We've recently upgraded to HAProxy 1.8.3, which we run with `nbthread 4` (we used to run nbproc 4 with older releases). This has generally been good, especially for stick tables & stats.
We terminate SSL and proxy a large number of long-running TCP connections (websockets). When configuration changes (usually a server going up or down), a reload occurs. For many hours, there may be 2-5 active HAProxy instances as the old ones drain. We use hard-stop-after to keep it reasonable. I have noticed that load average gets *very* high while these processes are still present. Our web tier is usually at a load average of 5 with 16 cores. Across the board, load averages go up if stale HAProxy instances are active. I saw as high as 34 with one instance that had 5 instances, and 100% CPU, most of it sys. Even with just 2, the loadavg is double what it is with 1. Terminating the old process immediately brings the load down. Is there a regression in the 1.8 series with SO_REUSEPORT and nbthread (we didn't see this before with nbproc) or somewhere we should start looking? We make (relatively) heavy use of stick tables for DDoS protection purposes and terminate SSL, but aside from that our configuration is pretty vanilla. Nothing changed from 1.7 to 1.8 except changing nbproc to nbthread. Thanks!
