mod_cluster in JBCS httpd 2.4 experiences issues with low smax setting

Issue

• We are moving from httpd 2.2 to JBCS httpd 2.4. smax is set low in our modcluster configuration. And now with light load we see connections immediately fail:

[Tue Apr 21 10:20:41.123443 2020] [:debug] [pid 27147:tid 139853093992192] mod_proxy_cluster.c(2479): proxy: byrequests balancer DONE (http:///127.0.0.1:8080)
[Tue Apr 21 10:20:41.123456 2020] [proxy:debug] [pid 27147:tid 139853093992192] proxy_util.c(1919): AH00924: worker http:///127.0.0.1:8080 shared already initialized
[Tue Apr 21 10:20:41.123460 2020] [proxy:debug] [pid 27147:tid 139853093992192] proxy_util.c(1976): AH00926: worker http:///127.0.0.1:8080 local already initialized
[Tue Apr 21 10:20:41.123464 2020] [proxy:debug] [pid 27147:tid 139853093992192] mod_proxy.c(1254): [client 127.0.0.1:40760] AH01143: Running scheme balancer handler (attempt 0)
[Tue Apr 21 10:20:41.125726 2020] [proxy:error] [pid 27147:tid 139853093992192] (70007)The timeout specified has expired: AH00941: HTTP: failed to acquire connection for ()