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Chapter 54. Configuring cluster resources
Create and delete cluster resources with the following commands.
The format for the command to create a cluster resource is as follows:
pcs resource create resource_id [standard:[provider:]]type [resource_options] [op operation_action operation_options [operation_action operation options]...] [meta meta_options...] [clone [clone_options] | master [master_options] [--wait[=n]]
Key cluster resource creation options include the following:
-
The
--before
and--after
options specify the position of the added resource relative to a resource that already exists in a resource group. -
Specifying the
--disabled
option indicates that the resource is not started automatically.
There is no limit to the number of resources you can create in a cluster.
You can determine the behavior of a resource in a cluster by configuring constraints for that resource.
Resource creation examples
The following command creates a resource with the name VirtualIP
of standard ocf
, provider heartbeat
, and type IPaddr2
. The floating address of this resource is 192.168.0.120, and the system will check whether the resource is running every 30 seconds.
# pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.120 cidr_netmask=24 op monitor interval=30s
Alternately, you can omit the standard and provider fields and use the following command. This will default to a standard of ocf
and a provider of heartbeat
.
# pcs resource create VirtualIP IPaddr2 ip=192.168.0.120 cidr_netmask=24 op monitor interval=30s
Deleting a configured resource
Delete a configured resource with the following command.
pcs resource delete resource_id
For example, the following command deletes an existing resource with a resource ID of VirtualIP
.
# pcs resource delete VirtualIP
54.1. Resource agent identifiers
The identifiers that you define for a resource tell the cluster which agent to use for the resource, where to find that agent and what standards it conforms to.
The following table describes these properties of a resource agent.
Field | Description |
---|---|
standard | The standard the agent conforms to. Allowed values and their meaning:
*
*
*
*
* |
type |
The name of the resource agent you wish to use, for example |
provider |
The OCF spec allows multiple vendors to supply the same resource agent. Most of the agents shipped by Red Hat use |
The following table summarizes the commands that display the available resource properties.
pcs Display Command | Output |
---|---|
| Displays a list of all available resources. |
| Displays a list of available resource agent standards. |
| Displays a list of available resource agent providers. |
| Displays a list of available resources filtered by the specified string. You can use this command to display resources filtered by the name of a standard, a provider, or a type. |
54.2. Displaying resource-specific parameters
For any individual resource, you can use the following command to display a description of the resource, the parameters you can set for that resource, and the default values that are set for the resource.
pcs resource describe [standard:[provider:]]type
For example, the following command displays information for a resource of type apache
.
# pcs resource describe ocf:heartbeat:apache
This is the resource agent for the Apache Web server.
This resource agent operates both version 1.x and version 2.x Apache
servers.
...
54.3. Configuring resource meta options
In addition to the resource-specific parameters, you can configure additional resource options for any resource. These options are used by the cluster to decide how your resource should behave.
The following table describes the resource meta options.
Field | Default | Description |
---|---|---|
|
| If not all resources can be active, the cluster will stop lower priority resources in order to keep higher priority ones active. |
|
| Indicates what state the cluster should attempt to keep this resource in. Allowed values:
*
*
*
*
As of RHEL 8.5, The |
|
|
Indicates whether the cluster is allowed to start and stop the resource. Allowed values: |
| 0 | Value to indicate how much the resource prefers to stay where it is. For information on this attribute, see Configuring a resource to prefer its current node. |
| Calculated | Indicates under what conditions the resource can be started.
Defaults to
*
*
*
* |
|
|
How many failures may occur for this resource on a node before this node is marked ineligible to host this resource. A value of 0 indicates that this feature is disabled (the node will never be marked ineligible); by contrast, the cluster treats |
|
|
Used in conjunction with the |
|
| Indicates what the cluster should do if it ever finds the resource active on more than one node. Allowed values:
*
*
*
* |
|
|
(RHEL 8.4 and later) Sets the default value for the |
|
|
(RHEL 8.7 and later) When set to |
54.3.1. Changing the default value of a resource option
As of Red Hat Enterprise Linux 8.3, you can change the default value of a resource option for all resources with the pcs resource defaults update
command. The following command resets the default value of resource-stickiness
to 100.
# pcs resource defaults update resource-stickiness=100
The original pcs resource defaults name=value
command, which set defaults for all resources in previous releases, remains supported unless there is more than one set of defaults configured. However, pcs resource defaults update
is now the preferred version of the command.
54.3.2. Changing the default value of a resource option for sets of resources
As of Red Hat Enterprise Linux 8.3, you can create multiple sets of resource defaults with the pcs resource defaults set create
command, which allows you to specify a rule that contains resource
expressions. In RHEL 8.3, only resource
expressions, including and
, or
and parentheses, are allowed in rules that you specify with this command. In RHEL 8.4 and later, only resource
and date
expressions, including and
, or
and parentheses, are allowed in rules that you specify with this command.
With the pcs resource defaults set create
command, you can configure a default resource value for all resources of a particular type. If, for example, you are running databases which take a long time to stop, you can increase the resource-stickiness
default value for all resources of the database type to prevent those resources from moving to other nodes more often than you desire.
The following command sets the default value of resource-stickiness
to 100 for all resources of type pqsql
.
-
The
id
option, which names the set of resource defaults, is not mandatory. If you do not set this optionpcs
will generate an ID automatically. Setting this value allows you to provide a more descriptive name. In this example,
::pgsql
means a resource of any class, any provider, of typepgsql
.-
Specifying
ocf:heartbeat:pgsql
would indicate classocf
, providerheartbeat
, typepgsql
, -
Specifying
ocf:pacemaker:
would indicate all resources of classocf
, providerpacemaker
, of any type.
-
Specifying
# pcs resource defaults set create id=pgsql-stickiness meta resource-stickiness=100 rule resource ::pgsql
To change the default values in an existing set, use the pcs resource defaults set update
command.
54.3.3. Displaying currently configured resource defaults
The pcs resource defaults
command displays a list of currently configured default values for resource options, including any rules you specified.
The following example shows the output of this command after you have reset the default value of resource-stickiness
to 100.
# pcs resource defaults
Meta Attrs: rsc_defaults-meta_attributes
resource-stickiness=100
The following example shows the output of this command after you have reset the default value of resource-stickiness
to 100 for all resources of type pqsql
and set the id
option to id=pgsql-stickiness
.
# pcs resource defaults
Meta Attrs: pgsql-stickiness
resource-stickiness=100
Rule: boolean-op=and score=INFINITY
Expression: resource ::pgsql
54.3.4. Setting meta options on resource creation
Whether you have reset the default value of a resource meta option or not, you can set a resource option for a particular resource to a value other than the default when you create the resource. The following shows the format of the pcs resource create
command you use when specifying a value for a resource meta option.
pcs resource create resource_id [standard:[provider:]]type [resource options] [meta meta_options...]
For example, the following command creates a resource with a resource-stickiness
value of 50.
# pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.120 meta resource-stickiness=50
You can also set the value of a resource meta option for an existing resource, group, or cloned resource with the following command.
pcs resource meta resource_id | group_id | clone_id meta_options
In the following example, there is an existing resource named dummy_resource
. This command sets the failure-timeout
meta option to 20 seconds, so that the resource can attempt to restart on the same node in 20 seconds.
# pcs resource meta dummy_resource failure-timeout=20s
After executing this command, you can display the values for the resource to verify that failure-timeout=20s
is set.
# pcs resource config dummy_resource
Resource: dummy_resource (class=ocf provider=heartbeat type=Dummy)
Meta Attrs: failure-timeout=20s
...
54.4. Configuring resource groups
One of the most common elements of a cluster is a set of resources that need to be located together, start sequentially, and stop in the reverse order. To simplify this configuration, Pacemaker supports the concept of resource groups.
54.4.1. Creating a resource group
You create a resource group with the following command, specifying the resources to include in the group. If the group does not exist, this command creates the group. If the group exists, this command adds additional resources to the group. The resources will start in the order you specify them with this command, and will stop in the reverse order of their starting order.
pcs resource group add group_name resource_id [resource_id] ... [resource_id] [--before resource_id | --after resource_id]
You can use the --before
and --after
options of this command to specify the position of the added resources relative to a resource that already exists in the group.
You can also add a new resource to an existing group when you create the resource, using the following command. The resource you create is added to the group named group_name. If the group group_name does not exist, it will be created.
pcs resource create resource_id [standard:[provider:]]type [resource_options] [op operation_action operation_options] --group group_name
There is no limit to the number of resources a group can contain. The fundamental properties of a group are as follows.
- Resources are colocated within a group.
- Resources are started in the order in which you specify them. If a resource in the group cannot run anywhere, then no resource specified after that resource is allowed to run.
- Resources are stopped in the reverse order in which you specify them.
The following example creates a resource group named shortcut
that contains the existing resources IPaddr
and Email
.
# pcs resource group add shortcut IPaddr Email
In this example:
-
The
IPaddr
is started first, thenEmail
. -
The
Email
resource is stopped first, thenIPAddr
. -
If
IPaddr
cannot run anywhere, neither canEmail
. -
If
Email
cannot run anywhere, however, this does not affectIPaddr
in any way.
54.4.2. Removing a resource group
You remove a resource from a group with the following command. If there are no remaining resources in the group, this command removes the group itself.
pcs resource group remove group_name resource_id...
54.4.3. Displaying resource groups
The following command lists all currently configured resource groups.
pcs resource group list
54.4.4. Group options
You can set the following options for a resource group, and they maintain the same meaning as when they are set for a single resource: priority
, target-role
, is-managed
. For information on resource meta options, see Configuring resource meta options.
54.4.5. Group stickiness
Stickiness, the measure of how much a resource wants to stay where it is, is additive in groups. Every active resource of the group will contribute its stickiness value to the group’s total. So if the default resource-stickiness
is 100, and a group has seven members, five of which are active, then the group as a whole will prefer its current location with a score of 500.
54.5. Determining resource behavior
You can determine the behavior of a resource in a cluster by configuring constraints for that resource. You can configure the following categories of constraints:
-
location
constraints — A location constraint determines which nodes a resource can run on. For information on configuring location constraints, see Determining which nodes a resource can run on. -
order
constraints — An ordering constraint determines the order in which the resources run. For information on configuring ordering constraints, see Determining the order in which cluster resources are run. -
colocation
constraints — A colocation constraint determines where resources will be placed relative to other resources. For information on colocation constraints, see Colocating cluster resources.
As a shorthand for configuring a set of constraints that will locate a set of resources together and ensure that the resources start sequentially and stop in reverse order, Pacemaker supports the concept of resource groups. After you have created a resource group, you can configure constraints on the group itself just as you configure constraints for individual resources.