Docker for Web Developers/

...

/

Live Editing and Debugging

Live Editing and Debugging

Learn how changes are reflected in a running app and how you can debug it.

We'll cover the following...

Live code editing

When the nodehello container is running in development mode, you can edit index.js, and Nodemon will restart the application when you save the file.

For example, examine line 17:

const message = `Hello ${ req.params.name  || 'World' }!`;

and change Hello to Hey there:

const message = `Hey there, ${ req.params.name  || 'World' }!`;

Practice

Click on the “Run” button and then click the URL on “Your app can found at:”; you will be able to see “Hey there, World!”

Now replace there on line 17 with your_name, click on the “Run” button, and refresh the browser.

mkdir nodejs
useradd -m node
chown -R node nodejs
clear
cp -r /usercode/docker-compose.yml /usercode/nodejs/
cp -r /usercode/package.json /usercode/nodejs/
cp -r /usercode/.dockerignore /usercode/nodejs/
cp -r /usercode/Dockerfile /usercode/nodejs/
cp -r /usercode/index.js /usercode/nodejs/
cd nodejs
clear
docker-compose up
Live code editing

Remote container debugging

This section describes how to debug a Node.js application running in a Docker Container. The information in the section can also be applied to other runtimes with similar facilities.

Node.js debugging overview

To debug a Node.js application, you can:

  1. Set the NODE_ENV environment variable to development. Many modules use this to show more verbose errors or record logs. It has been set in both Dockerfile and docker-compose.yml.

  2. Launch node with the --inspect=0.0.0.0:9229 parameter. This starts the debugger listening on port 9229 and allows connections from any device. The npm run debug command defined in package.json has this set. ...