Handle UDP graceful termination

The current logic is to delete a RS if the number of active connections is 0. This makes sense for TCP but for UDP the number of active connections is always 0. This is an issue for DNS queries because the RS will be deleted but the IPVS connection will remain until it expires (5mn by default) and if there are a lot of DNS queries, the port will be reused and queries blackholed. Of course for this to work properly the service needs to continue to serve queries until the connections expire (this works fine with the lameduck option of coredns).

Handle UDP graceful termination
437edead · Laurent Bernaille · 0523ad62 · 437edead
Commit 437edead authored Nov 28, 2018 by Laurent Bernaille
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graceful_termination.go pkg/proxy/ipvs/graceful_termination.go +2 -1

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--- a/pkg/proxy/ipvs/graceful_termination.go
+++ b/pkg/proxy/ipvs/graceful_termination.go
@@ -164,7 +164,8 @@ func (m *GracefulTerminationManager) deleteRsFunc(rsToDelete *listItem) (bool, e
 	}
 	for _, rs := range rss {
 		if rsToDelete.RealServer.Equal(rs) {
-			if rs.ActiveConn != 0 {
+			// Don't delete TCP RS with Active Connections or UDP RS (ActiveConn is always 0 for UDP)
+			if rs.ActiveConn != 0 || (rsToDelete.VirtualServer.Protocol == "UDP" && rs.InactiveConn != 0) {
 				return false, nil
 			}
 			klog.Infof("Deleting rs: %s", rsToDelete.String())