PIMS-1328 Express Error Handling

[dbarkowsky]

🎯 Summary

PIMS-1328

Changes

• Added a fallback route handler that returns 404 if that route doesn't exist.
• Added some preset error responses we can use if wanted.
• Added error handler middleware to catch errors and send back a formatted response.
  • The next() function accepts string, Error, and ErrorWithCode.
• Added some process listeners that will close the app in a controlled manner, closing existing connections first.

Testing

• Easiest way to test is to add a temporary endpoint in express.ts (I used /error). This endpoint can then just throw different kinds of errors to see different responses.

app.use('/error', (req: Request, res: Response) => {
  throw new Error('hi')
})

• Recommended to use next() instead, as it also allows this to work with async controllers.

app.use('/error', async (req: Request, res: Response, next: NextFunction) => {
  next(new Error('hi'))
})

or even just

app.use('/error', async (req: Request, res: Response, next: NextFunction) => {
  next('hi')
})

• Test the SIGTERM one by using this somewhere

app.use('/error', async (req: Request, res: Response, next: NextFunction) => {
  process.kill(process.pid, 'SIGTERM')
})

• Test the non-existent route by calling a route that doesn't exist (e.g. /help)

🔰 Checklist

• I have read and agree with the following checklist and am following the guidelines in our Code of Conduct document.

• I have performed a self-review of my code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation where required.
• I have tested my changes to the best of my ability.
• My changes generate no new warnings.

[github-actions]

🚀 Deployment Information

The API Image has been built with the tag: 2197. Please make sure to utilize this specific tag when promoting these changes to the TEST and PROD environments during the API deployment. For more updates please monitor Image Tags Page on Wiki.

[codeclimate]

Code Climate has analyzed commit 323d045 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 91.1%.

View more on Code Climate.

[TaylorFries]

Bad endpoints caught and SIGTERM handled well. App never crashed!