[Pacemaker] Required resources for stateful clones (Daniel Bozeman)
Eamon Roque
Eamon.Roque at lex-com.net
Fri May 20 10:38:29 EDT 2011
Hi,
> # postgresql.conf on both servers
> hot_standby = true
> wal_level = hot_standby
> max_wal_senders = # not 0
>
> # recovery.conf on both servers
> standby_mode = 'on'
> primary_conninfo = 'host=[hostname]'
> trigger_file = '/tmp/trigger'
>
> Then all you have to do is rename recovery.conf on one server to
> recovery.done to make it master. Start postgres and streaming
> replication will begin (once you rebase). Should the master go down,
> have Pacemaker touch the trigger file on the standby server and
> restart postgres. This will move recovery.conf to recovery.done and
> the standby will be master.
>
> When you are ready to recover the old master, move recovery.done to
> recovery.conf, rebase, and start postgres. Pgpool has C and SQL
> functions you can install that will allow you to perform online
> recovery (rebasing the standby without shutting down the master).
I've set up streaming replication by hand already. I was confused about
the trigger.file and the recovery.conf on the slave that would be promoted
to master.
Be that as it may, failover wasn't really my problem (failing over to the
slave or bringing the master up (as a slave) afterwards). It worked for
me, and the was able to modify the database without problems, even having
the recovery.conf present when I "touched" the trigger file. This file was
processed and renamed aftwards.
I'm still not quite sure why the cluster could manage my pgsql resource
and still be able to transfer control over to my testing agent (via
ocf-tester" without causing problems.
I appreciate your ruby script, I have one in bash that works pretty well.
;)
Thanks
Éamon
>
> Here is an example rebase script written in Ruby. It is easy to find
> them written in shell script as well, but this script should be very
> easy to translate as it is nothing but system calls.
>
> #!/usr/bin/env ruby
> # performs rebase from current machine
> # to machine "to_host"
>
> # remote host
> host = 'ha2'
>
> print 'recovering...'
> system("ssh -T #{host} /etc/init.d/postgresql stop")
> system("psql -U postgres -c \"SELECT pg_start_backup('backup',
> true)\" postgres")
> system("rsync --exclude server.key --exclude server.crt --exclude
> pg_xlog --exclude recovery.conf --exclude recovery.done --exclude
> postmaster.pid --exclude postgresql.pid --exclude \"pg_log/*\" --
> exclude \"pg_hba.conf\" --exclude \"postgresql.conf\" --recursive --
> times --compress --perms --links --delete /var/lib/postgresql/9.0/
> main/ postgres@#{host}:/var/lib/postgresql/9.0/main/")
> system("psql -U postgres -c \"SELECT pg_stop_backup()\" postgres")
> system("rsync -av /var/lib/postgresql/9.0/main/pg_xlog/ postgres@#
> {host}:/var/lib/postgresql/9.0/main/pg_xlog/")
> system("ssh -T #{host} mv /var/lib/postgresql/9.0/main/
> recovery.done /var/lib/postgresql/9.0/main/recovery.conf")
> system("ssh -T #{host} /etc/init.d/postgresql start")
>
> Is this a postgres mailing list or something? ;)
>
> See one inline comment below.
>
> Take care,
>
> Daniel
>
> On May 20, 2011, at 9:04 AM, Eamon Roque wrote:
>
> >
> > > On Fri, May 20, 2011 at 7:09 AM, Eamon Roque <Eamon.Roque at lex-
> com.net>wrote:
> > >
> > > >
> > > > >
> > > > > On Fri, May 20, 2011 at 3:42 AM, Eamon Roque
<Eamon.Roque at lex-com.net
> > > > >wrote:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > >
> > > > > > >> On Thu, May 19, 2011 at 5:05 AM, Eamon Roque <
> > > > Eamon.Roque at lex-com.net
> > > > > > >wrote:
> > > > > >
> > > > > > >> Hi,
> > > > > > >>
> > > > > > >> I've put together a cluster of two nodes running a
> databank without
> > > > > > shared
> > > > > > >> storage. Both nodes replicate data between them, which
> is taken care
> > > > of
> > > > > > by
> > > > > > >> the databank itself.
> > > > > > >>
> > > > > > >> I have a resource for the databank and ip. I then
> created a stateful
> > > > > > clone
> > > > > > >> from the databank resource. I created colocation rules
> joining the
> > > > > > >> databank-ms-clone and ip:
> > > > > > >>
> > > > > > >> node pgsqltest1
> > > > > > >> node pgsqltest2
> > > > > > >> primitive Postgres-IP ocf:heartbeat:IPaddr2 \
> > > > > > >> params ip="10.19.57.234" cidr_netmask="32" \
> > > > > > >> op monitor interval="30s" \
> > > > > > >> meta is-managed="false"
> > > > > > >> primitive resPostgres ocf:heartbeat:pgsql \
> > > > > > >> params pgctl="/opt/PostgreSQL/9.0/bin/pg_ctl"
> > > > > > >>pgdata="/opt/PostgreSQL/9.0/data" psql="/opt/PostgreSQL/
> 9.0/bin/psql"
> > > > > > >> pgdba="postgres" \
> > > > > > >> op monitor interval="1min" \
> > > > > > >> meta is-managed="false"
> > > > > > >> ms msPostgres resPostgres \
> > > > > > >> meta master-max="1" master-node-max="1"
clone-max="2"
> > > > > > >> clone-node-max="1" notify="true" target-role="started"
> > > > > > >> colocation colPostgres inf: Postgres-IP msPostgres:Master
> > > > > > >> order ordPostgres inf: msPostgres:promote Postgres-IP:start
> > > > > > >> property $id="cib-bootstrap-options" \
> > > > > > >> dc-version="1.1.
> 2-2e096a41a5f9e184a1c1537c82c6da1093698eb5"
> > > > \
> > > > > > >> cluster-infrastructure="openais" \
> > > > > > >> expected-quorum-votes="2" \
> > > > > > >> stonith-enabled="false" \
> > > > > > >> no-quorum-policy="ignore" \
> > > > > > >> last-lrm-refresh="1302707146"
> > > > > > >> rsc_defaults $id="rsc-options" \
> > > > > > >> resource-stickiness="200"
> > > > > > >> op_defaults $id="op_defaults-options" \
> > > > > > >> record-pending="false"
> > > > > > >>
> > > > > > >> The normal postgres agent doesn't support this
functionality, but
> > > > I've
> > > > > > put
> > > > > > >> together my own using the mysql agent as a model.
> Before running the
> > > > > > script
> > > > > > >> through ocf-tester, I unmanage the postgres resource.
> > > > > > >>
> > > > > >
> > > > > > > Could you show how you implemented promote/demote for pgsql?
> > > > > >
> > > > > > Sure, let's start with the ultra-simple "promote" function:
> > > > > >
> > > > > > #
> > > > > > # These variables are higher up in the file, but they will
probably
> > > > help
> > > > > > with understanding the error of
> > > > > > # my ways.
> > > > > >
> > > > > > CRM_MASTER="${HA_SBIN_DIR}/crm_master"
> > > > > > ATTRD_UPDATER="${HA_SBIN_DIR}/attrd_updater"
> > > > > >
> > > > > > pgsql_promote() {
> > > > > > local output
> > > > > > local rc
> > > > > > local CHECK_PG_SQL
> > > > > > local COMPLETE_STANDBY_QUERY
> > > > > > local PROMOTE_SCORE_HIGH
> > > > > > local MOD_PSQL_M_FORMAT
> > > > > >
> > > > > >
> > > > > > PROMOTE_SCORE_HIGH=1000
> > > > > > CHECK_PG_SQL="SELECT pg_is_in_recovery()"
> > > > > > MOD_PSQL_M_FORMAT="$OCF_RESKEY_psql -Atc"
> > > > > > COMPLETE_STANDBY_QUERY="$MOD_PSQL_M_FORMAT
> \"$CHECK_PG_SQL\""
> > > > > >
> > > > > > output=$(su - $OCF_RESKEY_pgdba -c
"$COMPLETE_STANDBY_QUERY"
> > > > 2>&1)
> > > > > > echo $output
> > > > > >
> > > > > > rc=$?
> > > > > >
> > > > > > case $output in
> > > > > > f)
> > > > > > ocf_log debug "PostgreSQL Node is
running in
> > > > Master
> > > > > > mode..."
> > > > > > return $OCF_RUNNING_MASTER
> > > > > > ;;
> > > > > >
> > > > > > t)
> > > > > > ocf_log debug "PostgreSQL Node is in
> > > > Hot_Standby
> > > > > > mode..."
> > > > > > return $OCF_SUCCESS
> > > > > > ;;
> > > > > >
> > > > > > *)
> > > > > > ocf_log err "Critical error in
> $CHECK_PG_SQL:
> > > > > > $output"
> > > > > > return $OCF_ERR_GENERIC
> > > > > > ;;
> > > > > > esac
> > > > > >
> > > > > > #
> > > > > > # "Real" promotion is handled here.
> > > > > > # The trigger file is created and we check for
> "recovery.conf" on the
> > > > host.
> > > > > > # If we can't find it, then the file will be copied from
> the HA-Config
> > > > into
> > > > > > postgres' data folder.
> > > > > > #
> > > > > >
> > > > > > if ! touch $OCF_RESKEY_trigger_file; then
> > > > > > ocf_log err "$OCF_RESKEY_trigger_file could not
becreated!"
> > > > > > return $OCF_ERR_GENERIC
> > > > > > fi
> > > > > >
> > > > > > if [ ! -f $OCF_RESKEY_recovery_conf ]; then
> > > > > > ocf_log err "$OCF_RESKEY_recovery_conf doesn't exist!"
> > > > > > cp $OCF_RESKEY_recovery_conf_ersatz $OCF_RESKEY_pgdata
> > > > > > return $OCF_SUCCESS
> > > > > > fi
> > > > >
> > > > >
> > > > > Why do you need this? As far as I know when you switch
> standby database
> > > > to
> > > > > primary using trigger file recovery.conf gets renamed to
> recovery.done.
> > > > If
> > > > > you rename it back DB will be put into standby mode after
> restart.We are
> > > > > talking about streaming replication, right?
> > > > >
> > > > >
> > > > Right. The order is wrong. According to the Binary Replication
> tutorial on
> > > > the postgres wiki, when I perform a failover with a trigger
> file, it wants
> > > > to find a "recovery.conf", which it then processes (checking
> the archive for
> > > > missing updates etc.) and renames (after noticing the trigger
file).
> > > >
> > > > I assumed that this would work in exactly the same way with
Streaming
> > > > Replication.
> > > >
> > > > Am I wrong?
> > >
> > >
> > > I think so. You have to have recovery.conf when you start your
> standby, not
> > > master. Actually instance that has recovery.conf always tries to
start as
> > > standby. You have to have master's IP address there and path to
> archived log
> > > files.
> > >
> > >
> >
> > So the failover behavior in binary replication and streaming
> replication is different? Or is the wiki entry just antiquated?
>
> "Binary replication" simply refers to streaming replication between
> two (binary) servers. This is a bit misleading, as it may lead you
> to believe it is a WAL-shipping or shared storage replication
> method, but it is not. The information I have provided above should
> be all you need to set up streaming/binary replication (other than
> properly configuring your pg_hba.conf
>
> >
> > > >
> > > >
> > > > > >
> > > > > >
> > > > > > # If both file exist or can be created, then the failover fun
can
> > > > start.
> > > > > >
> > > > > > ocf_log info "$OCF_RESKEY_trigger_file was created."
> > > > > > ocf_log info "$OCF_RESKEY_recovery_conf exists and can be
> copied to the
> > > > > > correct location."
> > > > > >
> > > > > > # Sometimes, the master needs a bit of time to take the reins.
So...
> > > > > >
> > > > > > while :
> > > > > > do
> > > > > > pgsql_monitor warn
> > > > > > rc=$?
> > > > > >
> > > > > > if [ $rc -eq $OCF_RUNNING_MASTER ]; then
> > > > > > break;
> > > > > > fi
> > > > > >
> > > > > > ocf_log debug "Postgres Server could not be promoted.
Please
> > > > > > wait..."
> > > > > >
> > > > > > sleep 1
> > > > > >
> > > > > > done
> > > > > >
> > > > > > ocf_log info "Postgres Server has been promoted. Please check
on the
> > > > > > previous master."
> > > > > >
> > > > > > #################################
> > > > > > #Attributes Update: #
> > > > > > #################################
> > > > > >
> > > > > > $ATTRD_UPDATER -n $PGSQL_STATUS_NAME -v \"PRI\" || exit $(echo
"Eh!
> > > > > > Attrd_updater is not working!")
> > > > > >
> > > > > > #############################################
> > > > > > # Resource stickiness pumped up to 1000 : #
> > > > > > #############################################
> > > > > >
> > > > > > $CRM_MASTER -v $PROMOTE_WERT_HOCH || exit $(echo
> "crm_master could not
> > > > > > change the Master's status!")
> > > > > >
> > > > > > ############
> > > > > > # Success! #
> > > > > > ############
> > > > > >
> > > > > > return $OCF_SUCCESS
> > > > > >
> > > > > > }
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
>
######################################################################################################
> > > > > >
> > > > > > Thanks!
> > > > > >
> > > > > >
> > > > > And what about demote? Switching standby into primary using
> trigger files
> > > > > changes TIMELINE in the DB and that invalidates all other
standby
> > > > databases
> > > > > as well as previous master database. After that you have to
> restore them
> > > > > from a fresh backup made on new master. This particular
> behavior stopped
> > > > me
> > > > > from implementing Master/Slave functionality in pgsql RA so far.
> > > > >
> > > > > BTW, why pgsql is set to is-managed="false" in your
configuration.With
> > > > this
> > > > > setting cluster will keep monitoring it but won't take any
> other actions
> > > > > AFAIK.
> > > >
> > > > Demote? Well, seeing as neither promote nor demote actually
> worked for me,
> > > > I thought I would start small.
> > > >
> > >
> > > It doesn't work because you have it in unmanaged state I think.
> > >
> >
> > I'm using the ocf-tester utility to test the agent. Won't there be
> a conflict if I try and have the cluster manage the resources and
> then try and wrest it's control away with my own testing agent?
> >
> >
> > >
> > > >
> > > > As far as the trigger file switching goes, you're of course
completely
> > > > right. This behavior isn't really a big deal in my environment, as
it's
> > > > meant as more of test and we want to bring back the demoted
servers up
> > > > manually, but I can see that it would cause a lot of problems in a
more
> > >
> > >
> > > That means that demote operation should stop master server
whichisn't the
> > > best behavior IMHO.
> > >
> >
> > I don't disagree. This was the policy that was "agreed" upon, so
> it's more of a political issue, really.
> >
> > Would you prefer putting it into RO mode?
> >
> > >
> > >
> > > > complex environment. When I tested the failover functionality
without
> > > > pacemaker, I have to perform a fresh backup even if I waited
> less than 30s
> > > > to bring the old master back up as a standby.
> > > >
> > > > I guess that with 9.1 this will be easier...
> > > >
> > > > I unmanaged the resources so that my test agent would handle
> them. Is this
> > > > incorrect?
> > > >
> > >
> > > Again I think you are wrong. In this mode pacemaker won't call your
RA to
> > > promote/demote or failover your resource.
> > >
> > >
> > > >
> > > >
> > > > >
> > > > >
> > > > > ?amon
> > > > > >
> > > > > >
> > > > > >
> > > > > > >> Unfortunately, promote/demote doesn't work. ocf-tester
> tries to use
> > > > the
> > > > > > >> "crm_attribute -N pgsql1 -n master-pgrql-replication-
> agent -l reboot
> > > > -v
> > > > > > >> 100", but the (unmanaged) resources don't accept the
> score change.
> > > > > > >>
> > > > > > >> I'm pretty sure that I just need to be hit with a clue
stick and
> > > > would
> > > > > > be
> > > > > > >> grateful for any help.
> > > > > > >>
> > > > > > >> Thanks,
> > > > > > >>
> > > > > > >> ?amon
> > > > > > >>
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Serge Dubrouski.
> > > > > > _______________________________________________
> > > > > > Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
> > > > > > http://oss.clusterlabs.org/mailman/listinfo/pacemaker
> > > > > >
> > > > > > Project Home: http://www.clusterlabs.org
> > > > > > Getting started:
> > > > http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
> > > > > > Bugs:
> > > > > >
> > > > http://developerbugs.linux-foundation.org/enter_bug.cgi?
> product=Pacemaker
> > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > > --
> > > > > Serge Dubrouski.
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> > > > http://oss.clusterlabs.org/mailman/listinfo/pacemaker
> > > >
> > > > Project Home: http://www.clusterlabs.org
> > > > Getting started:
http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
> > > > Bugs:
> > > > http://developerbugs.linux-foundation.org/enter_bug.cgi?
> product=Pacemaker
> > > >
> > > >
> > >
> > >
> > > --
> > > Serge Dubrouski.
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> >
> > Project Home: http://www.clusterlabs.org
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> > Bugs: http://developerbugs.linux-foundation.org/enter_bug.cgi?
> product=Pacemaker
>
> Daniel Bozeman
> American Roamer
> Systems Administrator
> daniel.bozeman at americanroamer.com
>
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