Unable to grab references to uncaught exceptions

[ajjindal]

I work at Sentry, an open source software for application monitoring. We are adding support for Node+Cloud Functions to automatically report code errors. However, we are not able to get reference to the handler in order to capture uncaught exceptions. developers are required to manually catch the error and report it (https://github.com/GoogleCloudPlatform/stackdriver-errors-js#usage).

Here's current Sentry Node integration on Cloud Functions (https://docs.sentry.io/platforms/node/guides/gcp-functions/). This requires captureException call.

As a result of conversation with Steren and Vinod, posting the issue here.
cc: @steren @grant

[grant]

Hi @ajjindal, I'm not able to reproduce the issue.

Can you provide a clear, minimal setup for reproducing this issue?

For example, couldn't you just wrap your function in a try/catch? Are you saying the framework itself is throwing an exception that you want to catch?

---

For creating a global exception handler, I believe we could use Express middleware to register a global exception handler to all routes.

I have a blogpost with using middleware:
https://medium.com/google-cloud/express-routing-with-google-cloud-functions-36fb55885c68

Let me know how to help, or what you're looking for specifically.

[ajjindal]

To clarify, this is not a bug but more like an ask to support handling of uncaught exceptions through third party like Sentry.

I am looking for a pointer to the handler to be able to grab uncaught exceptions and report them into Sentry.
Steps to reproduce:

• Create a cloud function using Nodejs and make it throw an error
• Instrument Sentry (https://docs.sentry.io/platforms/node/guides/gcp-functions/) or any other error handling tool for that matter
• As you execute the function, the error won't be reported unless the exception is specifically reported from the catch block.

Gave more details to Steren and Vinod.

[grant]

OK, thanks for some more details. Would it be okay to catch uncaught exceptions with the Node process and handle them with Sentry?

process.on('uncaughtException', function (err) {
  Sentry.captureException(err);
  Sentry.flush(2000);
});

Or listen to before the process exits:

process.on('beforeExit', async () => {
    await something();
    process.exit(0); // if you don't close yourself this will run forever
});

https://nodejs.org/docs/latest-v12.x/api/process.html

I believe these event handlers can be sync or async functions.

[ajjindal]

Sorry for late response. I was checking on the recommendation with our tech lead.

Yes, that + onunhandledrejection would be perfect.

[grant]

Yes, that + onunhandledrejection would be perfect.

I'm not sure what you mean by this. With the above suggestion, you can catch all Node exceptions in a function handler.

What do you mean by onunhandledrejection? Where is the exception coming from?

If the exception is not coming from the Functions Framework itself, then can it be caught with the function handler?

[steren]

To be clear: We expect you to be able to use process.on('uncaughtException', function (err) {}); since this is a standard Node.js API that you can access within Cloud Functions

[ajjindal]

oh that makes sense. we use the combination in our Node SDK but your suggestion makes sense. Will love to get process.on.

[steren]

process.on can be used today in your SDK.

[ajjindal]

I must be missing something. Let me discuss internally and get back to the thread here.

[ajjindal]

So, the process.on will work. thanks for that. Our ask around 'onunhandledrejection` is for async handlers. However, if async handlers are not possible, we can skip on that ask.

Thank you for prompt responses.

[grant]

@ajjindal Is there anything else regarding grabbing uncaught exceptions that we can do?

#215 (comment) provides some code samples and links to docs.

If not, can I close this issue?