samba - Feb 2018 - [ctdb] Unable to take recovery lock - contention

When the ctdb is starting, the "Unable to take recovery lock -
contention" log will be output all the time.
Which cases will the "unable to take lock" errror be output?
Thanks!

The following the ctdb logs:
2018/02/12 19:38:51.147959 ctdbd[5615]: CTDB starting on node
2018/02/12 19:38:51.528921 ctdbd[6602]: Starting CTDBD (Version 4.6.10) as PID:
6602
2018/02/12 19:38:51.529060 ctdbd[6602]: Created PID file /run/ctdb/ctdbd.pid
2018/02/12 19:38:51.529120 ctdbd[6602]: Listening to ctdb socket
/var/run/ctdb/ctdbd.socket
2018/02/12 19:38:51.529146 ctdbd[6602]: Set real-time scheduler priority
2018/02/12 19:38:51.648117 ctdbd[6602]: Starting event daemon
/usr/libexec/ctdb/ctdb_eventd -e /etc/ctdb/events.d -s /var/run/ctdb/eventd.sock
-P 6602 -l file:/var/log/log.ctdb -d NOTICE
2018/02/12 19:38:51.648390 ctdbd[6602]: connect() failed, errno=2
2018/02/12 19:38:51.693790 ctdb-eventd[6633]: listening on
/var/run/ctdb/eventd.sock
2018/02/12 19:38:51.693893 ctdb-eventd[6633]: daemon started, pid=6633
2018/02/12 19:38:52.648474 ctdbd[6602]: Set runstate to INIT (1)
2018/02/12 19:38:54.505780 ctdbd[6602]: PNN is 1
2018/02/12 19:38:54.574993 ctdbd[6602]: Vacuuming is disabled for persistent
database ctdb.tdb
2018/02/12 19:38:54.576297 ctdbd[6602]: Attached to database
'/var/lib/ctdb/persistent/ctdb.tdb.1' with flags 0x400
2018/02/12 19:38:54.576322 ctdbd[6602]: Ignoring persistent database
'ctdb.tdb.2'
2018/02/12 19:38:54.576339 ctdbd[6602]: Ignoring persistent database
'ctdb.tdb.0'
2018/02/12 19:38:54.576364 ctdbd[6602]: Freeze db: ctdb.tdb
2018/02/12 19:38:54.576393 ctdbd[6602]: Set lock helper to
"/usr/libexec/ctdb/ctdb_lock_helper"
2018/02/12 19:38:54.579527 ctdbd[6602]: Set runstate to SETUP (2)
2018/02/12 19:38:54.881828 ctdbd[6602]: Keepalive monitoring has been started
2018/02/12 19:38:54.881873 ctdbd[6602]: Set runstate to FIRST_RECOVERY (3)
2018/02/12 19:38:54.882020 ctdb-recoverd[7182]: monitor_cluster starting
2018/02/12 19:38:54.882620 ctdb-recoverd[7182]: Initial recovery master set -
forcing election
2018/02/12 19:38:54.882702 ctdbd[6602]: This node (1) is now the recovery master
2018/02/12 19:38:55.882735 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:38:56.902874 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:38:57.885800 ctdb-recoverd[7182]: Election period ended
2018/02/12 19:38:57.886134 ctdb-recoverd[7182]: Node:1 was in recovery mode.
Start recovery process
2018/02/12 19:38:57.886160 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:38:57.886187 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:38:57.886243 ctdb-recoverd[7182]: Set cluster mutex helper to
"/usr/libexec/ctdb/ctdb_mutex_fcntl_helper"
2018/02/12 19:38:57.899722 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:38:57.899763 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:38:57.903138 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:38:58.887310 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:38:58.887353 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:38:58.893531 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:38:58.893571 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:38:58.903314 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:38:59.891024 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:38:59.891080 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:38:59.898336 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:38:59.898397 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:38:59.904710 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:39:00.893673 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:39:00.893741 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:39:00.901094 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:39:00.901152 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:39:00.911007 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:39:01.895044 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:39:01.895106 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:39:01.902379 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:39:01.902451 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:39:01.912054 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:39:02.896539 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:39:02.896597 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:39:02.904674 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:39:02.904736 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:39:02.912896 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:39:03.898495 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:39:03.898548 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:39:03.904876 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:39:03.904929 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:39:03.913736 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED
2018/02/12 19:39:04.899872 ctdb-recoverd[7182]:
../ctdb/server/ctdb_recoverd.c:1267 Starting do_recovery
2018/02/12 19:39:04.899928 ctdb-recoverd[7182]: Attempting to take recovery lock
(/share-fs/export/ctdb/.ctdb/reclock)
2018/02/12 19:39:04.907784 ctdb-recoverd[7182]: Unable to take recovery lock -
contention
2018/02/12 19:39:04.907837 ctdb-recoverd[7182]: Unable to get recovery lock -
retrying recovery
2018/02/12 19:39:04.914048 ctdbd[6602]: CTDB_WAIT_UNTIL_RECOVERED