NodeJS CI/CD Build Missing Files

Question

I am setting up CI/CD for a NodeJS project and occasionally the developer forgets to send up a file (module) to source control. I run npm ci and npm test without problem and the application gets deployed to my server. However, it will error out once executed due to the missing module.

Is there a best practice for ensuring that all files required by a node application are available before allowing it to be deployed?

Answer 1

I don't know your exact configuration but here is how my teams have handled similar issues in the past:

1. Unit Tests. Normally, a CI system can catch this type of error before you deploy. If your CI tests aren't flagging your missing module before the code gets deployed, then a commonly used solution would be to write a test that ensures the module is present. That way the problem would be automatically caught when your unit tests are run. Something along these lines might work:

// mymodule.test.js using Mocha syntax:
import {expect} from 'chai';
import mymodule from './mymodule';

describe('my module', () => {
  it('should export something!', () => {
    expect(!!mymodule).to.be.true;
  });
});

2. Version Control workflow. It sounds like there is also an issue here with your team's version control workflow. Generally, all of the files required to build the production application should be kept under version control and developers should be committing frequently. In this situation, I would normally do some investigation to see what is happening -- it might require training or perhaps the app is structured in a way that is overly confusing or complex to engineers.

3. Use a lockfile for npm packages. If the missing module is a npm modules, then there are a few things that could cause it to be missing. Generally, all npm modules should be listed in your package-lock.json or yarn.lock file. This ensures that the production version of the application will be in sync with what developers are using locally. I personally discourage developers from installing npm modules globally unless it is absolutely necessary. In that situation, your CI server (and perhaps your production server) will need to be updated to include the exact same versions of the global packages.

4. Automated build systems. I think you are indicating that your problem is caused by modules that aren't under source control. But I have also seen some situations where legacy build systems might omit a file that is important when building the app for production. Modern build tools like Webpack and Babel normally include every module referenced by the application but older solutions like grunt and gulp might require some fine-tuning to ensure the files are always included in an automated way (to avoid a situation where developers are expected to manually add the modules to the build system and often forget to do so).