This may be due to this ansible commit changing koji config:

commit ccf122c7422579970e7b1db5434a9182d2107ec3
Author: Kevin Fenzi kevin@scrye.com
Date: Fri Jun 8 00:09:30 2018 +0000

try setting a RLIMIT on koji hub. ticket 6966

diff --git a/roles/koji_hub/templates/hub.conf.j2 b/roles/koji_hub/templates/hub.conf.j2
index 3645e86..e879518 100644
--- a/roles/koji_hub/templates/hub.conf.j2
+++ b/roles/koji_hub/templates/hub.conf.j2
@@ -18,6 +18,7 @@ ProxyPrincipals = HTTP/koji.fedoraproject.org@FEDORAPROJECT.ORG,sigul/sign-bridg
KojiDir = /mnt/koji
MemoryWarnThreshold = 10000
MaxRequestLength = 167772160
+RLIMIT_AS = 1073741824
CheckClientIP = False

# Kerb auth

we may need to up this more...