endpoints: add gRPC getting started sample (#217)

The gRPC code is based off gRPC's hello world:
https://github.com/grpc/grpc-go/tree/master/examples/helloworld

endpoints/getting-started-grpc/Dockerfile

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+FROM golang:alpine
+
+RUN apk update \
+  && apk add git
+
+COPY . /go/src/app
+
+# Don't do this in production! Use vendoring instead.
+RUN go get -v app/server
+
+RUN go install app/server
+
+ENTRYPOINT ["/go/bin/server"]

endpoints/getting-started-grpc/README.md

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+# Google Cloud Endpoints Sample for Go using gRPC
+
+This sample demonstrates how to use Google Cloud Endpoints using Go and gRPC.
+
+For a complete walkthrough, see the following guides:
+
+* [Quickstart with gRPC on Container Engine](https://cloud.google.com/endpoints/docs/quickstart-grpc-container-engine)
+* [Quickstart with gRPC on Compute Engine](https://cloud.google.com/endpoints/docs/quickstart-grpc-compute-engine-docker)
+
+## Test the code locally (optional)
+
+Run the backend using `go run`:
+
+```bash
+$ go run server/main.go
+```
+
+Send a request from another terminal:
+
+```bash
+$ go run client/main.go
+2017/03/30 17:08:32 Greeting: Hello world
+```
+
+## Deploying service config
+
+1. First, generate `out.pb` from the proto file:
+
+    ```bash
+    protoc --include_imports --include_source_info helloworld/helloworld.proto --descriptor_set_out out.pb
+    ```
+
+1. Edit `api_config.yaml`. Replace `YOUR_PROJECT_ID`:
+
+    ```yaml
+    name: hellogrpc.endpoints.YOUR_PROJECT_ID.cloud.goog
+    ```
+
+1. Deploy your service:
+
+    ```bash
+    gcloud service-management deploy out.pb api_config.yaml
+    ```
+
+    Your config ID should be printed out, it looks like `2017-03-30r0`.
+    Take a note of it, you'll need it later.
+
+    You can list the config IDs using this command:
+
+    ```bash
+    gcloud service-management configs list --service hellogrpc.endpoints.YOUR_PROJECT_ID.cloud.goog
+    ```
+
+## Building the server's Docker container
+
+Build and tag your gRPC server, storing it in your private container registry:
+
+```bash
+gcloud container builds submit --tag gcr.io/YOUR_PROJECT_ID/go-grpc-hello:1.0 .
+```
+
+## Deploy to GCE or GKE
+
+### Deploy to GCE
+
+1. Create an instance and SSH into it:
+
+    ```bash
+    gcloud compute instances create grpc-host --image-family gci-stable --image-project google-containers --tags=http-server
+    gcloud compute ssh grpc-host
+    ```
+
+1. Set some environment variables (you'll need to manually set the service config ID):
+
+    ```bash
+    GCLOUD_PROJECT=$(curl -s "http://metadata.google.internal/computeMetadata/v1/project/project-id" -H "Metadata-Flavor: Google")
+    SERVICE_NAME=hellogrpc.endpoints.${GCLOUD_PROJECT}.cloud.goog
+    SERVICE_CONFIG_ID=<Your Config ID>
+    ```
+
+1. Pull your credentials to access your private container registry:
+
+    ```bash
+    /usr/share/google/dockercfg_update.sh
+    ```
+
+1. Run your gRPC server's container:
+
+    ```bash
+    docker run -d --name=grpc-hello gcr.io/${GCLOUD_PROJECT}/go-grpc-hello:1.0
+    ```
+
+1. Run Endpoints proxy:
+
+    ```bash
+    docker run --detach --name=esp \
+        -p 80:9000 \
+        --link=grpc-hello:grpc-hello \
+        gcr.io/endpoints-release/endpoints-runtime:1 \
+        -s ${SERVICE_NAME} \
+        -v ${SERVICE_CONFIG_ID} \
+        -P 9000 \
+        -a grpc://grpc-hello:50051
+    ```
+
+1. Get the IP address of your secured gRPC server:
+
+    ```bash
+    gcloud compute instances list --filter=grpc-host
+    ```
+
+1. Send a request to the API server (see "Running the client" below)
+
+### Deploy to GKE
+
+If you haven't got a cluster, first [create one](https://cloud.google.com/container-engine/docs/clusters/operations).
+
+1. Edit `container-engine.yaml`. Replace `<YOUR_PROJECT_ID>` and `<SERVICE_CONFIG_ID>`.
+
+1. Create the deployment and service:
+
+    ```
+    kubectl apply -f container-engine.yaml
+    ```
+
+1. Wait until the load balancer is active:
+
+    ```
+    kubectl get svc grpc-hello --watch
+    ```
+
+1. Send a request to the API server (see "Running the client" below)
+
+## Running the client
+
+1. First, [create a project API key](https://console.developers.google.com/apis/credentials).
+
+1. Then, after you have your server's IP address (via GKE's `kubectl get svc` or your GCE instance's IP), run:
+
+    ```bash
+    go run client/main.go -api-key=AIza.... -addr=YOUR_SERVER_IP_ADDRESS:80 [message]
+    ```
+
+[1]: https://cloud.google.com/endpoints/docs/quickstarts

endpoints/getting-started-grpc/api_config.yaml

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+# An example API configuration.
+#
+# Below, replace YOUR_PROJECT_ID with your Google Cloud Project ID.
+
+# The configuration schema is defined by service.proto file
+# https://github.com/googleapis/googleapis/blob/master/google/api/service.proto
+type: google.api.Service
+config_version: 3
+
+# Name of the service configuration.
+name: hellogrpc.endpoints.YOUR_PROJECT_ID.cloud.goog
+
+# API title to appear in the user interface (Google Cloud Console).
+title: Hello gRPC API
+apis:
+- name: helloworld.Greeter

endpoints/getting-started-grpc/client/main.go

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+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package main
+
+import (
+	"flag"
+	"log"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+	pb "google.golang.org/grpc/examples/helloworld/helloworld"
+	"google.golang.org/grpc/metadata"
+)
+
+const defaultName = "world"
+
+var (
+	addr = flag.String("addr", "127.0.0.1:50051", "Address of grpc server.")
+	key  = flag.String("api-key", "", "API key.")
+)
+
+func main() {
+	flag.Parse()
+
+	// Set up a connection to the server.
+	conn, err := grpc.Dial(*addr, grpc.WithInsecure())
+	if err != nil {
+		log.Fatalf("did not connect: %v", err)
+	}
+	defer conn.Close()
+	c := pb.NewGreeterClient(conn)
+
+	ctx := context.Background()
+	ctx = metadata.NewContext(ctx, metadata.Pairs("x-api-key", *key))
+
+	// Contact the server and print out its response.
+	name := defaultName
+	if len(flag.Args()) > 0 {
+		name = flag.Arg(0)
+	}
+	r, err := c.SayHello(ctx, &pb.HelloRequest{Name: name})
+	if err != nil {
+		log.Fatalf("could not greet: %v", err)
+	}
+	log.Printf("Greeting: %s", r.Message)
+}

endpoints/getting-started-grpc/container-engine.yaml

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+apiVersion: v1
+kind: Service
+metadata:
+  name: grpc-hello
+spec:
+  ports:
+  - port: 80
+    targetPort: 9000
+    protocol: TCP
+    name: http
+  selector:
+    app: grpc-hello
+  type: LoadBalancer
+---
+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: grpc-hello
+spec:
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        app: grpc-hello
+    spec:
+      containers:
+      - name: esp
+        image: gcr.io/endpoints-release/endpoints-runtime:1
+        args: [
+          "-P", "9000",
+          "-a", "grpc://127.0.0.1:50051",
+          "-s", "hellogrpc.endpoints.<YOUR_PROJECT_ID>.cloud.goog", # replace <YOUR_PROJECT_ID>
+          "-v", "<SERVICE_CONFIG_ID>", # e.g. "2017-03-30r0"
+        ]
+        ports:
+          - containerPort: 9000
+      - name: echo
+        image: gcr.io/<YOUR_PROJECT_ID>/go-grpc-hello:1.0 # replace <YOUR_PROJECT_ID>
+        ports:
+          - containerPort: 50051