Worker (on bundled plan) getting frequent 1101 errors - "Canceled" and "Exception" worker log entry and response

We keep seeing Error 1101’s intermittently on requests to our API, and they’re not that long-running. We use the bundled workers model. Timeouts don’t exist on our origin/server-side.

When looking at logs for workers, we see an instance like this - what does it mean?

Cancelled is when the client has disconnected.

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Error 1101: Rendering error

Common cause

A Cloudflare Worker throws a runtime JavaScript exception.


Provide appropriate issues details to Cloudflare Support.

We’ve got try/catches around our code (support noted that) - no errors are being logged.

For calls that are not long in terms of duration, this happens all over the place - why?

@KentonVarda any thoughts?

Interesting. As I mentioned before, the mostly-blank line in the log represents the execution of the app you have installed. In this case, that line says “Exception” while the log line for your own worker says “Canceled”. That suggests to me that the app threw an exception. Since the app acts as a proxy before your worker, when the app throws an exception, it then disconnects from your worker, hence your worker is canceled.


FWIW, part of the reason we put Apps with Workers on hold for a while is because situations like these are really difficult and frustrating to deal with at the moment. Neither you nor the app developer have a lot of visibility into why the app is failing. This is really our fault, not yours nor the app developer’s. This isn’t an experience we’re happy with, but we’re not quite ready yet to dedicate the time needed to make apps work well. (We’re getting closer, though.)

I believe the app you are using also allows you the alternative of integrating with them directly in your own worker. That might be a better option for now, as that way you’d be able to see the exception being thrown and fix the code directly.


Noted, thanks @KentonVarda

On the direct integration of bringing the app-code into our own worker - did you mean this Node SDK?

No, I meant here: GitHub - Moesif/moesif-cloudflare: Moesif SDK for Cloudflare

“Install via Cloudflare Workers (Custom install) using Cloudflare Dashboard”

However, on another look, this might be kind of hard. You’d essentially need to merge Moesif’s code with your own Worker, by finding where they do fetch(request) and replacing it with a call to your own worker. I guess don’t take this path if it isn’t clear to you how that would work…

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