[Pacemaker] Issues with HA cluster for mysqld

Jake Smith jsmith at argotec.com
Thu Aug 23 17:26:26 EDT 2012 

----- Original Message -----
> From: "David Parker" <dparker at utica.edu>
> To: pacemaker at oss.clusterlabs.org
> Sent: Thursday, August 23, 2012 4:47:11 PM
> Subject: Re: [Pacemaker] Issues with HA cluster for mysqld
> 
> 
> On 08/23/2012 04:19 PM, Jake Smith wrote:
> >> Okay, I think I've almost got this.  I updated my Pacemaker config
> >> and
> >> made a few changes.  I put the MysqlIP and mysqld primitives into
> >> a
> >> resource group called "mysqld-resources", ordered them such that
> >> mysqld
> >> will always wait for MysqlIP to be ready first, and added
> >> constraints
> >> to
> >> make ha1 the preferred host for the mysqld-resources group and ha2
> >> the
> >> failover host.  I also created STONITH devices for both ha1 and
> >> ha2,
> >> and
> >> added constraints to fix the STONIOTH location issues.  My new
> >> constraints section looks like this:
> >>
> >> <constraints>
> >> <rsc_location id="loc-1" rsc="stonith-ha1" node="ha2"
> >> score="INFINITY"/>
> >> <rsc_location id="loc-2" rsc="stonith-ha2" node="ha1"
> >> score="INFINITY"/>
> > Don't need the 2 above as long as you have the 2 negative locations
> > below for stonith locations.  I prefer the negative below because
> > if you ever expanded to greater than 2 nodes the stonith for any
> > node could run on any node but itself
> 
> Good call.  I'll take those out of the config.

One caveaut - only if it's an op-out cluster

> 
> >> <rsc_location id="loc-3" rsc="stonith-ha1" node="ha1"
> >> score="-INFINITY"/>
> >> <rsc_location id="loc-4" rsc="stonith-ha2" node="ha2"
> >> score="-INFINITY"/>
> >> <rsc_location id="loc-5" rsc="mysql-resources" node="ha1"
> >> score="200"/>
> > Don't need the 0 score below either - the 200 above will take care
> > of it.  Pretty sure no location constraint is the same as a 0
> > score location.
> 
> That was based on the example found in the documentation.  If I don't
> have the 0 score entry, will the service still fail over?

Maybe depends on symmetric setting - they wont if you created an opt-in cluster; will if it's a opt-out cluster - but test of course ;-)
Opt-in:
crm_attribute --attr-name symmetric-cluster --attr-value false
Opt-out - setting is true:
crm_attribute --attr-name symmetric-cluster --attr-value true

I prefer to use opt-out and explicitly define nodes where things can't run as opposed to the opposite.

more on that here specifically under 6.2.2 and 6.2.3:
http://www.clusterlabs.org/doc/en-US/Pacemaker/1.0/html/Pacemaker_Explained/ch-constraints.html

> 
> >> <rsc_location id="loc-6" rsc="mysql-resources" node="ha2"
> >> score="0"/>
> >> </constraints>
> >>
> >> Everything seems to work.  I had the virtual IP and mysqld running
> >> on
> >> ha1, and not on ha2.  I shut down ha1 using "poweroff -n" and both
> >> the
> >> virtual IP and mysqld came up on ha2 almost instantly.  When I
> >> powered
> >> ha1 on again, ha2 shut down the the virtual IP and mysqld.  The
> >> virtual
> >> IP moved over instantly; a continuous ping of the IP produced one
> >> "Time
> >> to live exceeded" message and one packet was lost, but that's to
> >> be
> >> expected.  However, mysqld took almost 30 seconds to start up on
> >> ha1
> >> after being stopped on ha2, and I'm not exactly sure why.
> >>
> >> Here's the relevant log output from ha2:
> >>
> >> Aug 23 11:42:48 ha2 crmd: [1166]: info: te_rsc_command: Initiating
> >> action 16: stop mysqld_stop_0 on ha2 (local)
> >> Aug 23 11:42:48 ha2 crmd: [1166]: info: do_lrm_rsc_op: Performing
> >> key=16:1:0:ec1989a8-ff84-4fc5-9f48-88e9b285797c op=mysqld_stop_0 )
> >> Aug 23 11:42:48 ha2 lrmd: [1163]: info: rsc:mysqld:10: stop
> >> Aug 23 11:42:50 ha2 lrmd: [1163]: info: RA output:
> >> (mysqld:stop:stdout)
> >> Stopping MySQL daemon: mysqld_safe.
> >> Aug 23 11:42:50 ha2 crmd: [1166]: info: process_lrm_event: LRM
> >> operation
> >> mysqld_stop_0 (call=10, rc=0, cib-update=57, confirmed=true) ok
> >> Aug 23 11:42:50 ha2 crmd: [1166]: info: match_graph_event: Action
> >> mysqld_stop_0 (16) confirmed on ha2 (rc=0)
> >>
> >> And here's the relevant log output from ha1:
> >>
> >> Aug 23 11:42:47 ha1 crmd: [1243]: info: do_lrm_rsc_op: Performing
> >> key=8:1:7:ec1989a8-ff84-4fc5-9f48-88e9b285797c op=mysqld_monitor_0
> >> )
> >> Aug 23 11:42:47 ha1 lrmd: [1240]: info: rsc:mysqld:5: probe
> >> Aug 23 11:42:47 ha1 crmd: [1243]: info: process_lrm_event: LRM
> >> operation
> >> mysqld_monitor_0 (call=5, rc=7, cib-update=10, confirmed=true) not
> >> running
> >> Aug 23 11:43:36 ha1 crmd: [1243]: info: do_lrm_rsc_op: Performing
> >> key=11:3:0:ec1989a8-ff84-4fc5-9f48-88e9b285797c op=mysqld_start_0
> >> )
> >> Aug 23 11:43:36 ha1 lrmd: [1240]: info: rsc:mysqld:11: start
> >> Aug 23 11:43:36 ha1 lrmd: [1240]: info: RA output:
> >> (mysqld:start:stdout)
> >> Starting MySQL daemon: mysqld_safe.#012(See
> >> /usr/local/mysql/data/mysql.messages for messages).
> >> Aug 23 11:43:36 ha1 crmd: [1243]: info: process_lrm_event: LRM
> >> operation
> >> mysqld_start_0 (call=11, rc=0, cib-update=18, confirmed=true) ok
> >>
> >> So, ha2 stopped mysqld at 11:42:50, but ha1 didn't start mysqld
> >> until
> >> 11:43:36, a full 46 seconds after it was stopped on ha2.  Any
> >> ideas
> >> why
> >> the delay for mysqld was so long, when the MysqlIP resource moved
> >> almost
> >> instantly?
> > Couple thoughts.
> >
> > Are you sure both servers have the same time (in sync)?
> 
> Yep.  They're both using NTP.
> 
> > On HA2 did verify mysqld was actually done stopping at the 11:42:50
> > mark?
> > I don't use mysql so I can't say from experience.
> 
> Yes, I kept checking (with "ps -ef | grep mysqld") every few seconds,
> and it stopped running around that time.  As soon as it stopped
> running
> on ha2, I started checking on ha1 and it was quite a while before
> mysqld
> started.  I knew it was at least 30 seconds, and I believe it was
> actually 42 seconds as the logs indicate.
> 
> > Just curious but do you really want it to failback if it's actively
> > running on ha2?
> 
> Interesting point.  I had just assumed that it was good practice to
> have
> a preferred node for a service, but I guess it doesn't matter.  If I
> don't care which node the services run on, do I just remove the
> location
> constraints for the "mysql-resources" group altogether?

I would say yes.  Usually you also set your default resource stickiness property to something like 100 or 200 which will also help to prevent failback.  If your nodes are identical then you *may* not care which node something runs on - I don't.  I only care that certain resources colocate on the same node but not which node that is.  I don't want resources to move around unless they are failing = better uptime for my services.

One way is to have a location statement like you do with lets say score=100 for ha1.  Then you have a default stickiness of 200.  If you start the resource from stopped it will start on the preferred node in the location statement assuming both nodes are up - ha1. Now assume ha1 failed and your group moved to ha2.  Now you start ha1 back up. The group will have a score of 200 for node ha2 from the stickiness score. ha1 will only have the location score of 100 to run the group.  This will prevent it from moving since ha2 will have the higher score - 200 > 100 - than the preferred node. That's a simplified example but hopefully illustrates the idea.  Scoring can get very complicated!

more on resource stickiness default here:
http://www.clusterlabs.org/doc/en-US/Pacemaker/1.0/html/Pacemaker_Explained/s-resource-options.html

> 
> > Could you include the output of '$crm configure show' next time?  I
> > read that much better/quicker than the xml pacemaker config :-)
> >
> > Jake
> 
> Thanks so much for all of your help, Jake!  I'm new to all of this,
> and
> I really appreciate it.

Np - we've all been there.  I've gotten plenty of help which has gotten me to where I am.  It's a 'pay it forward' community here!

> 
> Here's the requested output:
> 
> root at ha1:~# crm configure show
> node $id="1b48f410-44d1-4e89-8b52-ff23b32db1bc" ha1
> node $id="9790fe6e-67b2-4817-abf4-966b5aa6948c" ha2
> primitive MysqlIP ocf:heartbeat:IPaddr2 \
>          params ip="192.168.25.9" cidr_netmask="32" \
>          op monitor interval="10s"
> primitive mysqld lsb:mysqld
> primitive stonith-ha1 stonith:external/riloe \
>          params hostlist="ha1" ilo_hostname="10.0.1.111"
> ilo_user="Administrator" ilo_password="XXXXXXXX" ilo_can_reset="1"
> ilo_protocol="2.0" ilo_powerdown_method="button"
> primitive stonith-ha2 stonith:external/riloe \
>          params hostlist="ha2" ilo_hostname="10.0.1.112"
> ilo_user="Administrator" ilo_password="XXXXXXXX" ilo_can_reset="1"
> ilo_protocol="2.0" ilo_powerdown_method="button"
> group mysql-resources MysqlIP mysqld
> location loc-1 stonith-ha1 inf: ha2
> location loc-2 stonith-ha2 inf: ha1
> location loc-3 stonith-ha1 -inf: ha1
> location loc-4 stonith-ha2 -inf: ha2
> location loc-5 mysql-resources 200: ha1
> location loc-6 mysql-resources 0: ha2
> property $id="cib-bootstrap-options" \
>          dc-version="1.0.9-74392a28b7f31d7ddc86689598bd23114f58978b"
>          \
>          cluster-infrastructure="Heartbeat" \
>          stonith-enabled="true"
> 

Assuming this is a new setup - any particular reason you're using heartbeat instead of corosync?  Heartbeat is in maintenace mode only I believe they call it - anyway no further development.  Also pacemaker 1.0.9 is pretty old - lots of fixes in the 1.1.x series...

> Also, I verified that STONITH is working.  I unplugged the network
> cable
> on ha1 when the virtual IP and mysqld were running.  ha2 promptly
> took
> over the services and used STONITH to shut down ha1 via iLO.  So,
> that
> part works and flawlessly.  There was once again a delay between the
> mysqld shutdown on ha2 and startup on ha1 after I brought ha1 back
> online, though.  Not as bad as before, about 25 seconds this time.
>  It
> seems that the delay only occurs when the non-preferred node
> relinquishes control of the resources back to their preferred node
> following a failover.  If I stop preferring one node for the
> services,
> this might not be an issue any longer.

hmm seems odd the delay is only in one direction.

> 
>      - Dave
> 
> > _______________________________________________
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> 
> --
> 
> Dave Parker
> Systems Administrator
> Utica College
> Integrated Information Technology Services
> (315) 792-3229
> Registered Linux User #408177
> 
> 
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