Make pid_exists() more robust against empty pid argument

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

Let's make sure pid_exists() returns false when the pid is an empty
string.

- 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

Fixes: 3028ce2595c8 ("ovs-lib: Allow "status" command to work as non-root.")

Signed-off-by: Michele Baldessari <michele@acksyn.org>
Signed-off-by: Ben Pfaff <blp@ovn.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/utilities/ovs-lib.in b/utilities/ovs-lib.in
index 0b5f4ce50..fde8194f3 100644
--- a/utilities/ovs-lib.in
+++ b/utilities/ovs-lib.in
@@ -125,7 +125,7 @@ fi
 pid_exists () {
     # This is better than "kill -0" because it doesn't require permission to
     # send a signal (so daemon_status in particular works as non-root).
-    test -d /proc/"$1"
+    test -n "$1" && test -d /proc/"$1"
 }
 
 pid_comm_check () {