[ovs-dev] [PATCH] Make pidfile_is_running more robust against empty pidfiles

[Michele Baldessari]

In some of our destructive testing of ovn-dbs inside containers managed
by pacemaker we reached a situation where /var/run/openvswitch had
empty .pid files. The current code does not deal well with them
and pidfile_is_running() returns true in such a case and this confuses
the OCF resource agent.

- Before this change:
Inside a container run:
  killall ovsdb-server;
  echo -n '' > /var/run/openvswitch/ovnnb_db.pid; echo -n '' > /var/run/openvswitch/ovnsb_db.pid

We will observe that the cluster is unable to ever recover because
it believes the ovn processes to be running when they really aren't and
eventually just fails:
 podman container set: ovn-dbs-bundle [192.168.24.1:8787/rhosp15/openstack-ovn-northd:pcmklatest]
   ovn-dbs-bundle-0     (ocf::ovn:ovndb-servers):       Master controller-0
   ovn-dbs-bundle-1     (ocf::ovn:ovndb-servers):       Stopped controller-1
   ovn-dbs-bundle-2     (ocf::ovn:ovndb-servers):       Slave controller-2

- After this change the cluster is able to recover from this state and
correctly start the resource:
 podman container set: ovn-dbs-bundle [192.168.24.1:8787/rhosp15/openstack-ovn-northd:pcmklatest]
   ovn-dbs-bundle-0     (ocf::ovn:ovndb-servers):       Master controller-0
   ovn-dbs-bundle-1     (ocf::ovn:ovndb-servers):       Slave controller-1
   ovn-dbs-bundle-2     (ocf::ovn:ovndb-servers):       Slave controller-2

Signed-off-by: Michele Baldessari <michele at acksyn.org>
---
 ovn/utilities/ovn-ctl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ovn/utilities/ovn-ctl b/ovn/utilities/ovn-ctl
index 7e5cd469c83c..65f03e28ddba 100755
--- a/ovn/utilities/ovn-ctl
+++ b/ovn/utilities/ovn-ctl
@@ -35,7 +35,7 @@ ovn_northd_db_conf_file="$etcdir/ovn-northd-db-params.conf"
 
 pidfile_is_running () {
     pidfile=$1
-    test -e "$pidfile" && pid=`cat "$pidfile"` && pid_exists "$pid"
+    test -e "$pidfile" && [ -s "$pidfile" ] && pid=`cat "$pidfile"` && pid_exists "$pid"
 } >/dev/null 2>&1
 
 stop_nb_ovsdb() {
-- 
2.21.0