Around 10.15 UTC this morning I started getting errors resulting in failed requests. Had a few minutes of 500 errors. In the logs the error was EAI_AGAIN from a NodeJS fetch call. So the app was trying to make a https fetch, and failed.
Googling that error I found:
EAI_AGAIN appears to be a system error in the context of a failed DNS resolution. That rather points to whatever system resolver you have configured on your system
Which got me thinking: what DNS resolver is configured on the fly apps? How do they lookup DNS records? Presumably the host server handles it?
Were there any issues with that service in lhr today?
I haven’t changed any DNS entries or updated the app. It just stopped working. Then started again, presumably when the DNS could resolve again.