[ClusterLabs] Mysql slave did not start replication after failure, and read-only IP also remained active on the much outdated slave
Ken Gaillot
kgaillot at redhat.com
Mon Aug 22 14:11:34 UTC 2016
On 08/22/2016 07:24 AM, Attila Megyeri wrote:
> Hi Andrei,
>
> I waited several hours, and nothing happened.
And actually, we can see from the configuration you provided that
cluster-recheck-interval is 2 minutes.
I don't see anything about stonith; is it enabled and tested? This looks
like a situation where stonith would come into play. I know that power
fencing can be rough on a MySQL database, but perhaps intelligent
switches with network fencing would be appropriate.
The "Corosync main process was not scheduled" message is the start of
the trouble. It means the system was overloaded and corosync didn't get
any CPU time, so it couldn't maintain cluster communication.
Probably the most useful thing would be to upgrade to a recent version
of corosync+pacemaker+resource-agents. Recent corosync versions run with
realtime priority, which makes this much less likely.
Other than that, figure out what the load issue was, and try to prevent
it from recurring.
I'm not familiar enough with the RA to comment on its behavior. If you
think it's suspect, check the logs during the incident for messages from
the RA.
> I assume that the RA does not treat this case properly. Mysql was running, but the "show slave status" command returned something that the RA was not prepared to parse, and instead of reporting a non-readable attribute, it returned some generic error, that did not stop the server.
>
> Rgds,
> Attila
>
>
> -----Original Message-----
> From: Andrei Borzenkov [mailto:arvidjaar at gmail.com]
> Sent: Monday, August 22, 2016 11:42 AM
> To: Cluster Labs - All topics related to open-source clustering welcomed <users at clusterlabs.org>
> Subject: Re: [ClusterLabs] Mysql slave did not start replication after failure, and read-only IP also remained active on the much outdated slave
>
> On Mon, Aug 22, 2016 at 12:18 PM, Attila Megyeri
> <amegyeri at minerva-soft.com> wrote:
>> Dear community,
>>
>>
>>
>> A few days ago we had an issue in our Mysql M/S replication cluster.
>>
>> We have a one R/W Master, and a one RO Slave setup. RO VIP is supposed to be
>> running on the slave if it is not too much behind the master, and if any
>> error occurs, RO VIP is moved to the master.
>>
>>
>>
>> Something happened with the slave Mysql (some disk issue, still
>> investigating), but the problem is, that the slave VIP remained on the slave
>> device, even though the slave process was not running, and the server was
>> much outdated.
>>
>>
>>
>> During the issue the following log entries appeared (just an extract as it
>> would be too long):
>>
>>
>>
>>
>>
>> Aug 20 02:04:07 ctdb1 corosync[1056]: [MAIN ] Corosync main process was
>> not scheduled for 14088.5488 ms (threshold is 4000.0000 ms). Consider token
>> timeout increase.
>>
>> Aug 20 02:04:07 ctdb1 corosync[1056]: [TOTEM ] A processor failed, forming
>> new configuration.
>>
>> Aug 20 02:04:34 ctdb1 corosync[1056]: [MAIN ] Corosync main process was
>> not scheduled for 27065.2559 ms (threshold is 4000.0000 ms). Consider token
>> timeout increase.
>>
>> Aug 20 02:04:34 ctdb1 corosync[1056]: [TOTEM ] A new membership (xxx:6720)
>> was formed. Members left: 168362243 168362281 168362282 168362301 168362302
>> 168362311 168362312 1
>>
>> Aug 20 02:04:34 ctdb1 corosync[1056]: [TOTEM ] A new membership (xxx:6724)
>> was formed. Members
>>
>> ..
>>
>> Aug 20 02:13:28 ctdb1 corosync[1056]: [MAIN ] Completed service
>> synchronization, ready to provide service.
>>
>> ..
>>
>> Aug 20 02:13:29 ctdb1 attrd[1584]: notice: attrd_trigger_update: Sending
>> flush op to all hosts for: readable (1)
>>
>> …
>>
>> Aug 20 02:13:32 ctdb1 mysql(db-mysql)[10492]: INFO: post-demote notification
>> for ctdb1
>>
>> Aug 20 02:13:32 ctdb1 IPaddr2(db-ip-master)[10490]: INFO: IP status = ok,
>> IP_CIP=
>>
>> Aug 20 02:13:32 ctdb1 crmd[1586]: notice: process_lrm_event: LRM operation
>> db-ip-master_stop_0 (call=371, rc=0, cib-update=179, confirmed=true) ok
>>
>> Aug 20 02:13:32 ctdb1 IPaddr2(db-ip-slave)[10620]: INFO: Adding inet address
>> xxx/24 with broadcast address xxxx to device eth0
>>
>> Aug 20 02:13:32 ctdb1 IPaddr2(db-ip-slave)[10620]: INFO: Bringing device
>> eth0 up
>>
>> Aug 20 02:13:32 ctdb1 IPaddr2(db-ip-slave)[10620]: INFO:
>> /usr/lib/heartbeat/send_arp -i 200 -r 5 -p
>> /usr/var/run/resource-agents/send_arp-xxx eth0 xxx auto not_used not_used
>>
>> Aug 20 02:13:32 ctdb1 crmd[1586]: notice: process_lrm_event: LRM operation
>> db-ip-slave_start_0 (call=377, rc=0, cib-update=180, confirmed=true) ok
>>
>> Aug 20 02:13:32 ctdb1 crmd[1586]: notice: process_lrm_event: LRM operation
>> db-ip-slave_monitor_20000 (call=380, rc=0, cib-update=181, confirmed=false)
>> ok
>>
>> Aug 20 02:13:32 ctdb1 crmd[1586]: notice: process_lrm_event: LRM operation
>> db-mysql_notify_0 (call=374, rc=0, cib-update=0, confirmed=true) ok
>>
>> Aug 20 02:13:32 ctdb1 attrd[1584]: notice: attrd_trigger_update: Sending
>> flush op to all hosts for: master-db-mysql (1)
>>
>> Aug 20 02:13:32 ctdb1 attrd[1584]: notice: attrd_perform_update: Sent
>> update 1622: master-db-mysql=1
>>
>> Aug 20 02:13:32 ctdb1 crmd[1586]: notice: process_lrm_event: LRM operation
>> db-mysql_demote_0 (call=384, rc=0, cib-update=182, confirmed=true) ok
>>
>> Aug 20 02:13:33 ctdb1 mysql(db-mysql)[11160]: INFO: Ignoring post-demote
>> notification for my own demotion.
>>
>> Aug 20 02:13:33 ctdb1 crmd[1586]: notice: process_lrm_event: LRM operation
>> db-mysql_notify_0 (call=387, rc=0, cib-update=0, confirmed=true) ok
>>
>> Aug 20 02:13:33 ctdb1 mysql(db-mysql)[11185]: ERROR: check_slave invoked on
>> an instance that is not a replication slave.
>>
>> Aug 20 02:13:33 ctdb1 crmd[1586]: notice: process_lrm_event: LRM operation
>> db-mysql_monitor_7000 (call=390, rc=0, cib-update=183, confirmed=false) ok
>>
>> Aug 20 02:13:33 ctdb1 ntpd[1560]: Listen normally on 16 eth0 xxxx. UDP 123
>>
>> Aug 20 02:13:33 ctdb1 ntpd[1560]: Deleting interface #12 eth0, xxx#123,
>> interface stats: received=0, sent=0, dropped=0, active_time=2637334 secs
>>
>> Aug 20 02:13:33 ctdb1 ntpd[1560]: peers refreshed
>>
>> Aug 20 02:13:33 ctdb1 ntpd[1560]: new interface(s) found: waking up resolver
>>
>> Aug 20 02:13:40 ctdb1 mysql(db-mysql)[11224]: ERROR: check_slave invoked on
>> an instance that is not a replication slave.
>>
>> Aug 20 02:13:47 ctdb1 mysql(db-mysql)[11263]: ERROR: check_slave invoked on
>> an instance that is not a replication slave.
>>
>>
>>
>> And from this time, the last two lines repeat every 7 seconds (mysql
>> monitoring interval)
>>
>>
>>
>>
>>
>> The expected behavior was that the slave (RO) VIP should have been moved to
>> the master, as the secondary db was outdated.
>>
>> Unfortunately I cannot recall what crm_mon was showing when the issue was
>> present, but I am sure that the RA did not handle the situation properly.
>>
>>
>>
>> Placing the slave node into standby and the online resolved the issue
>> immediately (Slave started to sync, and in a few minutes it catched up the
>> master).
>>
>>
>>
>>
>>
>> Here is the relevant config from the configuration:
>>
>>
>>
>>
>>
>> primitive db-ip-master ocf:heartbeat:IPaddr2 \
>>
>> params lvs_support="true" ip="XXX" cidr_netmask="24"
>> broadcast="XXX" \
>>
>> op start interval="0" timeout="20s" on-fail="restart" \
>>
>> op monitor interval="20s" timeout="20s" \
>>
>> op stop interval="0" timeout="20s" on-fail="block"
>>
>>
>>
>> primitive db-ip-slave ocf:heartbeat:IPaddr2 \
>>
>> params lvs_support="true" ip="XXX" cidr_netmask="24"
>> broadcast="XXX" \
>>
>> op start interval="0" timeout="20s" on-fail="restart" \
>>
>> op monitor interval="20s" timeout="20s" \
>>
>> op stop interval="0" timeout="20s" on-fail="block" \
>>
>> meta target-role="Started"
>>
>>
>>
>> primitive db-mysql ocf:heartbeat:mysql \
>>
>> params binary="/usr/bin/mysqld_safe"
>> config="/etc/mysql/my.cnf" datadir="/var/lib/mysql" user="mysql"
>> pid="/var/run/mysqld/mysqld.pid" socket="/var/run/mysqld/mysqld.sock"
>> test_passwd="XXX" test_table="XXX" test_user="XXX" replication_user="XXX"
>> replication_passwd="XXX" additional_parameters="--skip-slave-start" \
>>
>> op start interval="0" timeout="240s" on-fail="restart" \
>>
>> op stop interval="0" timeout="120s" on-fail="block" \
>>
>> op monitor interval="7" timeout="30s" on-fail="restart"
>> OCF_CHECK_LEVEL="1" \
>>
>> op promote interval="0" timeout="120" on-fail="restart" \
>>
>> op demote interval="0" timeout="120" on-fail="block"
>>
>>
>>
>> ms mysql db-mysql \
>>
>> meta notify="true" master-max="1" clone-max="2"
>> target-role="Started" is-managed="true"
>>
>>
>>
>> location db-ip-m-1 db-ip-master 0: ctdb1
>>
>> location db-ip-m-2 db-ip-master 0: ctdb2
>>
>> location db-ip-s-1 db-ip-slave 0: ctdb1
>>
>> location db-ip-s-2 db-ip-slave 0: ctdb2
>>
>> location db-ip-s-readable db-ip-slave \
>>
>> rule $id="rule-no-reader-slave" -inf: readable lt 1
>>
>
> How long did you wait? Conditions are reevaluated every
> cluster-recheck-interval which is 15 minutes by default.
>
>> location db-mysql-loc-1 mysql 100: ctdb1
>>
>> location db-mysql-loc-2 mysql 100: ctdb2
>>
>>
>>
>> colocation db-ip-slave-master -50: db-ip-slave db-ip-master
>>
>> colocation db-ip-with-master inf: db-ip-master mysql:Master
>>
>> colocation db-slave-on-db inf: db-ip-slave mysql
>>
>> order master-after-db inf: mysql db-ip-master
>>
>> order slave-after-db inf: mysql db-ip-slave
>>
>>
>>
>> property $id="cib-bootstrap-options" \
>>
>> dc-version="1.1.10-42f2063" \
>>
>> cluster-infrastructure="corosync" \
>>
>> symmetric-cluster="false" \
>>
>> cluster-recheck-interval="2m" \
>>
>> no-quorum-policy="stop" \
>>
>> stop-orphan-resources="false" \
>>
>> start-failure-is-fatal="false" \
>>
>> maintenance-mode="false"
>>
>> property $id="mysql_replication" \
>>
>> db-mysql_REPL_INFO="ctdb2|mysql-bin.002928|107"
>>
>> rsc_defaults $id="rsc-options" \
>>
>> resource-stickiness="0"
>>
>>
>>
>>
>>
>>
>>
>> Do you have any hints what could have gone wrong, and how we could avoid
>> such issues in the future?
>>
>>
>>
>> Versions:
>>
>> Ubuntu Trusty Tahr
>>
>> Pacemaker 1.1.10
>>
>> Corosync 2.3.3
>>
>> Resource agents 3.9.3
>>
>>
>>
>>
>>
>> Thanks a lot in advance,
>>
>>
>>
>> Attila
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