prompt, try pressing enter.
/go $ grpcurl --plaintext yages:9000 yages.Echo.Ping
{
  "text": "pong"
}

From outside the cluster

TBD: Using Ingress as shown in ingress.yaml or an OpenShift Route object with TLS passthrough set.

As a local app

Install

Requires Go 1.9 or above, do:

$ go get -u github.com/mhausenblas/yages

Use

You can run go run main.go in $GOPATH/src/github.com/mhausenblas/yages or if you've added $GOPATH/bin to your path, directly call the binary:

$ yages
2018/03/25 16:23:42 YAGES in version dev serving on 0.0.0.0:9000 is ready for gRPC clients …

Open up a second terminal session and using grpcurl execute the following:

# invoke the ping method:
$ grpcurl --plaintext localhost:9000 yages.Echo.Ping
{
  "text": "pong"
}
# invoke the reverse method with parameter:
$ grpcurl --plaintext -d '{ "text" : "some fun here" }' localhost:9000 yages.Echo.Reverse
{
  "text": "ereh nuf emos"
}
# invoke the reverse method with parameter from JSON file:
$ cat echo.json | grpcurl --plaintext -d @ localhost:9000 yages.Echo.Reverse
{
  "text": "ohce"
}

Note that you can execute grpcurl --plaintext localhost:9000 list and grpcurl --plaintext localhost:9000 describe to get further details on the available services and their respective methods.

Develop

First you want to generate the stubs based on the protobuf schema. Note that this requires the Go gRPC runtime and plug-in installed on your machine, including protoc in v3 set up, see grpc.io for the steps.

Do the following:

$ protoc \
  --proto_path=$GOPATH/src/github.com/mhausenblas/yages \
  --go_out=plugins=grpc:yages \
  yages-schema.proto

Executing above command results in the auto-generated file yages/yages-schema.pb.go. Do not manually edit this file, or put in other words: if you add a new message or service to the schema defined in yages-schema.proto just run above protoc command again and you'll get an updated version of yages-schema.pb.go in the yages/ directory as a result.