Running the Ruby Bookshelf on Kubernetes Engine

This tutorial shows how to run the Ruby Bookshelf Application on Kubernetes Engine. Follow this tutorial to containerize and deploy an existing Ruby web application to Kubernetes Engine. It is highly recommended that you work through the Bookshelf app documentation as part of the tutorial for the App Engine flexible environment.

Objectives

  • Create a Kubernetes Engine cluster.
  • Containerize a Ruby application.
  • Create a replicated frontend for the Bookshelf application.
  • Create a replicated backend for the Bookshelf application.
  • Create a load-balanced service to route HTTP traffic to the Bookshelf frontend.

Costs

This tutorial uses billable components of Cloud Platform, including:

  • Kubernetes Engine
  • Compute Engine
  • Cloud Storage
  • Cloud Datastore
  • Cloud Pub/Sub

Use the Pricing Calculator to generate a cost estimate based on your projected usage. New GCP users might be eligible for a free trial.

Before you begin

  1. Sign in to your Google Account.

    If you don't already have one, sign up for a new account.

  2. Select or create a GCP project.

    Go to the Manage resources page

  3. Make sure that billing is enabled for your project.

    Learn how to enable billing

  4. Enable the Cloud Datastore, Cloud Storage, Cloud Pub/Sub, and Google+ APIs.

    Enable the APIs

  5. Install and initialize the Cloud SDK.
  6. Install Docker. Docker is used to build container images locally.
  7. Install kubectl:
    gcloud components install kubectl

Creating a Kubernetes Engine cluster

A Kubernetes Engine cluster is a managed set of Compute Engine virtual machines that operate as a single Kubernetes cluster. This tutorial needs a cluster with a minimum of two nodes, and these nodes need access to all Google APIs. Replace [YOUR_GCP_ZONE] with the Cloud Platform zone where you want your cluster to be hosted.

  1. Create the cluster:

    gcloud container clusters create bookshelf \
        --scopes "cloud-platform,userinfo-email" \
        --num-nodes 2 \
        --enable-basic-auth \
        --issue-client-certificate \
        --enable-ip-alias \
        --zone [YOUR_GCP_ZONE]
    
  2. Verify that you have access to the cluster:

    kubectl get nodes
    

    Running this command lists the nodes in your container cluster and indicates that your container cluster is up and running and you have access to it.

You use the kubectl command to create resources in a Kubernetes Engine Cluster. To learn more about kubectl, see Kubernetes Engine Cluster Operations. In general, you use gcloud to manage resources in your GCP project and you use kubectl to manage resources within your Kubernetes Engine cluster. A single project can have multiple clusters, which makes it easy to have clusters that are made up of different machine types to satisfy different needs.

When you create a cluster with gcloud, it automatically sets up authentication for kubectl. Clusters created by using the Cloud Console can set up authentication using the gcloud container clusters get-credentials command.

Cloning the sample application

The sample application is available on GitHub at GoogleCloudPlatform/getting-started-ruby.

  1. Clone the repository:

    git clone https://github.com/GoogleCloudPlatform/getting-started-ruby.git
    
  2. Navigate to the sample directory:

    cd getting-started-ruby/optional-kubernetes-engine
    

Initializing Datastore

The Bookshelf application uses Cloud Datastore to store the books. To initialize Datastore in your project for the first time:

  1. Open the Datastore on GCP Console.

  2. Select a region for your datastore and click Continue. When you reach the “Create an Entity” page, close the window as the Bookshelf application is ready to create entities on Datastore.

Creating a Cloud Storage bucket

The Bookshelf application uses Google Cloud Storage to store image files.

The following instructions show how to create a Cloud Storage bucket. Buckets are the basic containers that hold your data in Cloud Storage.

To create a bucket:

  1. Invoke the following command in a terminal window:

    gsutil mb gs://[YOUR-BUCKET-NAME]

  2. Set the bucket's default ACL to public-read, which enables users to see their uploaded images:

    gsutil defacl set public-read gs://[YOUR-BUCKET-NAME]

Creating a Cloud Pub/Sub topic and subscription

The Bookshelf application uses Cloud Pub/Sub for a background processing queue of requests to get data from the Google Books API for a book added to the Bookshelf.

  1. Create a new Cloud Pub/Sub topic using the following Cloud SDK command:

    gcloud pubsub topics create [YOUR_PUBSUB_TOPIC]
    
  2. Create a new Cloud Pub/Sub subscription for the topic created in the prior step using the following command:

    gcloud pubsub subscriptions create --topic [YOUR_PUBSUB_TOPIC] [YOU_PUBSUB_SUBSCRIPTION]
    

Configuring the application

  1. Copy the example configuration files to create your customized versions. These are in .gitignore and will not be committed to version control.

    cp config/database.example.yml config/database.yml
    cp config/settings.example.yml config/settings.yml
    
  2. Open config/database.yml for editing.

  3. Replace [YOUR_PROJECT_ID] with your project ID.
  4. Open config/settings.yml for editing.
  5. Replace:

    • [YOUR_PROJECT_ID] with your project ID.
    • [YOUR_PUBSUB_TOPIC] with your Cloud Pub/Sub topic.
    • [YOUR_PUBSUB_SUBSCRIPTION] with your Cloud Pub/Sub subscription.
    • [YOUR_BUCKET_NAME] with the name of the bucket you created in the previous step.
    • [YOUR_CLIENT_ID] with your OAuth client id.
    • [YOUR_CLIENT_SECRET] with your OAuth client secret.

Containerizing the application

The sample application includes a Dockerfile, which is used create the application's Docker image. This Docker image runs the application on Kubernetes Engine.

# The Google App Engine Ruby runtime is Debian Jessie with Ruby installed
# and various os-level packages to allow installation of popular Ruby
# gems. The source is on github at:
#   https://github.com/GoogleCloudPlatform/ruby-docker
FROM gcr.io/google_appengine/ruby

# Install 2.4.3 if not already preinstalled by the base image
RUN cd /rbenv/plugins/ruby-build && \
    git pull && \
    rbenv install -s 2.4.3 && \
    rbenv global 2.4.3 && \
    gem install -q --no-rdoc --no-ri bundler --version 1.16.1
ENV RBENV_VERSION 2.4.3

# Copy the application files.
COPY . /app/

# Install required gems.
RUN bundle install --deployment && rbenv rehash

# Set environment variables.
ENV RACK_ENV=production \
    RAILS_ENV=production \
    RAILS_SERVE_STATIC_FILES=true

# Run asset pipeline.
RUN bundle exec rake assets:precompile

# Reset entrypoint to override base image.
ENTRYPOINT []

# Use foreman to start processes. $FORMATION will be set in the pod
# manifest. Formations are defined in Procfile.
CMD bundle exec foreman start --formation "$FORMATION"
The sample application also includes a .dockerignore file that lists filepaths that aren't included in the resulting Docker container. Typically, this includes build artifacts and local dependency installations.

# Copyright 2015, Google, Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

.git
log/*
tmp/*

Build the application's Docker image:

docker build -t gcr.io/[YOUR_PROJECT_ID]/bookshelf .

Push the image to Google Container Registry so that your cluster can access the image:

gcloud docker -- push gcr.io/[YOUR_PROJECT_ID]/bookshelf

Deploying the Bookshelf front end

The Bookshelf application has a frontend server that handles the web requests and a backend worker that processes books and adds additional information.

The cluster resources needed to run the frontend are defined in bookshelf-frontend.yaml. These resources are described as a Kubernetes Deployment. Deployments make it easy to create and update a replica set and its associated pods.

# Copyright 2016, Google, Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# This file configures the bookshelf application frontend. The frontend serves
# public web traffic.

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: bookshelf-frontend
  labels:
    app: bookshelf
    tier: frontend
# The bookshelf frontend replica set ensures that at least 3
# instances of the bookshelf app are running on the cluster.
# For more info about Pods see:
#   https://cloud.google.com/kubernetes-engine/docs/pods/
spec:
  replicas: 3
  template:
    metadata:
      labels:
        app: bookshelf
        tier: frontend
    spec:
      containers:
      - name: bookshelf-app
        # Replace [YOUR_PROJECT_ID] with your project ID.
        image: gcr.io/[YOUR_PROJECT_ID]/bookshelf:latest
        # This setting makes nodes pull the docker image every time before
        # starting the pod. This is useful when debugging, but should be turned
        # off in production.
        imagePullPolicy: Always
        # The FORMATION environment variable is used by foreman in the
        # Dockerfile's CMD to control which processes are started. In this
        # case, only the bookshelf process is needed.
        env:
        - name: FORMATION
          value: web=1
        # The bookshelf process listens on port 8080 for web traffic by default.
        ports:
        - name: http-server
          containerPort: 8080
  1. In bookshelf-frontend.yaml, replace [YOUR_PROJECT_ID] with your project ID.
  2. Use kubectl to deploy the resources to the cluster:

    kubectl create -f bookshelf-frontend.yaml
    
  3. Track the status of the deployment:

    kubectl get deployments
    

    Once the deployment has the same number of available pods as desired pods, the deployment is complete. If you run into issues with the deployment, you can delete it and start over:

    kubectl delete deployments bookshelf-frontend
    
  4. Once the deployment is complete you can see the pods that the deployment created:

    kubectl get pods
    

Deploying the Bookshelf back end

The Bookshelf back end is deployed the same way as the frontend.

# Copyright 2016, Google, Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# This file configures the bookshelf worker. The worker processes
# jobs in the background.

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: bookshelf-worker
  labels:
    app: bookshelf
    tier: worker
# The bookshelf worker replica set ensures that at least 2
# instances of the bookshelf worker are running on the cluster.
# For more info about Pods see:
#   https://cloud.google.com/kubernetes-engine/docs/pods/
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: bookshelf
        tier: worker
    spec:
      containers:
      - name: bookshelf-worker
        # Replace [YOUR_PROJECT_ID] with your project ID.
        image: gcr.io/[YOUR_PROJECT_ID]/bookshelf:latest
        # This setting makes nodes pull the docker image every time before
        # starting the pod. This is useful when debugging, but should be turned
        # off in production.
        imagePullPolicy: Always
        # The FORMATION environment variable is used by foreman in the
        # Dockerfile's CMD to control which processes are started. In this
        # case, only the worker process is needed.
        env:
        - name: FORMATION
          value: worker=1
  1. In bookshelf-worker.yaml, replace [YOUR_PROJECT_ID] with your project ID.
  2. Use kubectl to deploy the resources to the cluster:

    kubectl create -f bookshelf-worker.yaml
    
  3. Verify that the pods are running:

    kubectl get pods
    

Creating the Bookshelf service

Kubernetes Services provide a single point of access to a set of pods. While it's possible to access a single pod, pods are ephemeral and it's usually more convenient to address a set of pods with a single endpoint. In the Bookshelf application, The Bookshelf service allows you to access the Bookshelf frontend pods from a single IP address. This service is defined in bookshelf-service.yaml

# Copyright 2016, Google, Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# The bookshelf service provides a load-balancing proxy over the bookshelf
# frontend pods. By specifying the type as a 'LoadBalancer', Kubernetes Engine
# will create an external HTTP load balancer.
# For more information about Services see:
#   https://cloud.google.com/kubernetes-engine/docs/services/
# For more information about external HTTP load balancing see:
#   https://cloud.google.com/kubernetes-engine/docs/load-balancer
apiVersion: v1
kind: Service
metadata:
  name: bookshelf-frontend
  labels:
    app: bookshelf
    tier: frontend
spec:
  type: LoadBalancer
  ports:
  - port: 80
    targetPort: http-server
  selector:
    app: bookshelf
    tier: frontend

Notice that the pods and the service that uses the pods are separate. Kubernetes uses labels to select the pods that a service addresses. With labels, you can have a service that addresses pods from different replica sets and have multiple services that point to an individual pod.

  1. Create the Bookshelf service:

    kubectl create -f bookshelf-service.yaml
    
  2. Get the service's external IP address:

    kubectl describe service bookshelf
    

    Note that it may take up to 60 seconds for the IP address to be allocated. The external IP address will be listed under LoadBalancer Ingress.

Accessing the Bookshelf application

You have now deployed all the resources needed to run the Bookshelf application on Kubernetes Engine. Use the external IP address from the previous step to load the application in your web browser and create books. If you deployed the worker, the books are automatically updated with information from the Google Books API.

Cleaning up

To avoid incurring charges to your Google Cloud Platform account for the resources used in this tutorial:

Deleting the project

The easiest way to eliminate billing is to delete the project you created for the tutorial.

To delete the project:

  1. In the GCP Console, go to the Projects page.

    Go to the Projects page

  2. In the project list, select the project you want to delete and click Delete project. After selecting the checkbox next to the project name, click
      Delete project
  3. In the dialog, type the project ID, and then click Shut down to delete the project.

Deleting the cluster

Deleting the cluster removes all Kubernetes Engine and Compute Engine resources, but you need to manually remove any resources in Cloud Storage, Cloud Datastore, and Cloud Pub/Sub.

Delete the cluster using the following command. Replace [YOUR_GCP_ZONE] with the zone you used when creating the cluster.

gcloud container clusters delete bookshelf --zone [YOUR_GCP_ZONE]

What's next

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