7.4. Configurare il cluster per DRBD

Un comoda funzione della shell crm è quella di rendere interattivi comandi per effettuare diversi cambiamenti automatici.

Inizialmente va lanciata la shell. Il prompt cambierà, indicando l'accesso alla modalità interattiva.

# crm cib
crm(live) #

Next we must create a working copy of the current configuration. This is where all our changes will go. The cluster will not see any of them until we say it’s ok. Notice again how the prompt changes, this time to indicate that we’re no longer looking at the live cluster.

cib crm(live) # cib new drbd
INFO: drbd shadow CIB created
crm(drbd) #

Ora è possibile creare il clone DRBD e visualizzare la configurazione revisionata.

crm(drbd) # configure primitive WebData ocf:linbit:drbd params drbd_resource=wwwdata \
    op monitor interval=60s
crm(drbd) # configure ms WebDataClone WebData meta master-max=1 master-node-max=1 \
    clone-max=2 clone-node-max=1 notify=truecrm(drbd) # configure shownode pcmk-1
node pcmk-2primitive WebData ocf:linbit:drbd \
 params drbd_resource="wwwdata" \
 op monitor interval="60s"primitive WebSite ocf:heartbeat:apache \
    params configfile="/etc/httpd/conf/httpd.conf" \
    op monitor interval="1min"
primitive ClusterIP ocf:heartbeat:IPaddr2 \
    params ip="192.168.122.101" cidr_netmask="32" \
    op monitor interval="30s"ms WebDataClone WebData \
 meta master-max="1" master-node-max="1" clone-max="2" clone-node-max="1" notify="true"
location prefer-pcmk-1 WebSite 50: pcmk-1
colocation website-with-ip inf: WebSite ClusterIP
order apache-after-ip inf: ClusterIP WebSite
property $id="cib-bootstrap-options" \
    dc-version="1.1.5-bdd89e69ba545404d02445be1f3d72e6a203ba2f" \
    cluster-infrastructure="openais" \
    expected-quorum-votes="2" \
    stonith-enabled="false" \
    no-quorum-policy="ignore"
rsc_defaults $id="rsc-options" \
    resource-stickiness="100"

Quando i cambiamenti saranno giudicati sufficienti sarà possibile indicare al cluster di iniziare ad usarli, ed utilizzare crm_mon per verificare che tutto stia funzionando.

crm(drbd) # cib commit drbdINFO: commited 'drbd' shadow CIB to the cluster
crm(drbd) # quitbye
# crm_mon
============
Last updated: Tue Sep 1 09:37:13 2009
Stack: openais
Current DC: pcmk-1 - partition with quorum
Version: 1.1.5-bdd89e69ba545404d02445be1f3d72e6a203ba2f
2 Nodes configured, 2 expected votes
3 Resources configured.
============

Online: [ pcmk-1 pcmk-2 ]

ClusterIP    (ocf::heartbeat:IPaddr):    Started pcmk-1
WebSite (ocf::heartbeat:apache):    Started pcmk-1Master/Slave Set: WebDataClone Masters: [ pcmk-2 ] Slaves: [ pcmk-1 ]

Nota

Dettagli su come aggiungere una seconda risorsa DRBD

Ora che DRBD sta funzionando è possibile configurare una risorsa filesystem per utilizzarlo. In aggiunta alla definizione del filesystem si necessita inoltre di indicare al cluster dove questa sia localizzata (cioè solo sul nodo Primary di DRBD) e quando ad essa è consentito avviarsi (solo dopo che il nodo Primary è stato attivato).

Ancora una volta verrà utilizzata la shell in modalità interattiva

# crm
crm(live) # cib new fs
INFO: fs shadow CIB created
crm(fs) # configure primitive WebFS ocf:heartbeat:Filesystem \
    params device="/dev/drbd/by-res/wwwdata" directory="/var/www/html" fstype="ext4"
crm(fs) # configure colocation fs_on_drbd inf: WebFS WebDataClone:Master
crm(fs) # configure order WebFS-after-WebData inf: WebDataClone:promote WebFS:start

We also need to tell the cluster that Apache needs to run on the same
machine as the filesystem and that it must be active before Apache can
start.

crm(fs) # configure colocation WebSite-with-WebFS inf: WebSite WebFS
crm(fs) # configure order WebSite-after-WebFS inf: WebFS WebSite

E' tempo di revisionare la configurazione aggiornata:

crm(fs) # crm configure show
node pcmk-1
node pcmk-2
primitive WebData ocf:linbit:drbd \
    params drbd_resource="wwwdata" \
    op monitor interval="60s"
primitive WebFS ocf:heartbeat:Filesystem \
    params device="/dev/drbd/by-res/wwwdata" directory="/var/www/html" fstype="ext4"
primitive WebSite ocf:heartbeat:apache \
    params configfile="/etc/httpd/conf/httpd.conf" \
    op monitor interval="1min"
primitive ClusterIP ocf:heartbeat:IPaddr2 \
    params ip="192.168.122.101" cidr_netmask="32" \
    op monitor interval="30s"
ms WebDataClone WebData \
    meta master-max="1" master-node-max="1" clone-max="2" clone-node-max="1" notify="true"
location prefer-pcmk-1 WebSite 50: pcmk-1
colocation WebSite-with-WebFS inf: WebSite WebFS
colocation fs_on_drbd inf: WebFS WebDataClone:Master
colocation website-with-ip inf: WebSite ClusterIP
order WebFS-after-WebData inf: WebDataClone:promote WebFS:start
order WebSite-after-WebFS inf: WebFS WebSite
order apache-after-ip inf: ClusterIP WebSite
property $id="cib-bootstrap-options" \
    dc-version="1.1.5-bdd89e69ba545404d02445be1f3d72e6a203ba2f" \
    cluster-infrastructure="openais" \
    expected-quorum-votes="2" \
    stonith-enabled="false" \
    no-quorum-policy="ignore"
rsc_defaults $id="rsc-options" \
    resource-stickiness="100"

Dopo la revisione della nuova configurazione questa va caricata e si potrà osservarla in azione all'interno del cluster.

crm(fs) # cib commit fs
INFO: commited 'fs' shadow CIB to the cluster
crm(fs) # quit
bye
# crm_mon
============
Last updated: Tue Sep 1 10:08:44 2009
Stack: openais
Current DC: pcmk-1 - partition with quorum
Version: 1.1.5-bdd89e69ba545404d02445be1f3d72e6a203ba2f
2 Nodes configured, 2 expected votes
4 Resources configured.
============

Online: [ pcmk-1 pcmk-2 ]

ClusterIP    (ocf::heartbeat:IPaddr):    Started pcmk-1
WebSite (ocf::heartbeat:apache): Started pcmk-1
Master/Slave Set: WebDataClone
    Masters: [ pcmk-1 ]
    Slaves: [ pcmk-2 ]
WebFS (ocf::heartbeat:Filesystem): Started pcmk-1

7.4.1. Testare la migrazione

We could shut down the active node again, but another way to safely simulate recovery is to put the node into what is called "standby mode". Nodes in this state tell the cluster that they are not allowed to run resources. Any resources found active there will be moved elsewhere. This feature can be particularly useful when updating the resources' packages.

Mettendo il nodo locale in standby consentirà di osservare il cluster spostare tutte le risorse sull'altro nodo. Da notare inoltre come lo stato del nodo cambierà, indicando che non può più ospitare risorse.

# crm node standby
# crm_mon
============
Last updated: Tue Sep 1 10:09:57 2009
Stack: openais
Current DC: pcmk-1 - partition with quorum
Version: 1.1.5-bdd89e69ba545404d02445be1f3d72e6a203ba2f
2 Nodes configured, 2 expected votes
4 Resources configured.
============
Node pcmk-1: standbyOnline: [ pcmk-2 ]

ClusterIP    (ocf::heartbeat:IPaddr):    Started pcmk-2
WebSite (ocf::heartbeat:apache):    Started pcmk-2
Master/Slave Set: WebDataClone
    Masters: [ pcmk-2 ]    Stopped: [ WebData:1 ]
WebFS  (ocf::heartbeat:Filesystem):  Started pcmk-2

Fatto quanto necessario su pcmk-1 (in questo caso nulla, si è solo osservato le risorse spostarsi), è possibile consentire il nodo ad essere nuovamente parte integrante del cluster.

# crm node online
# crm_mon
============
Last updated: Tue Sep 1 10:13:25 2009
Stack: openais
Current DC: pcmk-1 - partition with quorum
Version: 1.1.5-bdd89e69ba545404d02445be1f3d72e6a203ba2f
2 Nodes configured, 2 expected votes
4 Resources configured.
============
Online: [ pcmk-1 pcmk-2 ]
ClusterIP    (ocf::heartbeat:IPaddr):    Started pcmk-2
WebSite (ocf::heartbeat:apache):    Started pcmk-2
Master/Slave Set: WebDataClone
    Masters: [ pcmk-2 ]
    Slaves: [ pcmk-1 ]
WebFS  (ocf::heartbeat:Filesystem):  Started pcmk-2

Notare come ora l'impostazione di stickiness delle risorse prevenga la migrazione dei servizi nuovamente verso pcmk-1.