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Creating a multicomponent application with odo

odo allows you to create a multicomponent application, modify it, and link its components in an easy and automated way.

This example describes how to deploy a multicomponent application - a shooter game. The application consists of a front-end Node.js component and a back-end Java component.

Prerequisites

  • odo is installed.

  • You have a running OpenShift Container Platform cluster. Developers can use CodeReady Containers (CRC) to deploy a local OpenShift Container Platform cluster quickly.

  • Maven is installed.

Creating a project

Create a project to keep your source code, tests, and libraries organized in a separate single unit.

Procedure

  1. Log in to an OpenShift Container Platform cluster:

    $ odo login -u developer -p developer

  2. Create a project:

    $ odo project create myproject
 ✓  Project 'myproject' is ready for use
 ✓  New project created and now using project : myproject

Deploying the back-end component

To create a Java component, import the Java builder image, download the Java application and push the source code to your cluster with odo.

Procedure

  1. Import openjdk18 into the cluster:

    $ oc import-image openjdk18 \
--from=registry.access.redhat.com/redhat-openjdk-18/openjdk18-openshift --confirm

  2. Tag the image as builder to make it accessible for odo:

    $ oc annotate istag/openjdk18:latest tags=builder

  3. Run odo catalog list components to see the created image:

    $ odo catalog list components
Odo Supported OpenShift Components:
NAME          PROJECT       TAGS
nodejs        openshift     10,8,8-RHOAR,latest
openjdk18     myproject     latest

  4. Create a directory for your components:

    $ mkdir my_components $$ cd my_components

  5. Download the example back-end application:

    $ git clone https://github.com/openshift-evangelists/Wild-West-Backend backend

  6. Change directory to the back-end source directory and check that you have the correct files in the directory:

    $ cd backend
$ ls
debug.sh  pom.xml  src

  7. Build the back-end source files with Maven to create a JAR file:

    $ mvn package
...
[INFO] --------------------------------------
[INFO] BUILD SUCCESS
[INFO] --------------------------------------
[INFO] Total time: 2.635 s
[INFO] Finished at: 2019-09-30T16:11:11-04:00
[INFO] Final Memory: 30M/91M
[INFO] --------------------------------------

  8. Create a component configuration of Java component-type named backend:

    $ odo create openjdk18 backend --binary target/wildwest-1.0.jar
 ✓  Validating component [1ms]
 Please use `odo push` command to create the component with source deployed

    Now the configuration file config.yaml is in the local directory of the back-end component that contains information about the component for deployment.

  9. Check the configuration settings of the back-end component in the config.yaml file using:

    $ odo config view
COMPONENT SETTINGS
------------------------------------------------
PARAMETER         CURRENT_VALUE
Type              openjdk18
Application       app
Project           myproject
SourceType        binary
Ref
SourceLocation    target/wildwest-1.0.jar
Ports             8080/TCP,8443/TCP,8778/TCP
Name              backend
MinMemory
MaxMemory
DebugPort
Ignore
MinCPU
MaxCPU

  10. Push the component to the OpenShift Container Platform cluster.

    $ odo push
Validation
 ✓  Checking component [6ms]

Configuration changes
 ✓  Initializing component
 ✓  Creating component [124ms]

Pushing to component backend of type binary
 ✓  Checking files for pushing [1ms]
 ✓  Waiting for component to start [48s]
 ✓  Syncing files to the component [811ms]
 ✓  Building component [3s]

    Using odo push, OpenShift Container Platform creates a container to host the back-end component, deploys the container into a Pod running on the OpenShift Container Platform cluster, and starts the backend component.

  11. Validate:

    • The status of the action in odo:

      odo log -f
2019-09-30 20:14:19.738  INFO 444 --- [           main] c.o.wildwest.WildWestApplication         : Starting WildWestApplication v1.0 onbackend-app-1-9tnhc with PID 444 (/deployments/wildwest-1.0.jar started by jboss in /deployments)

    • The status of the back-end component:

      $ odo list
APP     NAME        TYPE          SOURCE                             STATE
app     backend     openjdk18     file://target/wildwest-1.0.jar     Pushed

Deploying the front-end component

To create and deploy a front-end component, download the Node.js application and push the source code to your cluster with odo.

Procedure

  1. Download the example front-end application:

    $ git clone https://github.com/openshift/nodejs-ex

  2. Change the current directory to the front-end directory:

    $ cd <directory-name>

  3. List the contents of the directory to see that the front end is a Node.js application.

    $ ls
assets  bin  index.html  kwww-frontend.iml  package.json  package-lock.json  playfield.png  README.md  server.js

    The front-end component is written in an interpreted language (Node.js); it does not need to be built.

  4. Create a component configuration of Node.js component-type named frontend:

    $ odo create nodejs frontend
 ✓  Validating component [5ms]
Please use `odo push` command to create the component with source deployed

  5. Push the component to a running container.

    $ odo push
Validation
 ✓  Checking component [8ms]

Configuration changes
 ✓  Initializing component
 ✓  Creating component [83ms]

Pushing to component frontend of type local
 ✓  Checking files for pushing [2ms]
 ✓  Waiting for component to start [45s]
 ✓  Syncing files to the component [3s]
 ✓  Building component [18s]
 ✓  Changes successfully pushed to component

Linking both components

Components running on the cluster need to be connected in order to interact. OpenShift Container Platform provides linking mechanisms to publish communication bindings from a program to its clients.

Procedure

  1. List all the components that are running on the cluster:

    $ odo list
APP     NAME         TYPE          SOURCE                             STATE
app     backend      openjdk18     file://target/wildwest-1.0.jar     Pushed
app     frontend     nodejs        file://./                          Pushed

  2. Link the current front-end component to the backend:

    $ odo link backend --port 8080
 ✓  Component backend has been successfully linked from the component frontend

Following environment variables were added to frontend component:
- COMPONENT_BACKEND_HOST
- COMPONENT_BACKEND_PORT

    The configuration information of the back-end component is added to the front-end component and the front-end component restarts.

Exposing components to the public

Procedure

  1. Create an external URL for the application:

    $ cd frontend
$ odo url create frontend --port 8080
 ✓  URL frontend created for component: frontend

To create URL on the OpenShift  cluster, use `odo push`

  2. Apply the changes:

    $ odo push
Validation
 ✓  Checking component [21ms]

Configuration changes
 ✓  Retrieving component data [35ms]
 ✓  Applying configuration [29ms]

Applying URL changes
 ✓  URL frontend: http://frontend-app-myproject.192.168.42.79.nip.io created

Pushing to component frontend of type local
 ✓  Checking file changes for pushing [1ms]
 ✓  No file changes detected, skipping build. Use the '-f' flag to force the build.

  3. Open the URL in a browser to view the application.

If an application requires permissions to the active Service Account to access the OpenShift Container Platform namespace and delete active pods, the following error may occur when looking at odo log from the back-end component:

Message: Forbidden!Configured service account doesn’t have access. Service account may have been revoked

To resolve this error, add permissions for the Service Account role:

$ oc policy add-role-to-group view system:serviceaccounts -n <project>
$ oc policy add-role-to-group edit system:serviceaccounts -n <project>

Do not do this on a production cluster.

Modifying the running application

Procedure

  1. Change the local directory to the front-end directory:

    $ cd ~/frontend

  2. Monitor the changes on the file system using:

    $ odo watch

  3. Edit the index.html file to change the displayed name for the game.

    A slight delay is possible before odo recognizes the change.

    odo pushes the changes to the front-end component and prints its status to the terminal:

    File /root/frontend/index.html changed
File  changed
Pushing files...
 ✓  Waiting for component to start
 ✓  Copying files to component
 ✓  Building component

  4. Refresh the application page in the web browser. The new name is now displayed.

Deleting an application

Deleting an application will delete all components associated with the application.
Procedure

  1. List the applications in the current project:

    $ odo app list
    The project '<project_name>' has the following applications:
    NAME
    app

  2. List the components associated with the applications. These components will be deleted with the application:

    $ odo component list
    APP     NAME                      TYPE       SOURCE        STATE
    app     nodejs-nodejs-ex-elyf     nodejs     file://./     Pushed

  3. Delete the application:

    $ odo app delete <application_name>
    ? Are you sure you want to delete the application: <application_name> from project: <project_name>

  4. Confirm the deletion with Y. You can suppress the confirmation prompt using the -f flag.