Clearing browser cookies fixes "could not find an instance to route to" 503 error


I was trying to deploy a Ruby on Rails app, and while troubleshooting the deploy, I ended up deleting and recreating the app. The second time I created it, the app deployed and seemed to work, but I couldn’t access it from Chrome (the browser I had been using to test) - it would try for a while and eventually fail with this error in the logs:

2022-12-24T05:45:03Z proxy[c9c719b2] iad [error]Error: could not find an instance to route to

(fly-request-id: 01GN1AH1V8NDGTNRPR3QCP901N-iad)

Finally I realized I was able to access it using curl and other browsers, which led me to clear my cookies (and then it worked) - despite the fact that Chrome didn’t think I had any cookies associated with this website.

I have a feeling this might be similar to a couple other threads that I found while trying to troubleshoot:

  • Setting my app's name causes my app not to work - The fact that it seemed to correlate with setting the app name makes me think it could’ve been related to browser cookies/cache as well. I wonder if they were trying to name it the same thing each time, and the browser might have had cookies associated with it. When they used a randomly generated app name, it was different from any other website name and wouldn’t have had any cookies.

  • Error: could not find an instance to route to - Though mine was failing with a 503 response code instead of 502.

Anyway my question is, whether or not my issue is related to either of the above, how is it possible that browser cookies led to this error? Thanks for any help/insight!