@TI-Admin - Sorry for any confusion. Just trying to help. What I meant was that - “do you have anything in front of your Mattermost instance?” And nginx can be used as a load-balancer as well.
Anyways, coming to the issue, I don’t know what the exact solution here is myself. All we know is that nginx is disconnecting one half of the connection (client-side), and keeping the other half alive(server-side) due to some specific reason. And when this happens, the server connection doesn’t get data and disconnects it.
The blog post I linked to earlier mentions that the idle timeout of the proxy/load-balancer should be half of the idle timeout of the server. But @agriesser, if even that doesn’t help, we’ll need to dig further into this.
Somehow, some nginx setting is causing this to happen.