Red Hat Training

A Red Hat training course is available for Red Hat Enterprise Linux

7.3. Moving Resources Due to Connectivity Changes

Setting up the cluster to move resources when external connectivity is lost is a two-step process.
  1. Add a ping resource to the cluster. The ping resource uses the system utility of the same name to test if a list of machines (specified by DNS host name or IPv4/IPv6 address) are reachable and uses the results to maintain a node attribute called pingd.
  2. Configure a location constraint for the resource that will move the resource to a different node when connectivity is lost.
Table 5.1, “Resource Properties” describes the properties you can set for a ping resource.

Table 7.1. Properties of a ping resources

FieldDescription
dampen
The time to wait (dampening) for further changes to occur. This prevents a resource from bouncing around the cluster when cluster nodes notice the loss of connectivity at slightly different times.
multiplier
The number of connected ping nodes gets multiplied by this value to get a score. Useful when there are multiple ping nodes configured.
host_list
The machines to contact in order to determine the current connectivity status. Allowed values include resolvable DNS host names, IPv4 and IPv6 addresses.
The following example command creates a ping resource that verifies connectivity to www.example.com. In practice, you would verify connectivity to your network gateway/router. You configure the ping resource as a clone so that the resource will run on all cluster nodes. 
# pcs resource create ping ocf:pacemaker:ping dampen=5s multiplier=1000 host_list=www.example.com --clone
The following example configures a location constraint rule for the existing resource named Webserver. This will cause the Webserver resource to move to a host that is able to ping www.example.com if the host that it is currently running on cannot ping www.example.com 
# pcs constraint location Webserver rule score=-INFINITY pingd lt 1 or not_defined pingd