This issue bothered me for a couple of frustrating hours. I have a Laravel setup on the App platform, using my own container images, but all fairly standard and similar to this DO tutorial in terms of containers.
So I basically have an nginx container talking to a php-fpm container on port 9000. This all works fine in docker-compose, but not on App platform.
The problem was that for longer outputs, especially json, the response just ‘froze’ after about 1500bytes. This made me think it was a buffering issue.
While debugging I connected to the php-fpm server directly using this guide. This worked fine, for outputs of any size.
In the end I found out that there is a nginx directive to disable fastcgi buffering, which resolved the issue.
However I don’t understand why this problem started, and I don’t know whether disabling this buffering may have other (performance?) drawbacks.