Capturing Exception from Service Worker

[coluccini]

I'm trying to track exceptions happening inside a service worker to Sentry. I have a very basic setting and everything seams to be fine, except that the error are never sent (or even tried to be send to sentry).
The code looks something like this:

self.importScripts('https://cdn.ravenjs.com/3.19.1/raven.min.js');
Raven.config('sentryPublicKey').install();

self.addEventListener('install', function(event) {
  try {
    // some actions
  } catch (err) {
    console.log(Raven.isSetup());
    Raven.captureException(err);
  }
});

The console.log(Raven.isSetup()); line always print true, so Raven should be correctly set up at this point. And the line Raven.captureException(err); doesn't show any kind of error, but it doesn't do anything either. There's something that makes sentry not being able to run inside a service worker? Some one knows if there is a way to achieve this?
Thanks a lot!

[kamilogorek]

Hey @coluccini, ServiceWorkers doesn't have an access to XHR APIs, therefore it cannot communicate with an outside world – https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API

It is designed to be fully async; as a consequence, APIs such as synchronous XHR and localStorage can't be used inside a service worker.

I'll look into how this can be handled soon.

[nimishsinghal]

I am also having the same issue. Is there any general practice people follow for error reporting in SW?

[kamilogorek]

@nimishsinghal You can use https://github.com/bevacqua/swivel (or implement it on your own using https://ponyfoo.com/articles/serviceworker-messagechannel-postmessage) to pass a message when an error occurs.

To catch an errors themselves, use onerror or error event inside your ServiceWorker self.onerror = ... or self.addEventListener('error', ...), and when it happens, send a message to the parent (your code) and trigger Raven.captureException or Raven.captureMessage with the data you get from the passed message.

[coluccini]

Mmm but this will work only if the user has the page loaded, but there are situations when you want to track errors without the page being loaded (ex: an error when receiving or trying to show a push notifications). There are no way to track an error using a fetch (get or post) request?

[kamilogorek]

There is, but you need to create payload/urls yourself, as it's outside of SDK scope – https://docs.sentry.io/clientdev/overview/

[coluccini]

Thanks! I'll have a look.

Should I close this issue?

[kamilogorek]

Let's leave it open. I'll try to create a proper doc/feature one day.

[nimishsinghal]

Thanks @kamilogorek @coluccini will try to create custom payloads today

[nimishsinghal]

Hey @kamilogorek,

If we just edit _makeRequest method (https://github.com/getsentry/raven-js/blob/master/src/raven.js#L1884) and use fetch instead of XHR APIs will raven-js work for service workers?

[coluccini]

Yes, but you would leave tons of browser out of compatibility.
Maybe add an new method using fetch that we can use from a service worker?

[nimishsinghal]

Can we use https://github.com/github/fetch so that modern browsers use fetch implementation and use XHR APIs for fallback?

[nimishsinghal]

@kamilogorek @coluccini It is working fine for me, I am able to push errors to sentry by modifying _makeRequest. If the approach is okay and apart from my use case it is a general issue, I will be more than happy to create a PR and move XHR API's to fetch(https://github.com/github/fetch)

[kamilogorek]

There's already a PR for this #1115
I'll try to merge it before the end of the week.

Can we use https://github.com/github/fetch so that modern browsers use fetch implementation and use XHR APIs for fallback?

Not really, it'll increase a total size of raven, which we want to mitigate.