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      How To Migrate a Docker Compose Workflow for Rails Development to Kubernetes


      Introduction

      When building modern, stateless applications, containerizing your application’s components is the first step in deploying and scaling on distributed platforms. If you have used Docker Compose in development, you will have modernized and containerized your application by:

      • Extracting necessary configuration information from your code.
      • Offloading your application’s state.
      • Packaging your application for repeated use.

      You will also have written service definitions that specify how your container images should run.

      To run your services on a distributed platform like Kubernetes, you will need to translate your Compose service definitions to Kubernetes objects. This will allow you to scale your application with resiliency. One tool that can speed up the translation process to Kubernetes is kompose, a conversion tool that helps developers move Compose workflows to container orchestrators like Kubernetes or OpenShift.

      In this tutorial, you will translate Compose services to Kubernetes objects using kompose. You will use the object definitions that kompose provides as a starting point and make adjustments to ensure that your setup will use Secrets, Services, and PersistentVolumeClaims in the way that Kubernetes expects. By the end of the tutorial, you will have a single-instance Rails application with a PostgreSQL database running on a Kubernetes cluster. This setup will mirror the functionality of the code described in Containerizing a Ruby on Rails Application for Development with Docker Compose and will be a good starting point to build out a production-ready solution that will scale with your needs.

      Prerequisites

      Step 1 — Installing kompose

      To begin using kompose, navigate to the project’s GitHub Releases page, and copy the link to the current release (version 1.22.0 as of this writing). Paste this link into the following curl command to download the latest version of kompose:

      • curl -L https://github.com/kubernetes/kompose/releases/download/v1.22.0/kompose-linux-amd64 -o kompose

      For details about installing on non-Linux systems, please refer to the installation instructions.

      Make the binary executable:

      Move it to your PATH:

      • sudo mv ./kompose /usr/local/bin/kompose

      To verify that it has been installed properly, you can do a version check:

      If the installation was successful, you will see output like the following:

      Output

      1.22.0 (955b78124)

      With kompose installed and ready to use, you can now clone the Node.js project code that you will be translating to Kubernetes.

      Step 2 — Cloning and Packaging the Application

      To use our application with Kubernetes, we will need to clone the project code and package the application so that the kubelet service can pull the image.

      Our first step will be to clone the rails-sidekiq repository from the DigitalOcean Community GitHub account. This repository includes the code from the setup described in Containerizing a Ruby on Rails Application for Development with Docker Compose, which uses a demo Rails application to demonstrate how to set up a development environment using Docker Compose. You can find more information about the application itself in the series Rails on Containers.

      Clone the repository into a directory called rails_project:

      • git clone https://github.com/do-community/rails-sidekiq.git rails_project

      Navigate to the rails_project directory:

      Now checkout the code for this tutorial from the compose-workflow branch:

      • git checkout compose-workflow

      Output

      Branch 'compose-workflow' set up to track remote branch 'compose-workflow' from 'origin'. Switched to a new branch 'compose-workflow'

      The rails_project directory contains files and directories for a shark information application that works with user input. It has been modernized to work with containers: sensitive and specific configuration information has been removed from the application code and refactored to be injected at runtime, and the application’s state has been offloaded to a PostgreSQL database.

      For more information about designing modern, stateless applications, please see Architecting Applications for Kubernetes and Modernizing Applications for Kubernetes.

      The project directory includes a Dockerfile with instructions for building the application image. Let’s build the image now so that you can push it to your Docker Hub account and use it in your Kubernetes setup.

      Using the docker build command, build the image with the -t flag, which allows you to tag it with a memorable name. In this case, tag the image with your Docker Hub username and name it rails-kubernetes or a name of your own choosing:

      • docker build -t your_dockerhub_user/rails-kubernetes .

      The . in the command specifies that the build context is the current directory.

      It will take a minute or two to build the image. Once it is complete, check your images:

      You will see the following output:

      Output

      REPOSITORY TAG IMAGE ID CREATED SIZE your_dockerhub_user/rails-kubernetes latest 24f7e88b6ef2 2 days ago 606MB alpine latest d6e46aa2470d 6 weeks ago 5.57MB

      Next, log in to the Docker Hub account you created in the prerequisites:

      • docker login -u your_dockerhub_user

      When prompted, enter your Docker Hub account password. Logging in this way will create a ~/.docker/config.json file in your user’s home directory with your Docker Hub credentials.

      Push the application image to Docker Hub with the docker push command. Remember to replace your_dockerhub_user with your own Docker Hub username:

      • docker push your_dockerhub_user/rails-kubernetes

      You now have an application image that you can pull to run your application with Kubernetes. The next step will be to translate your application service definitions to Kubernetes objects.

      Step 3 — Translating Compose Services to Kubernetes Objects with kompose

      Our Docker Compose file, here called docker-compose.yml, lays out the definitions that will run our services with Compose. A service in Compose is a running container, and service definitions contain information about how each container image will run. In this step, we will translate these definitions to Kubernetes objects by using kompose to create yaml files. These files will contain specs for the Kubernetes objects that describe their desired state.

      We will use these files to create different types of objects: Services, which will ensure that the Pods running our containers remain accessible; Deployments, which will contain information about the desired state of our Pods; a PersistentVolumeClaim to provision storage for our database data; a ConfigMap for environment variables injected at runtime; and a Secret for our application’s database user and password. Some of these definitions will be in the files kompose will create for us, and others we will need to create ourselves.

      First, we will need to modify some of the definitions in our docker-compose.yml file to work with Kubernetes. We will include a reference to our newly-built application image in our app service definition and remove the bind mounts, volumes, and additional commands that we used to run the application container in development with Compose. Additionally, we’ll redefine both containers’ restart policies to be in line with the behavior Kubernetes expects.

      If you have followed the steps in this tutorial and checked out the compose-workflow branch with git, then you should have a docker-compose.yml file in your working directory.

      If you don’t have a docker-compose.yml then be sure to visit the previous tutorial in this series, Containerizing a Ruby on Rails Application for Development with Docker Compose, and paste the contents from the linked section into a new docker-compose.yml file.

      Open the file with nano or your favorite editor:

      The current definition for the app application service looks like this:

      ~/rails_project/docker-compose.yml

      . . .
      services:
        app:
          build:
            context: .
            dockerfile: Dockerfile
          depends_on:
            - database
            - redis
          ports:
            - "3000:3000"
          volumes:
            - .:/app
            - gem_cache:/usr/local/bundle/gems
            - node_modules:/app/node_modules
          env_file: .env
          environment:
            RAILS_ENV: development
      . . .
      

      Make the following edits to your service definition:

      • Replace the build: line with image: your_dockerhub_user/rails-kubernetes
      • Remove the following context: ., and dockerfile: Dockerfile lines.
      • Remove the volumes list.

      The finished service definition will now look like this:

      ~/rails_project/docker-compose.yml

      . . .
      services:
        app:
          image: your_dockerhub_user/rails-kubernetes
          depends_on:
            - database
            - redis
          ports:
            - "3000:3000"
          env_file: .env
          environment:
            RAILS_ENV: development
      . . .
      

      Next, scroll down to the database service definition and make the following edits:

      • Remove the - ./init.sql:/docker-entrypoint-initdb.d/init.sql volume line. Instead of using values from the local SQL file, we will pass the values for our POSTGRES_USER and POSTGRES_PASSWORD to the database container using the Secret we will create in Step 4.
      • Add a ports: section that will make PostgreSQL available inside your Kubernetes cluster on port 5432.
      • Add an environment: section with a PGDATA variable that points to a directory inside /var/lib/postgresql/data. This setting is required when PostgreSQL is configured to use block storage, since the database engine expects to find its data files in a sub-directory.

      The database service definition should look like this when you are finished editing it:

      ~/rails_project/docker-compose.yml

      . . .
        database:
          image: postgres:12.1
          volumes:
            - db_data:/var/lib/postgresql/data
          ports:
            - "5432:5432"
          environment:
            PGDATA: /var/lib/postgresql/data/pgdata
      . . .
      

      Next, edit the redis service definition to expose its default TCP port by adding a ports: section with the default 6379 port. Adding the ports: section will make Redis available inside your Kubernetes cluster. Your edited redis service should resemble the following:

      ~/rails_project/docker-compose.yml

      . . .
        redis:
          image: redis:5.0.7
          ports:
            - "6379:6379"
      

      After editing the redis section of the file, continue to the sidekiq service definition. Just as with the app service, you’ll need to switch from building a local docker image to pulling from Docker Hub. Make the following edits to your sidekiq service definition:

      • Replace the build: line with image: your_dockerhub_user/rails-kubernetes
      • Remove the following context: ., and dockerfile: Dockerfile lines.
      • Remove the volumes list.

      ~/rails_project/docker-compose.yml

      . . .
        sidekiq:
          image: your_dockerhub_user/rails-kubernetes
          depends_on:
            - app
            - database
            - redis
          env_file: .env
          environment:
              RAILS_ENV: development
          entrypoint: ./entrypoints/sidekiq-entrypoint.sh
      

      Finally, at the bottom of the file, remove the gem_cache and node_modules volumes from the top-level volumes key. The key will now look like this:

      ~/rails_project/docker-compose.yml

      . . .
      volumes:
        db_data:
      

      Save and close the file when you are finished editing.

      For reference, your completed docker-compose.yml file should contain the following:

      ~/rails_project/docker-compose.yml

      version: '3'
      
      services:
        app:
          image: your_dockerhub_user/rails-kubernetes
          depends_on:
              - database
              - redis
          ports:
              - "3000:3000"
          env_file: .env
          environment:
              RAILS_ENV: development
      
        database:
          image: postgres:12.1
          volumes:
              - db_data:/var/lib/postgresql/data
          ports:
              - "5432:5432"
          environment:
              PGDATA: /var/lib/postgresql/data/pgdata
      
        redis:
          image: redis:5.0.7
          ports:
              - "6379:6379"
      
        sidekiq:
          image: your_dockerhub_user/rails-kubernetes
          depends_on:
              - app
              - database
              - redis
          env_file: .env
          environment:
              RAILS_ENV: development
          entrypoint: ./entrypoints/sidekiq-entrypoint.sh
      
      volumes:
        db_data:
      

      Before translating our service definitions, we will need to write the .env file that kompose will use to create the ConfigMap with our non-sensitive information. Please see Step 2 of Containerizing a Ruby on Rails Application for Development with Docker Compose for a longer explanation of this file.

      In that tutorial, we added .env to our .gitignore file to ensure that it would not copy to version control. This means that it did not copy over when we cloned the rails-sidekiq repository in Step 2 of this tutorial. We will therefore need to recreate it now.

      Create the file:

      kompose will use this file to create a ConfigMap for our application. However, instead of assigning all of the variables from the app service definition in our Compose file, we will only add settings for the PostgreSQL and Redis. We will assign the database name, username, and password separately when we manually create a Secret object in Step 4.

      Add the following port and database name information to the .env file. Feel free to rename your database if you would like:

      ~/rails_project/.env

      DATABASE_HOST=database
      DATABASE_PORT=5432
      REDIS_HOST=redis
      REDIS_PORT=6379
      

      Save and close the file when you are finished editing.

      You are now ready to create the files with your object specs. kompose offers multiple options for translating your resources. You can:

      • Create yaml files based on the service definitions in your docker-compose.yml file with kompose convert.
      • Create Kubernetes objects directly with kompose up.
      • Create a Helm chart with kompose convert -c.

      For now, we will convert our service definitions to yaml files and then add to and revise the files that kompose creates.

      Convert your service definitions to yaml files with the following command:

      After you run this command, kompose will output information about the files it has created:

      Output

      INFO Kubernetes file "app-service.yaml" created INFO Kubernetes file "database-service.yaml" created INFO Kubernetes file "redis-service.yaml" created INFO Kubernetes file "app-deployment.yaml" created INFO Kubernetes file "env-configmap.yaml" created INFO Kubernetes file "database-deployment.yaml" created INFO Kubernetes file "db-data-persistentvolumeclaim.yaml" created INFO Kubernetes file "redis-deployment.yaml" created INFO Kubernetes file "sidekiq-deployment.yaml" created

      These include yaml files with specs for the Rails application Service, Deployment, and ConfigMap, as well as for the db-data PersistentVolumeClaim and PostgreSQL database Deployment. Also included are files for Redis and Sidekiq respectively.

      To keep these manifests out of the main directory for your Rails project, create a new directory called k8s-manifests and then use the mv command to move the generated files into it:

      • mkdir k8s-manifests
      • mv *.yaml k8s-manifests

      Finally, cd into the k8s-manifests directory. We’ll work from inside this directory from now on to keep things tidy:

      These files are a good starting point, but in order for our application’s functionality to match the setup described in Containerizing a Ruby on Rails Application for Development with Docker Compose we will need to make a few additions and changes to the files that kompose has generated.

      Step 4 — Creating Kubernetes Secrets

      In order for our application to function in the way we expect, we will need to make a few modifications to the files that kompose has created. The first of these changes will be generating a Secret for our database user and password and adding it to our application and database Deployments. Kubernetes offers two ways of working with environment variables: ConfigMaps and Secrets. kompose has already created a ConfigMap with the non-confidential information we included in our .env file, so we will now create a Secret with our confidential information: our database name, username and password.

      The first step in manually creating a Secret will be to convert the data to base64, an encoding scheme that allows you to uniformly transmit data, including binary data.

      First convert the database name to base64 encoded data:

      • echo -n 'your_database_name' | base64

      Note down the encoded value.

      Next convert your database username:

      • echo -n 'your_database_username' | base64

      Again record the value you see in the output.

      Finally, convert your password:

      • echo -n 'your_database_password' | base64

      Take note of the value in the output here as well.

      Open a file for the Secret:

      Note: Kubernetes objects are typically defined using YAML, which strictly forbids tabs and requires two spaces for indentation. If you would like to check the formatting of any of your yaml files, you can use a linter or test the validity of your syntax using kubectl create with the --dry-run and --validate flags:

      • kubectl create -f your_yaml_file.yaml --dry-run --validate=true

      In general, it is a good idea to validate your syntax before creating resources with kubectl.

      Add the following code to the file to create a Secret that will define your DATABASE_NAME, DATABASE_USER and DATABASE_PASSWORD using the encoded values you just created. Be sure to replace the highlighted placeholder values here with your encoded database name, username and password:

      ~/rails_project/k8s-manifests/secret.yaml

      apiVersion: v1
      kind: Secret
      metadata:
        name: database-secret
      data:
        DATABASE_NAME: your_database_name
        DATABASE_PASSWORD: your_encoded_password
        DATABASE_USER: your_encoded_username
      

      We have named the Secret object database-secret, but you are free to name it anything you would like.

      These secrets are used with the Rails application so that it can connect to PostgreSQL. However, the database itself needs to be initialized with these same values. So next, copy the three lines and paste them at the end of the file. Edit the last three lines and change the DATABASE prefix for each variable to POSTGRES. Finally change the POSTGRES_NAME variable to read POSTGRES_DB.

      Your final secret.yaml file should contain the following:

      ~/rails_project/k8s-manifests/secret.yaml

      apiVersion: v1
      kind: Secret
      metadata:
        name: database-secret
      data:
        DATABASE_NAME: your_database_name
        DATABASE_PASSWORD: your_encoded_password
        DATABASE_USER: your_encoded_username
        POSTGRES_DB: your_database_name
        POSTGRES_PASSWORD: your_encoded_password
        POSTGRES_USER: your_encoded_username
      

      Save and close this file when you are finished editing. As you did with your .env file, be sure to add secret.yaml to your .gitignore file to keep it out of version control.

      With secret.yaml written, our next step will be to ensure that our application and database Deployments both use the values that we added to the file. Let’s start by adding references to the Secret to our application Deployment.

      Open the file called app-deployment.yaml:

      The file’s container specifications include the following environment variables defined under the env key:

      ~/rails_project/k8s-manifests/app-deployment.yaml

      apiVersion: apps/v1
      kind: Deployment
      . . .
          spec:
            containers:
              - env:
                  - name: DATABASE_HOST
                    valueFrom:
                      configMapKeyRef:
                        key: DATABASE_HOST
                        name: env
                  - name: DATABASE_PORT
                    valueFrom:
                      configMapKeyRef:
                        key: DATABASE_PORT
                        name: env
                  - name: RAILS_ENV
                    value: development
                  - name: REDIS_HOST
                    valueFrom:
                      configMapKeyRef:
                        key: REDIS_HOST
                        name: env
                  - name: REDIS_PORT
                    valueFrom:
                      configMapKeyRef:
                        key: REDIS_PORT
                        name: env
      . . .
      

      We will need to add references to our Secret so that our application will have access to those values. Instead of including a configMapKeyRef key to point to our env ConfigMap, as is the case with the existing values, we’ll include a secretKeyRef key to point to the values in our database-secret secret.

      Add the following Secret references after the - name: REDIS_PORT variable section:

      ~/rails_project/k8s-manifests/app-deployment.yaml

      . . .
          spec:
            containers:
              - env:
              . . .  
                  - name: REDIS_PORT
                    valueFrom:
                      configMapKeyRef:
                        key: REDIS_PORT
                        name: env
                  - name: DATABASE_NAME
                    valueFrom:
                      secretKeyRef:
                        name: database-secret
                        key: DATABASE_NAME
                  - name: DATABASE_PASSWORD
                    valueFrom:
                      secretKeyRef:
                        name: database-secret
                        key: DATABASE_PASSWORD
                  - name: DATABASE_USER
                    valueFrom:
                      secretKeyRef:
                        name: database-secret
                        key: DATABASE_USER
      . . .
      
      

      Save and close the file when you are finished editing. As with your secrets.yaml file, be sure to validate your edits using kubectl to ensure there are no issues with spaces, tabs, and indentation:

      • kubectl create -f app-deployment.yaml --dry-run --validate=true

      Output

      deployment.apps/app created (dry run)

      Next, we’ll add the same values to the database-deployment.yaml file.

      Open the file for editing:

      • nano database-deployment.yaml

      In this file, we will add references to our Secret for following variable keys: POSTGRES_DB, POSTGRES_USER and POSTGRES_PASSWORD. The postgres image makes these variables available so that you can modify the initialization of your database instance. The POSTGRES_DB creates a default database that is available when the container starts. The POSTGRES_USER and POSTGRES_PASSWORD together create a privileged user that can access the created database.

      Using the these values means that the user we create has access to all of the administrative and operational privileges of that role in PostgreSQL. When working in production, you will want to create a dedicated application user with appropriately scoped privileges.

      Under the POSTGRES_DB, POSTGRES_USER and POSTGRES_PASSWORD variables, add references to the Secret values:

      ~/rails_project/k8s-manifests/database-deployment.yaml

      apiVersion: apps/v1
      kind: Deployment
      . . .
          spec:
            containers:
              - env:
                  - name: PGDATA
                    value: /var/lib/postgresql/data/pgdata
                  - name: POSTGRES_DB
                    valueFrom:
                      secretKeyRef:
                        name: database-secret
                        key: POSTGRES_DB
                  - name: POSTGRES_PASSWORD
                    valueFrom:
                      secretKeyRef:
                        name: database-secret
                        key: POSTGRES_PASSWORD        
                  - name: POSTGRES_USER
                    valueFrom:
                      secretKeyRef:
                        name: database-secret
                        key: POSTGRES_USER
      . . .
      

      Save and close the file when you are finished editing. Again be sure to lint your edited file using kubectl with the --dry-run --validate=true arguments.

      With your Secret in place, you can move on to creating the database Service and ensuring that your application container only attempts to connect to the database once it is fully set up and initialized.

      Step 5 — Modifying the PersistentVolumeClaim and Exposing the Application Frontend

      Before running our application, we will make two final changes to ensure that our database storage will be provisioned properly and that we can expose our application frontend using a LoadBalancer.

      First, let’s modify the storage resource defined in the PersistentVolumeClaim that kompose created for us. This Claim allows us to dynamically provision storage to manage our application’s state.

      To work with PersistentVolumeClaims, you must have a StorageClass created and configured to provision storage resources. In our case, because we are working with DigitalOcean Kubernetes, our default StorageClass provisioner is set to dobs.csi.digitalocean.com — DigitalOcean Block Storage.

      We can check this by typing:

      If you are working with a DigitalOcean cluster, you will see the following output:

      Output

      NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE do-block-storage (default) dobs.csi.digitalocean.com Delete Immediate true 76m

      If you are not working with a DigitalOcean cluster, you will need to create a StorageClass and configure a provisioner of your choice. For details about how to do this, please see the official documentation.

      When kompose created db-data-persistentvolumeclaim.yaml, it set the storage resource to a size that does not meet the minimum size requirements of our provisioner. We will therefore need to modify our PersistentVolumeClaim to use the minimum viable DigitalOcean Block Storage unit: 1GB. Please feel free to modify this to meet your storage requirements.

      Open db-data-persistentvolumeclaim.yaml:

      • nano db-data-persistentvolumeclaim.yaml

      Replace the storage value with 1Gi:

      ~/rails_project/k8s-manifests/db-data-persistentvolumeclaim.yaml

      apiVersion: v1
      kind: PersistentVolumeClaim
      metadata:
        creationTimestamp: null
        labels:
          io.kompose.service: db-data
        name: db-data
      spec:
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi
      status: {}
      

      Also note the accessMode: ReadWriteOnce means that the volume provisioned as a result of this Claim will be read-write only by a single node. Please see the documentation for more information about different access modes.

      Save and close the file when you are finished.

      Next, open app-service.yaml:

      We are going to expose this Service externally using a DigitalOcean Load Balancer. If you are not using a DigitalOcean cluster, please consult the relevant documentation from your cloud provider for information about their load balancers. Alternatively, you can follow the official Kubernetes documentation on setting up a highly available cluster with kubeadm, but in this case you will not be able to use PersistentVolumeClaims to provision storage.

      Within the Service spec, specify LoadBalancer as the Service type:

      ~/rails_project/k8s-manifests/app-service.yaml

      apiVersion: v1
      kind: Service
      . . .
      spec:
        type: LoadBalancer
        ports:
      . . .
      

      When we create the app Service, a load balancer will be automatically created, providing us with an external IP where we can access our application.

      Save and close the file when you are finished editing.

      With all of our files in place, we are ready to start and test the application.

      Note:
      If you would like to compare your edited Kubernetes manifests to a set of reference files to be certain that your changes match this tutorial, the companion Github repository contains a set of tested manifests. You can compare each file individually, or you can also switch your local git branch to use the kubernetes-workflow branch.

      If you opt to switch branches, be sure to copy your secrets.yaml file into the new checked out version since we added it to .gitignore earlier in the tutorial.

      Step 6 — Starting and Accessing the Application

      It’s time to create our Kubernetes objects and test that our application is working as expected.

      To create the objects we’ve defined, we’ll use kubectl create with the -f flag, which will allow us to specify the files that kompose created for us, along with the files we wrote. Run the following command to create the Rails application and PostgreSQL database, Redis cache, and Sidekiq Services and Deployments, along with your Secret, ConfigMap, and PersistentVolumeClaim:

      • kubectl create -f app-deployment.yaml,app-service.yaml,database-deployment.yaml,database-service.yaml,db-data-persistentvolumeclaim.yaml,env-configmap.yaml,redis-deployment.yaml,redis-service.yaml,secret.yaml,sidekiq-deployment.yaml

      You receive the following output, indicating that the objects have been created:

      Output

      deployment.apps/app created service/app created deployment.apps/database created service/database created persistentvolumeclaim/db-data created configmap/env created deployment.apps/redis created service/redis created secret/database-secret created deployment.apps/sidekiq created

      To check that your Pods are running, type:

      You don’t need to specify a Namespace here, since we have created our objects in the default Namespace. If you are working with multiple Namespaces, be sure to include the -n flag when running this kubectl create command, along with the name of your Namespace.

      You will see output similar to the following while your database container is starting (the status will be either Pending or ContainerCreating):

      Output

      NAME READY STATUS RESTARTS AGE app-854d645fb9-9hv7w 1/1 Running 0 23s database-c77d55fbb-bmfm8 0/1 Pending 0 23s redis-7d65467b4d-9hcxk 1/1 Running 0 23s sidekiq-867f6c9c57-mcwks 1/1 Running 0 23s

      Once the database container is started, you will have output like this:

      Output

      NAME READY STATUS RESTARTS AGE app-854d645fb9-9hv7w 1/1 Running 0 30s database-c77d55fbb-bmfm8 1/1 Running 0 30s redis-7d65467b4d-9hcxk 1/1 Running 0 30s sidekiq-867f6c9c57-mcwks 1/1 Running 0 30s

      The Running STATUS indicates that your Pods are bound to nodes and that the containers associated with those Pods are running. READY indicates how many containers in a Pod are running. For more information, please consult the documentation on Pod lifecycles.

      Note:
      If you see unexpected phases in the STATUS column, remember that you can troubleshoot your Pods with the following commands:

      • kubectl describe pods your_pod
      • kubectl logs your_pod

      Now that your application is up and running, the last step that is required is to run Rails’ database migrations. This step will load a schema into the PostgreSQL database for the demo application.

      To run pending migrations you’ll exec into the running application pod and then call the rake db:migrate command.

      First, find the name of the application pod with the following command:

      Find the pod that corresponds to your application like the highlighted pod name in the following output:

      Output

      NAME READY STATUS RESTARTS AGE app-854d645fb9-9hv7w 1/1 Running 0 30s database-c77d55fbb-bmfm8 1/1 Running 0 30s redis-7d65467b4d-9hcxk 1/1 Running 0 30s sidekiq-867f6c9c57-mcwks 1/1 Running 0 30s

      With that pod name noted down, you can now run the kubectl exec command to complete the database migration step.

      Run the migrations with this command:

      • kubectl exec your_app_pod_name -- rake db:migrate

      You should receive output similar to the following, which indicates that the database schema has been loaded:

      Output

      == 20190927142853 CreateSharks: migrating ===================================== -- create_table(:sharks) -> 0.0190s == 20190927142853 CreateSharks: migrated (0.0208s) ============================ == 20190927143639 CreatePosts: migrating ====================================== -- create_table(:posts) -> 0.0398s == 20190927143639 CreatePosts: migrated (0.0421s) ============================= == 20191120132043 CreateEndangereds: migrating ================================ -- create_table(:endangereds) -> 0.8359s == 20191120132043 CreateEndangereds: migrated (0.8367s) =======================

      With your containers running and data loaded, you can now access the application. To get the IP for the app LoadBalancer, type:

      You will receive output like the following:

      Output

      NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE app LoadBalancer 10.245.73.142 your_lb_ip 3000:31186/TCP 21m database ClusterIP 10.245.155.87 <none> 5432/TCP 21m kubernetes ClusterIP 10.245.0.1 <none> 443/TCP 21m redis ClusterIP 10.245.119.67 <none> 6379/TCP 21m

      The EXTERNAL_IP associated with the app service is the IP address where you can access the application. If you see a <pending> status in the EXTERNAL_IP column, this means that your load balancer is still being created.

      Once you see an IP in that column, navigate to it in your browser: http://your_lb_ip:3000.

      You should see the following landing page:

      Application Landing Page

      Click on the Get Shark Info button. You will have a page with a button to create a new shark:

      Shark Info Form

      Click it and when prompted, enter the username and password from earlier in the tutorial series. If you did not change these values then the defaults are sammy and shark respectively.

      In the form, add a shark of your choosing. To demonstrate, we will add Megalodon Shark to the Shark Name field, and Ancient to the Shark Character field:

      Filled Shark Form

      Click on the Submit button. You will see a page with this shark information displayed back to you:

      Shark Output

      You now have a single instance setup of a Rails application with a PostgreSQL database running on a Kubernetes cluster. You also have a Redis cache and a Sidekiq worker to process data that users submit.

      Conclusion

      The files you have created in this tutorial are a good starting point to build from as you move toward production. As you develop your application, you can work on implementing the following:



      Source link

      Rails on Containers eBook


      Download the Complete eBook!

      Rails on Containers eBook in EPUB format

      Rails on Containers eBook in PDF format

      Introduction to the eBook

      This book is designed to introduce you to using containers and Kubernetes for full-stack development. You’ll learn how to develop a full-stack application using Ruby on Rails and PostgreSQL with Sidekiq, and how to manage them all — first with Docker, then with Docker Compose, and finally with Kubernetes.

      This book is based on the Rails on Containers tutorial series found on DigitalOcean Community. The topics that it covers include how to:

      1. Get started developing an application about sharks using the Ruby on Rails framework

      2. Extend the application’s data model to incorporate user submitted information about sharks

      3. Add the Stimulus JavaScript and Bootstrap CSS frameworks to your application to create visually appealing, interactive pages

      4. Integrate Sidekiq into your application to handle asynchronous data processing

      5. Containerize your application and streamline your development workflow using Docker Compose

      6. Migrate your Docker Compose development workflow to Kubernetes, finishing with a completely cloud-native application

      Each chapter is is designed to build progressively from the first. However, if you’re familiar with a topic, or are more interested in a particular section, feel free to jump to the chapter that best suits your purpose.

      Download the eBook

      You can download the eBook in either the EPUB or PDF format by following the links below.

      Download the Complete eBook!

      Rails on Containers eBook in EPUB format

      Rails on Containers eBook in PDF format

      If you’d like to learn more about app development using Rails visit the DigitalOcean Community’s Ruby on Rails section. Or if you want to continue learning about containers, Docker, and Kubernetes, you might be interested in the Kubernetes for Full-Stack Developers self-guided course.



      Source link

      Build a RESTful JSON API With Rails 5 – Part One


      Rails is popularly known for building web applications. Chances are if you’re reading this you’ve built a traditional server-rendered web application with Rails before. If not, I’d highly recommend going through the Getting Started with Rails page to familiarize yourself with the Rails framework before proceeding with this tutorial.

      As of version 5, Rails core now supports API only applications! In previous versions, we relied on an external gem: rails-api which has since been merged to core rails.

      API only applications are slimmed down compared to traditional Rails web applications. According to Rails 5 release notes, generating an API only application will:

      • Start the application with a limited set of middleware
      • Make the ApplicationController inherit from ActionController::API instead of ActionController::Base
      • Skip generation of view files

      This works to generate an API-centric framework excluding functionality that would otherwise be unused and unnecessary.

      In this three-part tutorial, we’ll build a todo list API where users can manage their to-do lists and todo items.

      Prerequisites

      Before we begin, make sure you have ruby version >=2.2.2 and rails version 5.

      $ ruby -v # ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin16]
      $ rails -v # Rails 5.0.1
      

      If your ruby version is not up to date, you can update it with a ruby version manager like rvm or rbenv.

      # when using rbenv
      $ rbenv install 2.3.1
      # set 2.3.1 as the global version
      $ rbenv global 2.3.1
      
      # when using rvm
      $ rvm install 2.3.1
      # set 2.3.1 as the global version
      $ rvm use 2.3.1
      

      If your rails version is not up to date, update to the latest version by running:

      $ gem update rails
      

      All good? Let’s get started!

      API Endpoints

      Our API will expose the following RESTful endpoints.

      Endpoint Functionality
      POST /signup Signup
      POST /auth/login Login
      GET /auth/logout Logout
      GET /todos List all todos
      POST /todos Create a new todo
      GET /todos/:id Get a todo
      PUT /todos/:id Update a todo
      DELETE /todos/:id Delete a todo and its items
      GET /todos/:id/items Get a todo item
      PUT /todos/:id/items Update a todo item
      DELETE /todos/:id/items Delete a todo item

      Part One will Cover:

      • Project setup
      • Todos API
      • TodoItems API

      Project Setup

      Generate a new project todos-api by running:

      $ rails new todos-api --api -T
      

      Note that we’re using the --api argument to tell Rails that we want an API application and -T to exclude Minitest the default
      testing framework. Don’t freak out, we’re going to write tests. We’ll be using RSpec instead to test our API. I find RSpec to be more expressive
      and easier to start with as compared to Minitest.

      Dependencies

      Let’s take a moment to review the gems that we’ll be using.

      • rspec-rails – Testing framework.
      • factorybotrails – A fixtures replacement with a more straightforward syntax. You’ll see.
      • shoulda_matchers – Provides RSpec with additional matchers.
      • database_cleaner – You guessed it! It literally cleans our test database to ensure
        a clean state in each test suite.
      • faker – A library for generating fake data. We’ll use this to generate test data.

      All good? Great! Let’s set them up. In your Gemfile:

      Add rspec-rails to both the :development and :test groups.

      # Gemfile
      group :development, :test do
        gem 'rspec-rails', '~> 3.5'
      end
      

      This is a handy shorthand to include a gem in multiple environments.

      Add factory_bot_rails, shoulda_matchers, faker and database_cleaner to the :test group.

      # Gemfile
      group :test do
        gem 'factory_bot_rails', '~> 4.0'
        gem 'shoulda-matchers', '~> 3.1'
        gem 'faker'
        gem 'database_cleaner'
      end
      

      Install the gems by running:

      $ bundle install
      

      Initialize the spec directory (where our tests will reside).

      $ rails generate rspec:install
      

      This adds the following files which are used for configuration:

      • .rspec
      • spec/spec_helper.rb
      • spec/rails_helper.rb

      Create a factories directory (factory bot uses this as the default directory). This is where we’ll define the model factories.

      $ mkdir spec/factories
      

      Configuration

      In spec/rails_helper.rb

      # require database cleaner at the top level
      require 'database_cleaner'
      
      # [...]
      # configure shoulda matchers to use rspec as the test framework and full matcher libraries for rails
      Shoulda::Matchers.configure do |config|
        config.integrate do |with|
          with.test_framework :rspec
          with.library :rails
        end
      end
      
      # [...]
      RSpec.configure do |config|
        # [...]
        # add `FactoryBot` methods
        config.include FactoryBot::Syntax::Methods
      
        # start by truncating all the tables but then use the faster transaction strategy the rest of the time.
        config.before(:suite) do
          DatabaseCleaner.clean_with(:truncation)
          DatabaseCleaner.strategy = :transaction
        end
      
        # start the transaction strategy as examples are run
        config.around(:each) do |example|
          DatabaseCleaner.cleaning do
            example.run
          end
        end
        # [...]
      end
      

      Phew! That was a rather long. Good thing is, it’s a smooth ride from here on out.


      Models

      Let’s start by generating the Todo model

      $ rails g model Todo title:string created_by:string
      

      Notice that we’ve included the model attributes in the model generation command. This way we don’t have to edit the migration file.
      The generator invokes active record and rspec to generate the migration, model, and spec respectively.

      # db/migrate/[timestamp]_create_todos.rb
      class CreateTodos < ActiveRecord::Migration[5.0]
        def change
          create_table :todos do |t|
            t.string :title
            t.string :created_by
      
            t.timestamps
          end
        end
      end
      

      And now the Item model

      $ rails g model Item name:string done:boolean todo:references
      

      By adding todo:references we’re telling the generator to set up an association with the Todo model.
      This will do the following:

      • Add a foreign key column todo_id to the items table
      • Setup a belongs_to association in the Item model
      # db/migrate/[timestamp]_create_items.rb
      class CreateItems < ActiveRecord::Migration[5.0]
        def change
          create_table :items do |t|
            t.string :name
            t.boolean :done
            t.references :todo, foreign_key: true
      
            t.timestamps
          end
        end
      end
      

      Looks good? Let’s run the migrations.

      $ rails db:migrate
      

      We’re Test Driven, let’s write the model specs first.

      # spec/models/todo_spec.rb
      require 'rails_helper'
      
      # Test suite for the Todo model
      RSpec.describe Todo, type: :model do
        # Association test
        # ensure Todo model has a 1:m relationship with the Item model
        it { should have_many(:items).dependent(:destroy) }
        # Validation tests
        # ensure columns title and created_by are present before saving
        it { should validate_presence_of(:title) }
        it { should validate_presence_of(:created_by) }
      end
      

      RSpec has a very expressive DSL (Domain Specific Language). You can almost read the tests like a paragraph.
      Remember our shoulda matchers gem? It provides RSpec with the nifty association and validation matchers above.

      # spec/models/item_spec.rb
      require 'rails_helper'
      
      # Test suite for the Item model
      RSpec.describe Item, type: :model do
        # Association test
        # ensure an item record belongs to a single todo record
        it { should belong_to(:todo) }
        # Validation test
        # ensure column name is present before saving
        it { should validate_presence_of(:name) }
      end
      

      Let’s execute the specs by running:

      $ bundle exec rspec
      

      And to no surprise, we have only one test passing and four failures. Let’s go ahead and fix the failures.

      # app/models/todo.rb
      class Todo < ApplicationRecord
        # model association
        has_many :items, dependent: :destroy
      
        # validations
        validates_presence_of :title, :created_by
      end
      
      # app/models/item.rb
      class Item < ApplicationRecord
        # model association
        belongs_to :todo
      
        # validation
        validates_presence_of :name
      end
      

      At this point run the tests again and…

      voila! All green.


      Controllers

      Now that our models are all setup, let’s generate the controllers.

      $ rails g controller Todos
      $ rails g controller Items
      

      You guessed it! Tests first… with a slight twist. Generating controllers by default generates controller specs.
      However, we won’t be writing any controller specs. We’re going to write request specs instead.

      Request specs are designed to drive behavior through the full stack, including routing. This means they can hit the applications’
      HTTP endpoints as opposed to controller specs which call methods directly. Since we’re building an API application, this is exactly the kind of behavior we want from our tests.

      According to RSpec, the official recommendation of the Rails team and the RSpec core team is to write request specs instead.

      Add a requests folder to the spec directory with the corresponding spec files.

      $ mkdir spec/requests && touch spec/requests/{todos_spec.rb,items_spec.rb} 
      

      Before we define the request specs, Let’s add the model factories which will provide the test data.

      Add the factory files:

      $ touch spec/factories/{todos.rb,items.rb}
      

      Define the factories.

      # spec/factories/todos.rb
      FactoryBot.define do
        factory :todo do
          title { Faker::Lorem.word }
          created_by { Faker::Number.number(10) }
        end
      end
      

      By wrapping faker methods in a block, we ensure that faker generates dynamic data every time the factory is invoked.
      This way, we always have unique data.

      # spec/factories/items.rb
      FactoryBot.define do
        factory :item do
          name { Faker::StarWars.character }
          done false
          todo_id nil
        end
      end
      

      Todo API

      # spec/requests/todos_spec.rb
      require 'rails_helper'
      
      RSpec.describe 'Todos API', type: :request do
        # initialize test data 
        let!(:todos) { create_list(:todo, 10) }
        let(:todo_id) { todos.first.id }
      
        # Test suite for GET /todos
        describe 'GET /todos' do
          # make HTTP get request before each example
          before { get '/todos' }
      
          it 'returns todos' do
            # Note `json` is a custom helper to parse JSON responses
            expect(json).not_to be_empty
            expect(json.size).to eq(10)
          end
      
          it 'returns status code 200' do
            expect(response).to have_http_status(200)
          end
        end
      
        # Test suite for GET /todos/:id
        describe 'GET /todos/:id' do
          before { get "/todos/#{todo_id}" }
      
          context 'when the record exists' do
            it 'returns the todo' do
              expect(json).not_to be_empty
              expect(json['id']).to eq(todo_id)
            end
      
            it 'returns status code 200' do
              expect(response).to have_http_status(200)
            end
          end
      
          context 'when the record does not exist' do
            let(:todo_id) { 100 }
      
            it 'returns status code 404' do
              expect(response).to have_http_status(404)
            end
      
            it 'returns a not found message' do
              expect(response.body).to match(/Couldn't find Todo/)
            end
          end
        end
      
        # Test suite for POST /todos
        describe 'POST /todos' do
          # valid payload
          let(:valid_attributes) { { title: 'Learn Elm', created_by: '1' } }
      
          context 'when the request is valid' do
            before { post '/todos', params: valid_attributes }
      
            it 'creates a todo' do
              expect(json['title']).to eq('Learn Elm')
            end
      
            it 'returns status code 201' do
              expect(response).to have_http_status(201)
            end
          end
      
          context 'when the request is invalid' do
            before { post '/todos', params: { title: 'Foobar' } }
      
            it 'returns status code 422' do
              expect(response).to have_http_status(422)
            end
      
            it 'returns a validation failure message' do
              expect(response.body)
                .to match(/Validation failed: Created by can't be blank/)
            end
          end
        end
      
        # Test suite for PUT /todos/:id
        describe 'PUT /todos/:id' do
          let(:valid_attributes) { { title: 'Shopping' } }
      
          context 'when the record exists' do
            before { put "/todos/#{todo_id}", params: valid_attributes }
      
            it 'updates the record' do
              expect(response.body).to be_empty
            end
      
            it 'returns status code 204' do
              expect(response).to have_http_status(204)
            end
          end
        end
      
        # Test suite for DELETE /todos/:id
        describe 'DELETE /todos/:id' do
          before { delete "/todos/#{todo_id}" }
      
          it 'returns status code 204' do
            expect(response).to have_http_status(204)
          end
        end
      end
      

      We start by populating the database with a list of 10 todo records (thanks to factory bot).
      We also have a custom helper method json which parses the JSON response to a Ruby Hash which is easier to work with in our tests.
      Let’s define it in spec/support/request_spec_helper.

      Add the directory and file:

      $ mkdir spec/support && touch spec/support/request_spec_helper.rb
      
      # spec/support/request_spec_helper
      module RequestSpecHelper
        # Parse JSON response to ruby hash
        def json
          JSON.parse(response.body)
        end
      end
      

      The support directory is not autoloaded by default. To enable this, open the rails helper and comment out the support directory auto-loading and then
      include it as shared module for all request specs in the RSpec configuration block.

      # spec/rails_helper.rb
      # [...]
      Dir[Rails.root.join('spec/support/**/*.rb')].each { |f| require f }
      # [...]
      RSpec.configuration do |config|
        # [...]
        config.include RequestSpecHelper, type: :request
        # [...]
      end
      

      Run the tests.

      We get failing routing errors. This is because we haven’t defined the routes yet. Go ahead and define them in config/routes.rb.

      # config/routes.rb
      Rails.application.routes.draw do
        resources :todos do
          resources :items
        end
      end
      

      In our route definition, we’re creating todo resource with a nested items resource. This enforces the 1:m (one to many) associations at the routing level.
      To view the routes, you can run:

      $ rails routes
      

      When we run the tests we see that the routing error is gone. As expected we have controller failures. Let’s go ahead and define the controller methods.

      # app/controllers/todos_controller.rb
      class TodosController < ApplicationController
        before_action :set_todo, only: [:show, :update, :destroy]
      
        # GET /todos
        def index
          @todos = Todo.all
          json_response(@todos)
        end
      
        # POST /todos
        def create
          @todo = Todo.create!(todo_params)
          json_response(@todo, :created)
        end
      
        # GET /todos/:id
        def show
          json_response(@todo)
        end
      
        # PUT /todos/:id
        def update
          @todo.update(todo_params)
          head :no_content
        end
      
        # DELETE /todos/:id
        def destroy
          @todo.destroy
          head :no_content
        end
      
        private
      
        def todo_params
          # whitelist params
          params.permit(:title, :created_by)
        end
      
        def set_todo
          @todo = Todo.find(params[:id])
        end
      end
      

      More helpers. Yay! This time we have:

      • json_response which does… yes, responds with JSON and an HTTP status code (200 by default).
        We can define this method in concerns folder.
      # app/controllers/concerns/response.rb
      module Response
        def json_response(object, status = :ok)
          render json: object, status: status
        end
      end
      
      • set_todo – callback method to find a todo by id. In the case where the record does not exist, ActiveRecord
        will throw an exception ActiveRecord::RecordNotFound. We’ll rescue from this exception and return a 404 message.
      # app/controllers/concerns/exception_handler.rb
      module ExceptionHandler
        # provides the more graceful `included` method
        extend ActiveSupport::Concern
      
        included do
          rescue_from ActiveRecord::RecordNotFound do |e|
            json_response({ message: e.message }, :not_found)
          end
      
          rescue_from ActiveRecord::RecordInvalid do |e|
            json_response({ message: e.message }, :unprocessable_entity)
          end
        end
      end
      

      In our create method in the TodosController, note that we’re using create! instead of create. This way, the model will raise
      an exception ActiveRecord::RecordInvalid. This way, we can avoid deep nested if statements in the controller. Thus, we rescue from this exception
      in the ExceptionHandler module.

      However, our controller classes don’t know about these helpers yet. Let’s fix that by including these modules in the
      application controller.

      # app/controllers/application_controller.rb
      class ApplicationController < ActionController::API
        include Response
        include ExceptionHandler
      end
      

      Run the tests and everything’s all green!

      Let’s fire up the server for some good old manual testing.

      $ rails s
      

      Now let’s go ahead and make requests to the API. I’ll be using httpie as my HTTP client.

      # GET /todos
      $ http :3000/todos
      # POST /todos
      $ http POST :3000/todos title=Mozart created_by=1
      # PUT /todos/:id
      $ http PUT :3000/todos/1 title=Beethoven
      # DELETE /todos/:id
      $ http DELETE :3000/todos/1
      

      You should see similar output.


      TodoItems API

      # spec/requests/items_spec.rb
      require 'rails_helper'
      
      RSpec.describe 'Items API' do
        # Initialize the test data
        let!(:todo) { create(:todo) }
        let!(:items) { create_list(:item, 20, todo_id: todo.id) }
        let(:todo_id) { todo.id }
        let(:id) { items.first.id }
      
        # Test suite for GET /todos/:todo_id/items
        describe 'GET /todos/:todo_id/items' do
          before { get "/todos/#{todo_id}/items" }
      
          context 'when todo exists' do
            it 'returns status code 200' do
              expect(response).to have_http_status(200)
            end
      
            it 'returns all todo items' do
              expect(json.size).to eq(20)
            end
          end
      
          context 'when todo does not exist' do
            let(:todo_id) { 0 }
      
            it 'returns status code 404' do
              expect(response).to have_http_status(404)
            end
      
            it 'returns a not found message' do
              expect(response.body).to match(/Couldn't find Todo/)
            end
          end
        end
      
        # Test suite for GET /todos/:todo_id/items/:id
        describe 'GET /todos/:todo_id/items/:id' do
          before { get "/todos/#{todo_id}/items/#{id}" }
      
          context 'when todo item exists' do
            it 'returns status code 200' do
              expect(response).to have_http_status(200)
            end
      
            it 'returns the item' do
              expect(json['id']).to eq(id)
            end
          end
      
          context 'when todo item does not exist' do
            let(:id) { 0 }
      
            it 'returns status code 404' do
              expect(response).to have_http_status(404)
            end
      
            it 'returns a not found message' do
              expect(response.body).to match(/Couldn't find Item/)
            end
          end
        end
      
        # Test suite for PUT /todos/:todo_id/items
        describe 'POST /todos/:todo_id/items' do
          let(:valid_attributes) { { name: 'Visit Narnia', done: false } }
      
          context 'when request attributes are valid' do
            before { post "/todos/#{todo_id}/items", params: valid_attributes }
      
            it 'returns status code 201' do
              expect(response).to have_http_status(201)
            end
          end
      
          context 'when an invalid request' do
            before { post "/todos/#{todo_id}/items", params: {} }
      
            it 'returns status code 422' do
              expect(response).to have_http_status(422)
            end
      
            it 'returns a failure message' do
              expect(response.body).to match(/Validation failed: Name can't be blank/)
            end
          end
        end
      
        # Test suite for PUT /todos/:todo_id/items/:id
        describe 'PUT /todos/:todo_id/items/:id' do
          let(:valid_attributes) { { name: 'Mozart' } }
      
          before { put "/todos/#{todo_id}/items/#{id}", params: valid_attributes }
      
          context 'when item exists' do
            it 'returns status code 204' do
              expect(response).to have_http_status(204)
            end
      
            it 'updates the item' do
              updated_item = Item.find(id)
              expect(updated_item.name).to match(/Mozart/)
            end
          end
      
          context 'when the item does not exist' do
            let(:id) { 0 }
      
            it 'returns status code 404' do
              expect(response).to have_http_status(404)
            end
      
            it 'returns a not found message' do
              expect(response.body).to match(/Couldn't find Item/)
            end
          end
        end
      
        # Test suite for DELETE /todos/:id
        describe 'DELETE /todos/:id' do
          before { delete "/todos/#{todo_id}/items/#{id}" }
      
          it 'returns status code 204' do
            expect(response).to have_http_status(204)
          end
        end
      end
      

      As expected, running the tests at this point should output failing todo item tests. Let’s define the todo items controller.

      # app/controllers/items_controller.rb
      class ItemsController < ApplicationController
        before_action :set_todo
        before_action :set_todo_item, only: [:show, :update, :destroy]
      
        # GET /todos/:todo_id/items
        def index
          json_response(@todo.items)
        end
      
        # GET /todos/:todo_id/items/:id
        def show
          json_response(@item)
        end
      
        # POST /todos/:todo_id/items
        def create
          @todo.items.create!(item_params)
          json_response(@todo, :created)
        end
      
        # PUT /todos/:todo_id/items/:id
        def update
          @item.update(item_params)
          head :no_content
        end
      
        # DELETE /todos/:todo_id/items/:id
        def destroy
          @item.destroy
          head :no_content
        end
      
        private
      
        def item_params
          params.permit(:name, :done)
        end
      
        def set_todo
          @todo = Todo.find(params[:todo_id])
        end
      
        def set_todo_item
          @item = @todo.items.find_by!(id: params[:id]) if @todo
        end
      end
      

      Run the tests.

      Run some manual tests for the todo items API:

      # GET /todos/:todo_id/items
      $ http :3000/todos/2/items
      # POST /todos/:todo_id/items
      $ http POST :3000/todos/2/items name="Listen to 5th Symphony" done=false
      # PUT /todos/:todo_id/items/:id
      $ http PUT :3000/todos/2/items/1 done=true
      # DELETE /todos/:todo_id/items/1
      $ http DELETE :3000/todos/2/items/1
      


      Conclusion

      That’s it for part one! At this point you should have learned how to:

      • Generate an API application with Rails 5
      • Setup RSpec testing framework with Factory Bot, Database Cleaner, Shoulda Matchers and Faker.
      • Build models and controllers with TDD (Test Driven Development).
      • Make HTTP requests to an API with httpie.

      In the next part, we’ll cover authentication with JWT, pagination, and API versioning. Hope to see you there. Cheers!



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