10. Configuration Recap

10.1. Final Cluster Configuration

[root@pcmk-1 ~]# pcs resource
  * ClusterIP       (ocf:heartbeat:IPaddr2):         Started pcmk-1
  * WebSite (ocf:heartbeat:apache):  Started pcmk-1
  * Clone Set: WebData-clone [WebData] (promotable):
    * Promoted: [ pcmk-1 pcmk-2 ]
  * Clone Set: dlm-clone [dlm]:
    * Started: [ pcmk-1 pcmk-2 ]
  * Clone Set: WebFS-clone [WebFS]:
    * Started: [ pcmk-1 pcmk-2 ]

[root@pcmk-1 ~]# pcs resource op defaults
Meta Attrs: op_defaults-meta_attributes
  timeout=240s

[root@pcmk-1 ~]# pcs stonith
  * fence_dev       (stonith:some_fence_agent):      Started pcmk-1

[root@pcmk-1 ~]# pcs constraint
Location Constraints:
  Resource: WebSite
    Enabled on:
      Node: pcmk-2 (score:50)
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory)
  promote WebData-clone then start WebFS-clone (kind:Mandatory)
  start WebFS-clone then start WebSite (kind:Mandatory)
  start dlm-clone then start WebFS-clone (kind:Mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY)
  WebFS-clone with WebData-clone (score:INFINITY) (rsc-role:Started) (with-rsc-role:Promoted)
  WebSite with WebFS-clone (score:INFINITY)
  WebFS-clone with dlm-clone (score:INFINITY)
Ticket Constraints:

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Cluster Summary:
  * Stack: corosync
  * Current DC: pcmk-1 (version 2.1.2-4.el9-ada5c3b36e2) - partition with quorum
  * Last updated: Wed Jul 27 08:57:57 2022
  * Last change:  Wed Jul 27 08:55:00 2022 by root via cibadmin on pcmk-1
  * 2 nodes configured
  * 9 resource instances configured

Node List:
  * Online: [ pcmk-1 pcmk-2 ]

Full List of Resources:
  * fence_dev       (stonith:some_fence_agent):      Started pcmk-1
  * ClusterIP       (ocf:heartbeat:IPaddr2):         Started pcmk-1
  * WebSite (ocf:heartbeat:apache):  Started pcmk-1
  * Clone Set: WebData-clone [WebData] (promotable):
    * Promoted: [ pcmk-1 pcmk-2 ]
  * Clone Set: dlm-clone [dlm]:
    * Started: [ pcmk-1 pcmk-2 ]
  * Clone Set: WebFS-clone [WebFS]:
    * Started: [ pcmk-1 pcmk-2 ]

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

[root@pcmk-1 ~]# pcs config
Cluster Name: mycluster
Corosync Nodes:
 pcmk-1 pcmk-2
Pacemaker Nodes:
 pcmk-1 pcmk-2

Resources:
 Resource: ClusterIP (class=ocf provider=heartbeat type=IPaddr2)
  Attributes: cidr_netmask=24 ip=192.168.122.120
  Operations: monitor interval=30s (ClusterIP-monitor-interval-30s)
              start interval=0s timeout=20s (ClusterIP-start-interval-0s)
              stop interval=0s timeout=20s (ClusterIP-stop-interval-0s)
 Resource: WebSite (class=ocf provider=heartbeat type=apache)
  Attributes: configfile=/etc/httpd/conf/httpd.conf statusurl=http://localhost/server-status
  Operations: monitor interval=1min (WebSite-monitor-interval-1min)
              start interval=0s timeout=40s (WebSite-start-interval-0s)
              stop interval=0s timeout=60s (WebSite-stop-interval-0s)
 Clone: WebData-clone
  Meta Attrs: clone-max=2 clone-node-max=1 notify=true promotable=true promoted-max=2 promoted-node-max=1
  Resource: WebData (class=ocf provider=linbit type=drbd)
   Attributes: drbd_resource=wwwdata
   Operations: demote interval=0s timeout=90 (WebData-demote-interval-0s)
               monitor interval=29s role=Promoted (WebData-monitor-interval-29s)
               monitor interval=31s role=Unpromoted (WebData-monitor-interval-31s)
               notify interval=0s timeout=90 (WebData-notify-interval-0s)
               promote interval=0s timeout=90 (WebData-promote-interval-0s)
               reload interval=0s timeout=30 (WebData-reload-interval-0s)
               start interval=0s timeout=240 (WebData-start-interval-0s)
               stop interval=0s timeout=100 (WebData-stop-interval-0s)
 Clone: dlm-clone
  Meta Attrs: interleave=true ordered=true
  Resource: dlm (class=ocf provider=pacemaker type=controld)
   Operations: monitor interval=60s (dlm-monitor-interval-60s)
               start interval=0s timeout=90s (dlm-start-interval-0s)
               stop interval=0s timeout=100s (dlm-stop-interval-0s)
 Clone: WebFS-clone
  Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
   Attributes: device=/dev/drbd1 directory=/var/www/html fstype=gfs2
   Operations: monitor interval=20s timeout=40s (WebFS-monitor-interval-20s)
               start interval=0s timeout=60s (WebFS-start-interval-0s)
               stop interval=0s timeout=60s (WebFS-stop-interval-0s)

Stonith Devices:
 Resource: fence_dev (class=stonith type=some_fence_agent)
  Attributes: pcmk_delay_base=pcmk-1:5s;pcmk-2:0s pcmk_host_map=pcmk-1:almalinux9-1;pcmk-2:almalinux9-2
  Operations: monitor interval=60s (fence_dev-monitor-interval-60s)
Fencing Levels:

Location Constraints:
  Resource: WebSite
    Enabled on:
      Node: pcmk-2 (score:50) (id:location-WebSite-pcmk-2-50)
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory) (id:order-ClusterIP-WebSite-mandatory)
  promote WebData-clone then start WebFS-clone (kind:Mandatory) (id:order-WebData-clone-WebFS-mandatory)
  start WebFS-clone then start WebSite (kind:Mandatory) (id:order-WebFS-WebSite-mandatory)
  start dlm-clone then start WebFS-clone (kind:Mandatory) (id:order-dlm-clone-WebFS-mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY) (id:colocation-WebSite-ClusterIP-INFINITY)
  WebFS-clone with WebData-clone (score:INFINITY) (rsc-role:Started) (with-rsc-role:Promoted) (id:colocation-WebFS-WebData-clone-INFINITY)
  WebSite with WebFS-clone (score:INFINITY) (id:colocation-WebSite-WebFS-INFINITY)
  WebFS-clone with dlm-clone (score:INFINITY) (id:colocation-WebFS-dlm-clone-INFINITY)
Ticket Constraints:

Alerts:
 No alerts defined

Resources Defaults:
  Meta Attrs: build-resource-defaults
    resource-stickiness=100
Operations Defaults:
  Meta Attrs: op_defaults-meta_attributes
    timeout=240s

Cluster Properties:
 cluster-infrastructure: corosync
 cluster-name: mycluster
 dc-version: 2.1.2-4.el9-ada5c3b36e2
 have-watchdog: false
 last-lrm-refresh: 1658896047
 no-quorum-policy: freeze
 stonith-enabled: true

Tags:
 No tags defined

Quorum:
  Options:

10.2. Node List

[root@pcmk-1 ~]# pcs status nodes
Pacemaker Nodes:
 Online: pcmk-1 pcmk-2
 Standby:
 Standby with resource(s) running:
 Maintenance:
 Offline:
Pacemaker Remote Nodes:
 Online:
 Standby:
 Standby with resource(s) running:
 Maintenance:
 Offline:

10.3. Cluster Options

[root@pcmk-1 ~]# pcs property
Cluster Properties:
 cluster-infrastructure: corosync
 cluster-name: mycluster
 dc-version: 2.1.2-4.el9-ada5c3b36e2
 have-watchdog: false
 no-quorum-policy: freeze
 stonith-enabled: true

The output shows cluster-wide configuration options, as well as some baseline- level state information. The output includes:

  • cluster-infrastructure - the cluster communications layer in use
  • cluster-name - the cluster name chosen by the administrator when the cluster was created
  • dc-version - the version (including upstream source-code hash) of pacemaker used on the Designated Controller, which is the node elected to determine what actions are needed when events occur
  • have-watchdog - whether watchdog integration is enabled; set automatically when SBD is enabled
  • stonith-enabled - whether nodes may be fenced as part of recovery

Note

This command is equivalent to pcs property config.

10.4. Resources

10.4.1. Default Options

[root@pcmk-1 ~]# pcs resource defaults
Meta Attrs: build-resource-defaults
  resource-stickiness=100

This shows cluster option defaults that apply to every resource that does not explicitly set the option itself. Above:

  • resource-stickiness - Specify how strongly a resource prefers to remain on its current node. Alternatively, you can view this as the level of aversion to moving healthy resources to other machines.

10.4.2. Fencing

[root@pcmk-1 ~]# pcs stonith status
  * fence_dev       (stonith:some_fence_agent):      Started pcmk-1
[root@pcmk-1 ~]# pcs stonith config
 Resource: fence_dev (class=stonith type=some_fence_agent)
  Attributes: pcmk_delay_base=pcmk-1:5s;pcmk-2:0s pcmk_host_map=pcmk-1:almalinux9-1;pcmk-2:almalinux9-2
  Operations: monitor interval=60s (fence_dev-monitor-interval-60s)

10.4.3. Service Address

Users of the services provided by the cluster require an unchanging address with which to access it.

[root@pcmk-1 ~]# pcs resource config ClusterIP
 Resource: ClusterIP (class=ocf provider=heartbeat type=IPaddr2)
  Attributes: cidr_netmask=24 ip=192.168.122.120
  Operations: monitor interval=30s (ClusterIP-monitor-interval-30s)
              start interval=0s timeout=20s (ClusterIP-start-interval-0s)
              stop interval=0s timeout=20s (ClusterIP-stop-interval-0s)

10.4.4. DRBD - Shared Storage

Here, we define the DRBD service and specify which DRBD resource (from /etc/drbd.d/\*.res) it should manage. We make it a promotable clone resource and, in order to have an active/active setup, allow both instances to be promoted at the same time. We also set the notify option so that the cluster will tell the drbd agent when its peer changes state.

[root@pcmk-1 ~]# pcs resource config WebData-clone
 Clone: WebData-clone
  Meta Attrs: clone-max=2 clone-node-max=1 notify=true promotable=true promoted-max=2 promoted-node-max=1
  Resource: WebData (class=ocf provider=linbit type=drbd)
   Attributes: drbd_resource=wwwdata
   Operations: demote interval=0s timeout=90 (WebData-demote-interval-0s)
               monitor interval=29s role=Promoted (WebData-monitor-interval-29s)
               monitor interval=31s role=Unpromoted (WebData-monitor-interval-31s)
               notify interval=0s timeout=90 (WebData-notify-interval-0s)
               promote interval=0s timeout=90 (WebData-promote-interval-0s)
               reload interval=0s timeout=30 (WebData-reload-interval-0s)
               start interval=0s timeout=240 (WebData-start-interval-0s)
               stop interval=0s timeout=100 (WebData-stop-interval-0s)
[root@pcmk-1 ~]# pcs constraint ref WebData-clone
Resource: WebData-clone
  colocation-WebFS-WebData-clone-INFINITY
  order-WebData-clone-WebFS-mandatory

10.4.5. Cluster Filesystem

The cluster filesystem ensures that files are read and written correctly. We need to specify the block device (provided by DRBD), where we want it mounted and that we are using GFS2. Again, it is a clone because it is intended to be active on both nodes. The additional constraints ensure that it can only be started on nodes with active DLM and DRBD instances.

[root@pcmk-1 ~]# pcs resource config WebFS-clone
 Clone: WebFS-clone
  Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
   Attributes: device=/dev/drbd1 directory=/var/www/html fstype=gfs2
   Operations: monitor interval=20s timeout=40s (WebFS-monitor-interval-20s)
               start interval=0s timeout=60s (WebFS-start-interval-0s)
               stop interval=0s timeout=60s (WebFS-stop-interval-0s)
[root@pcmk-1 ~]# pcs constraint ref WebFS-clone
Resource: WebFS-clone
  colocation-WebFS-WebData-clone-INFINITY
  colocation-WebSite-WebFS-INFINITY
  colocation-WebFS-dlm-clone-INFINITY
  order-WebData-clone-WebFS-mandatory
  order-WebFS-WebSite-mandatory
  order-dlm-clone-WebFS-mandatory

10.4.6. Apache

Lastly, we have the actual service, Apache. We need only tell the cluster where to find its main configuration file and restrict it to running on a node that has the required filesystem mounted and the IP address active.

[root@pcmk-1 ~]# pcs resource config WebSite
 Resource: WebSite (class=ocf provider=heartbeat type=apache)
  Attributes: configfile=/etc/httpd/conf/httpd.conf statusurl=http://localhost/server-status
  Operations: monitor interval=1min (WebSite-monitor-interval-1min)
              start interval=0s timeout=40s (WebSite-start-interval-0s)
              stop interval=0s timeout=60s (WebSite-stop-interval-0s)
[root@pcmk-1 ~]# pcs constraint ref WebSite
Resource: WebSite
  colocation-WebSite-ClusterIP-INFINITY
  colocation-WebSite-WebFS-INFINITY
  location-WebSite-pcmk-2-50
  order-ClusterIP-WebSite-mandatory
  order-WebFS-WebSite-mandatory