Defining RSCT resources for a high available web server

Learn more about the requirements for the high availability web server and the required RSCT resources.

The following example shows the definition of the necessary resources for a high available web server. The cluster that is named SA_Domain was previously created in Creating a cluster.

Requirements for the high available web server:
  • The web server can be started on any cluster node but can run on a single node at any point in time only.
  • When failures occur, the web server is restarted automatically on the same or on another node in the cluster. Utilize this relocation capability of the web server for planned outages of nodes during service and maintenance periods.
  • The web server must be addressable with the same IP address, regardless of the node it currently runs on. Thus the location of the web server is not apparent outside the cluster and no adaptation must be processed when the web server is moved to another node.
Three RSCT resources from different resource classes are required in RSCT:
  1. An application resource that is named apache2, which represents the web server daemon. Resource apache2 is from class IBM.Application, and is defined as floating resource, which is a term to describe the ability to move the resource between cluster nodes.
  2. A new extra IP address that is named apache2IP, which represents the web servers IP address. Resource apache2IP is from a class that is called IBM.ServiceIP and must be a floating resource too because it must follow the location of the web server.

    IBM.ServiceIP addresses are aliased as extra IP addresses on network interfaces.

  3. One network interface must be selected on each node that can host the IBM.ServiceIP address apache2IP. Network interfaces belong to the class IBM.NetworkInterface and must not be explicitly defined by the user but are auto-harvested by RSCT.