I've been running ATS at the edge with keepalive enabled. After some digging I found that ATS creates new connections (by default) for all post requests, instead of re-using a connection. The comment in the code looks like this was (is?) because of some race condition inside ATS. I noticed that there is a config option (proxy.config.http.keep_alive_post_out) which enables the connection re-use for post requests, and it seems to work. Does anyone have any knowledge/experience with this configuration option? Or anything about this race condition?

Thomas Jackson