Quick start with odo v3

This guide will run through creating a simple hello world devfile project using odo version 3. The purpose of this guide is to provide a practical introduction to those just starting out with devfiles.

Prerequisites

odo v3
Access to a Kubernetes or OpenShift cluster

Procedure

Access or setup your target cluster
- (Optional) You can use minikube to run your cluster locally, follow these steps to get started
Install odo version 3 if you do not already have it by following the Installation guide
Once installed, use odo login to login with your cluster credentials
- This step is not needed if using minikube

Create a directory to store a simple hello world Express.js application

package.json file

package.json

{
    "name": "helloworld-example",
    "version": "1.0.0",
    "description": "",
    "main": "app.js",
    "type": "module",
    "dependencies": {
        "@types/express": "^4.17.17",
        "express": "^4.18.2"
    },
    "scripts": {
        "start": "node app.js"
    }
}

Application source code

app.js

import express from "express"


const PORT = 3000
const app = express()


app.get("/", (req, res) => {
    res.send("Hello world!")
})


app.listen(PORT, () => {
    console.log(`Listening on port ${PORT}..`)
})

(Optional) Normally it is recommended to use odo init to start your project from a devfile registry stack, see Developing with Node.JS and Command Reference: odo init for details, steps 6-11 will go through the process of making the devfile from scratch
- For this project, run odo init --name helloworld-example --devfile nodejs, to test this devfile in action, skip to step 12
Create a devfile with the filename .devfile.yaml. Add the schemaVersion field with the desired devfile specification version to use
.devfile.yaml
```
schemaVersion: 2.0.0
```
Next, create the first component to serve as the runtime for the project, for this use the container component with the name runtime and the node:18-alpine image
- name is the identifier used to refer to the component
- image is the container image to use for the component
  .devfile.yaml
```
 schemaVersion: 2.0.0
+components:
+  - name: runtime
+    container:
+      image: node:18-alpine
```
The runtime container hosts the expressjs app created which listens on port 3000, define this port in the component by specifying an entry under endpoints
- Each endpoint has at least a name to identify them and the targetPort to specify the port number to forward
  .devfile.yaml
```
 schemaVersion: 2.0.0
 components:
   - name: runtime
     container:
       image: node:18-alpine
+      endpoints:
+        - name: http-3000
+          targetPort: 3000
```
Now that the runtime container is defined, commands are needed to tell odo what to do during the step of the development runtime (odo dev). Define the command to install the dependencies needed to run the application (npm install)
- The id field identifies the command by a label which can be used to specify which command to run by the dev tool
  - Example: odo dev --build-command install
- An exec command specifies explicit shell command(s) to run on a given component
- commandLine defines the shell command(s) to execute as part of that devfile command
- The group specifies what kind of command it is or if it is the default of its kind, isDefault
  - build commands runs before run commands
    .devfile.yaml
```
 schemaVersion: 2.0.0
 components:
   - name: runtime
     container:
       image: node:18-alpine
       endpoints:
         - name: http-3000
           targetPort: 3000
+commands:
+  - id: install
+    exec:
+      commandLine: npm install
+      component: runtime
+      workingDir: ${PROJECT_SOURCE}
+      group:
+        isDefault: true
+        kind: build
```

Next, define the command to run the application (node app.js)

.devfile.yaml

 schemaVersion: 2.0.0
 components:
   - name: runtime
     container:
       image: node:18-alpine
       endpoints:
         - name: http-3000
           targetPort: 3000
 commands:
   - id: install
     exec:
       commandLine: npm install
       component: runtime
       workingDir: ${PROJECT_SOURCE}
       group:
         isDefault: true
         kind: build
+  - id: run
+    exec:
+      commandLine: node app.js
+      component: runtime
+      workingDir: ${PROJECT_SOURCE}
+      group:
+        isDefault: true
+        kind: run

Now the devfile is ready to be used to run the application

Devfile for Hello World application

.devfile.yaml

schemaVersion: 2.0.0
components:
  - name: runtime
    container:
      image: node:18-alpine
      endpoints:
        - name: http-3000
          targetPort: 3000
commands:
  - id: install
    exec:
      commandLine: npm install
      component: runtime
      workingDir: ${PROJECT_SOURCE}
      group:
        isDefault: true
        kind: build
  - id: run
    exec:
      commandLine: node app.js
      component: runtime
      workingDir: ${PROJECT_SOURCE}
      group:
        isDefault: true
        kind: run

Run odo dev and you should see the following output

odo dev output

 __
/  \__     Developing using the "helloworld-devfile" Devfile
\__/  \    Namespace: default
/  \__/    odo version: v3.9.0
\__/


⚠  You are using "default" namespace, odo may not work as expected in the default namespace.
⚠  You may set a new namespace by running `odo create namespace <name>`, or set an existing one by running `odo set namespace <name>`


↪ Running on the cluster in Dev mode
•  Waiting for Kubernetes resources  ...
⚠  Pod is Pending
✓  Pod is Running
✓  Syncing files into the container [401ms]
✓  Building your application in container (command: install) [1s]
•  Executing the application (command: run)  ...
-  Forwarding from 127.0.0.1:20001 -> 3000




↪ Dev mode
Status:
Watching for changes in the current directory /path/to/project


Keyboard Commands:
[Ctrl+c] - Exit and delete resources from the cluster
    [p] - Manually apply local changes to the application on the cluster

The application port 3000 served in the cluster gets routed to your host on a different port (in this case 20001). Run curl http://localhost:20001 and you should see the following output
Response content returned by curl
```
Hello world!%
```
Congratulations! You have written your first devfile project with odo!

Devfile.io