5. Cluster Resources

5.1. What is a Cluster Resource?

A resource is a service managed by Pacemaker. The simplest type of resource, a primitive, is described in this chapter. More complex forms, such as groups and clones, are described in later chapters.

Every primitive has a resource agent that provides Pacemaker a standardized interface for managing the service. This allows Pacemaker to be agnostic about the services it manages. Pacemaker doesn’t need to understand how the service works because it relies on the resource agent to do the right thing when asked.

Every resource has a standard (also called class) specifying the interface that its resource agent follows, and a type identifying the specific service being managed.

5.2. Resource Standards

Pacemaker can use resource agents complying with these standards, described in more detail below:

• ocf
• lsb
• systemd
• service
• stonith
• nagios (deprecated since 2.1.6)
• upstart (deprecated since 2.1.0)

Support for some standards is controlled by build options and so might not be available in any particular build of Pacemaker. The command crm_resource --list-standards will show which standards are supported by the local build.

5.2.1. Open Cluster Framework

The Open Cluster Framework (OCF) Resource Agent API is a ClusterLabs standard for managing services. It is the most preferred since it is specifically designed for use in a Pacemaker cluster.

OCF agents are scripts that support a variety of actions including start, stop, and monitor. They may accept parameters, making them more flexible than other standards. The number and purpose of parameters is left to the agent, which advertises them via the meta-data action.

Unlike other standards, OCF agents have a provider as well as a standard and type.

For more information, see the “Resource Agents” chapter of Pacemaker Administration and the OCF standard.

5.2.2. Systemd

Most Linux distributions use Systemd for system initialization and service management. Unit files specify how to manage services and are usually provided by the distribution.

Pacemaker can manage systemd services. Simply create a resource with systemd as the resource standard and the unit file name as the resource type. Do not run systemctl enable on the unit.

Important

Make sure that any systemd services to be controlled by the cluster are not enabled to start at boot.

5.2.3. Linux Standard Base

LSB resource agents, also known as SysV-style, are scripts that provide start, stop, and status actions for a service.

They are provided by some operating system distributions. If a full path is not given, they are assumed to be located in a directory specified when your Pacemaker software was built (usually /etc/init.d).

In order to be used with Pacemaker, they must conform to the LSB specification as it relates to init scripts.

Warning

Some LSB scripts do not fully comply with the standard. For details on how to check whether your script is LSB-compatible, see the “Resource Agents” chapter of Pacemaker Administration. Common problems include:

• Not implementing the status action
• Not observing the correct exit status codes
• Starting a started resource returns an error
• Stopping a stopped resource returns an error

Important

Make sure the host is not configured to start any LSB services at boot that will be controlled by the cluster.

5.2.4. System Services

Since there are various types of system services (systemd, upstart, and lsb), Pacemaker supports a special service alias which intelligently figures out which one applies to a given cluster node.

This is particularly useful when the cluster contains a mix of systemd, upstart, and lsb.

In order, Pacemaker will try to find the named service as:

• an LSB init script
• a Systemd unit file
• an Upstart job

5.2.5. STONITH

The stonith standard is used for managing fencing devices, discussed later in Fencing.

5.2.6. Nagios Plugins

Nagios Plugins are a way to monitor services. Pacemaker can use these as resources, to react to a change in the service’s status.

To use plugins as resources, Pacemaker must have been built with support, and OCF-style meta-data for the plugins must be installed on nodes that can run them. Meta-data for several common plugins is provided by the nagios-agents-metadata project.

The supported parameters for such a resource are same as the long options of the plugin.

Start and monitor actions for plugin resources are implemented as invoking the plugin. A plugin result of “OK” (0) is treated as success, a result of “WARN” (1) is treated as a successful but degraded service, and any other result is considered a failure.

A plugin resource is not going to change its status after recovery by restarting the plugin, so using them alone does not make sense with on-fail set (or left to default) to restart. Another value could make sense, for example, if you want to fence or standby nodes that cannot reach some external service.

A more common use case for plugin resources is to configure them with a container meta-attribute set to the name of another resource that actually makes the service available, such as a virtual machine or container.

With container set, the plugin resource will automatically be colocated with the containing resource and ordered after it, and the containing resource will be considered failed if the plugin resource fails. This allows monitoring of a service inside a virtual machine or container, with recovery of the virtual machine or container if the service fails.

Warning

Nagios support is deprecated in Pacemaker. Support will be dropped entirely at the next major release of Pacemaker.

For monitoring a service inside a virtual machine or container, the recommended alternative is to configure the virtual machine as a guest node or the container as a bundle. For other use cases, or when the virtual machine or container image cannot be modified, the recommended alternative is to write a custom OCF agent for the service (which may even call the Nagios plugin as part of its status action).

5.2.7. Upstart

Some Linux distributions previously used Upstart for system initialization and service management. Pacemaker is able to manage services using Upstart if the local system supports them and support was enabled when your Pacemaker software was built.

The jobs that specify how services are managed are usually provided by the operating system distribution.

Important

Make sure the host is not configured to start any Upstart services at boot that will be controlled by the cluster.

Warning

Upstart support is deprecated in Pacemaker. Upstart is no longer actively maintained, and test platforms for it are no longer readily usable. Support will be dropped entirely at the next major release of Pacemaker.

5.3. Resource Properties

These values tell the cluster which resource agent to use for the resource, where to find that resource agent and what standards it conforms to.

Properties of a Primitive Resource

Field	Description
id	Your name for the resource
class	The standard the resource agent conforms to. Allowed values: lsb, ocf, service, stonith, systemd, nagios (deprecated since 2.1.6), and upstart (deprecated since 2.1.0)
description	A description of the Resource Agent, intended for local use. E.g. IP address for website
type	The name of the Resource Agent you wish to use. E.g. IPaddr or Filesystem
provider	The OCF spec allows multiple vendors to supply the same resource agent. To use the OCF resource agents supplied by the Heartbeat project, you would specify heartbeat here.

The XML definition of a resource can be queried with the crm_resource tool. For example:

# crm_resource --resource Email --query-xml

might produce:

A system resource definition

<primitive id="Email" class="service" type="exim"/>

Note

One of the main drawbacks to system services (LSB, systemd or Upstart) resources is that they do not allow any parameters!

An OCF resource definition

<primitive id="Public-IP" class="ocf" type="IPaddr" provider="heartbeat">
   <instance_attributes id="Public-IP-params">
      <nvpair id="Public-IP-ip" name="ip" value="192.0.2.2"/>
   </instance_attributes>
</primitive>

5.4. Resource Options

Resources have two types of options: meta-attributes and instance attributes. Meta-attributes apply to any type of resource, while instance attributes are specific to each resource agent.

5.4.1. Resource Meta-Attributes

Meta-attributes are used by the cluster to decide how a resource should behave and can be easily set using the --meta option of the crm_resource command.

Meta-attributes of a Primitive Resource

Name	Type	Default	Description
priority	score	0	If not all resources can be active, the cluster will stop lower-priority resources in order to keep higher-priority ones active.
critical	boolean	true	Use this value as the default for influence in all colocation constraints involving this resource, as well as in the implicit colocation constraints created if this resource is in a group. For details, see Colocation Influence. (since 2.1.0)
target-role	enumeration	Started	What state should the cluster attempt to keep this resource in? Allowed values: Stopped: Force the resource to be stopped Started: Allow the resource to be started (and in the case of promotable clone resources, promoted if appropriate) Unpromoted: Allow the resource to be started, but only in the unpromoted role if the resource is promotable Promoted: Equivalent to Started
is-managed	boolean	true	If false, the cluster will not start, stop, promote, or demote the resource on any node. Recurring actions for the resource are unaffected. Maintenance mode overrides this setting.
maintenance	boolean	false	If true, the cluster will not start, stop, promote, or demote the resource on any node, and will pause any recurring monitors (except those specifying role as Stopped). If true, the maintenance-mode cluster option or maintenance node attribute overrides this.
resource-stickiness	score	1 for individual clone instances, 0 for all other resources	A score that will be added to the current node when a resource is already active. This allows running resources to stay where they are, even if they would be placed elsewhere if they were being started from a stopped state.
requires	enumeration	quorum for resources with a class of stonith, otherwise unfencing if unfencing is active in the cluster, otherwise fencing if stonith-enabled is true, otherwise quorum	Conditions under which the resource can be started. Allowed values: nothing: The cluster can always start this resource. quorum: The cluster can start this resource only if a majority of the configured nodes are active. fencing: The cluster can start this resource only if a majority of the configured nodes are active and any failed or unknown nodes have been fenced. unfencing: The cluster can only start this resource if a majority of the configured nodes are active and any failed or unknown nodes have been fenced and only on nodes that have been unfenced.
migration-threshold	score	INFINITY	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 INFINITY (the default) as a very large but finite number. This option has an effect only if the failed operation specifies on-fail as restart (the default), and additionally for failed start operations, if the cluster property start-failure-is-fatal is false.
failure-timeout	duration	0	Ignore previously failed resource actions after this much time has passed without new failures (potentially allowing the resource back to the node on which it failed, if it previously reached its migration-threshold there). A value of 0 indicates that failures do not expire. WARNING: If this value is low, and pending cluster activity prevents the cluster from responding to a failure within that time, then the failure will be ignored completely and will not cause recovery of the resource, even if a recurring action continues to report failure. It should be at least greater than the longest action timeout for all resources in the cluster. A value in hours or days is reasonable.
multiple-active	enumeration	stop_start	What should the cluster do if it ever finds the resource active on more than one node? Allowed values: block: mark the resource as unmanaged stop_only: stop all active instances and leave them that way stop_start: stop all active instances and start the resource in one location only stop_unexpected: stop all active instances except where the resource should be active (this should be used only when extra instances are not expected to disrupt existing instances, and the resource agent’s monitor of an existing instance is capable of detecting any problems that could be caused; note that any resources ordered after this will still need to be restarted) (since 2.1.3)
allow-migrate	boolean	true for ocf:pacemaker:remote resources, false otherwise	Whether the cluster should try to “live migrate” this resource when it needs to be moved (see Migrating Resources)
allow-unhealthy-nodes	boolean	false	Whether the resource should be able to run on a node even if the node’s health score would otherwise prevent it (see Tracking Node Health) (since 2.1.3)
container-attribute-target	enumeration		Specific to bundle resources; see Bundle Node Attributes
remote-node	text		The name of the Pacemaker Remote guest node this resource is associated with, if any. If specified, this both enables the resource as a guest node and defines the unique name used to identify the guest node. The guest must be configured to run the Pacemaker Remote daemon when it is started. WARNING: This value cannot overlap with any resource or node IDs.
remote-addr	text	value of remote-node	If remote-node is specified, the IP address or hostname used to connect to the guest via Pacemaker Remote. The Pacemaker Remote daemon on the guest must be configured to accept connections on this address.
remote-port	port	3121	If remote-node is specified, the port on the guest used for its Pacemaker Remote connection. The Pacemaker Remote daemon on the guest must be configured to listen on this port.
remote-connect-timeout	timeout	60s	If remote-node is specified, how long before a pending guest connection will time out.
remote-allow-migrate	boolean	true	If remote-node is specified, this acts as the allow-migrate meta-attribute for the implicit remote connection resource (ocf:pacemaker:remote).

As an example of setting resource options, if you performed the following commands on an LSB Email resource:

# crm_resource --meta --resource Email --set-parameter priority --parameter-value 100
# crm_resource -m -r Email -p multiple-active -v block

the resulting resource definition might be:

An LSB resource with cluster options

<primitive id="Email" class="lsb" type="exim">
  <meta_attributes id="Email-meta_attributes">
    <nvpair id="Email-meta_attributes-priority" name="priority" value="100"/>
    <nvpair id="Email-meta_attributes-multiple-active" name="multiple-active" value="block"/>
  </meta_attributes>
</primitive>

In addition to the cluster-defined meta-attributes described above, you may also configure arbitrary meta-attributes of your own choosing. Most commonly, this would be done for use in rules. For example, an IT department might define a custom meta-attribute to indicate which company department each resource is intended for. To reduce the chance of name collisions with cluster-defined meta-attributes added in the future, it is recommended to use a unique, organization-specific prefix for such attributes.

5.4.2. Setting Global Defaults for Resource Meta-Attributes

To set a default value for a resource option, add it to the rsc_defaults section with crm_attribute. For example,

# crm_attribute --type rsc_defaults --name is-managed --update false

would prevent the cluster from starting or stopping any of the resources in the configuration (unless of course the individual resources were specifically enabled by having their is-managed set to true).

5.4.3. Resource Instance Attributes

The resource agents of some resource standards (lsb, systemd and upstart not among them) can be given parameters which determine how they behave and which instance of a service they control.

If your resource agent supports parameters, you can add them with the crm_resource command. For example,

# crm_resource --resource Public-IP --set-parameter ip --parameter-value 192.0.2.2

would create an entry in the resource like this:

An example OCF resource with instance attributes

<primitive id="Public-IP" class="ocf" type="IPaddr" provider="heartbeat">
   <instance_attributes id="params-public-ip">
      <nvpair id="public-ip-addr" name="ip" value="192.0.2.2"/>
   </instance_attributes>
</primitive>

For an OCF resource, the result would be an environment variable called OCF_RESKEY_ip with a value of 192.0.2.2.

The list of instance attributes supported by an OCF resource agent can be found by calling the resource agent with the meta-data command. The output contains an XML description of all the supported attributes, their purpose and default values.

Displaying the metadata for the Dummy resource agent template

# export OCF_ROOT=/usr/lib/ocf
# $OCF_ROOT/resource.d/pacemaker/Dummy meta-data

<?xml version="1.0"?>
<!DOCTYPE resource-agent SYSTEM "ra-api-1.dtd">
<resource-agent name="Dummy" version="2.0">
<version>1.1</version>

<longdesc lang="en">
This is a dummy OCF resource agent. It does absolutely nothing except keep track
of whether it is running or not, and can be configured so that actions fail or
take a long time. Its purpose is primarily for testing, and to serve as a
template for resource agent writers.
</longdesc>
<shortdesc lang="en">Example stateless resource agent</shortdesc>

<parameters>
<parameter name="state" unique-group="state">
<longdesc lang="en">
Location to store the resource state in.
</longdesc>
<shortdesc lang="en">State file</shortdesc>
<content type="string" default="/var/run/Dummy-RESOURCE_ID.state" />
</parameter>

<parameter name="passwd" reloadable="1">
<longdesc lang="en">
Fake password field
</longdesc>
<shortdesc lang="en">Password</shortdesc>
<content type="string" default="" />
</parameter>

<parameter name="fake" reloadable="1">
<longdesc lang="en">
Fake attribute that can be changed to cause a reload
</longdesc>
<shortdesc lang="en">Fake attribute that can be changed to cause a reload</shortdesc>
<content type="string" default="dummy" />
</parameter>

<parameter name="op_sleep" reloadable="1">
<longdesc lang="en">
Number of seconds to sleep during operations.  This can be used to test how
the cluster reacts to operation timeouts.
</longdesc>
<shortdesc lang="en">Operation sleep duration in seconds.</shortdesc>
<content type="string" default="0" />
</parameter>

<parameter name="fail_start_on" reloadable="1">
<longdesc lang="en">
Start, migrate_from, and reload-agent actions will return failure if running on
the host specified here, but the resource will run successfully anyway (future
monitor calls will find it running). This can be used to test on-fail=ignore.
</longdesc>
<shortdesc lang="en">Report bogus start failure on specified host</shortdesc>
<content type="string" default="" />
</parameter>
<parameter name="envfile" reloadable="1">
<longdesc lang="en">
If this is set, the environment will be dumped to this file for every call.
</longdesc>
<shortdesc lang="en">Environment dump file</shortdesc>
<content type="string" default="" />
</parameter>

</parameters>

<actions>
<action name="start"        timeout="20s" />
<action name="stop"         timeout="20s" />
<action name="monitor"      timeout="20s" interval="10s" depth="0"/>
<action name="reload"       timeout="20s" />
<action name="reload-agent" timeout="20s" />
<action name="migrate_to"   timeout="20s" />
<action name="migrate_from" timeout="20s" />
<action name="validate-all" timeout="20s" />
<action name="meta-data"    timeout="5s" />
</actions>
</resource-agent>