I'm experiencing an issue while applying load to uwsgi instances placed behind an Amazon Elastic Load Balancer. Specifically, there is a strange latency that appears to surface when applying load to the ELB. After a session of wireshark, uwsgitop, and other debugging methods, I've determined that ELB is sending out additional socket requests to the backend that are not generated from the client and not from ELB's internal health check. There's a 3rd mysterious source of load that opens a socket and closes a socket to the uwsgi backend every few seconds. Looking at uwsgitop, I can frequently see workers in a "busy" state even when the client is not generating load. Understandably, some of the requests going to uwsgi will be ELB health check requests, but there shouldn't be anything else beyond that.

I suspect that this mysterious opening and closing of sockets consumes a spot in the listen queue and is the cause for the latency I'm experiencing. Does this sound familiar and has anyone else experienced it? I've already opened a case with Amazon Web Services and awaiting a response, but I thought I'd reach out here as well to see if this is a known issue. If I take ELB out of the equation and just apply load from the client directly to uwsgi, everything works great and there is no increase in latency.