HP Serviceguard manual How Packages Run, What Makes a Package Run?

How Packages Run

Packages are the means by which Serviceguard starts and halts configured applications. Failover packages are also units of failover behavior in Serviceguard. A package is a collection of services, disk volumes and IP addresses that are managed by Serviceguard to ensure they are available.

There can be a maximum of 300 packages per cluster and a total of 900 services per cluster.

What Makes a Package Run?

There are 3 types of packages:

•The failover package is the most common type of package. It runs on one node at a time. If a failure occurs, it can switch to another node listed in its configuration file. If switching is enabled for several nodes, the package manager will use the failover policy to determine where to start the package.

•A system multi-node package runs on all the active cluster nodes at the same time. It can be started or halted on all nodes, but not on individual nodes.

•A multi-node package can run on several nodes at the same time. If auto_run is set to yes, Serviceguard starts the multi-node package on all the nodes listed in its configuration file. It can be started or halted on all nodes, or on individual nodes, either by user command (cmhaltpkg) or automatically by Serviceguard in response to a failure of a package component, such as service, EMS resource, or subnet.

System multi-node packages are supported only for use by applications supplied by Hewlett-Packard.

A failover package can be configured to have a dependency on a multi-node or system multi-node package. The package manager cannot start a package on a node unless the package it depends on is already up and running on that node.

The package manager will always try to keep a failover package running unless there is something preventing it from running on any node. The most common reasons for a failover package not being able to run are that auto_run is disabled so Serviceguard is not allowed to start the package, that node switching is disabled for the package on particular nodes, or that the package has a dependency that is not being met. Package weights and node capacities, if you choose to use them, also determine whether a package can run on a given node. When a package has failed on one node and is enabled to switch to another node, it will start up automatically in a new location where its dependencies and all other necessary conditions are met. This process is known as package switching, or remote switching.

A failover package starts on the first available node in its configuration file; by default, it fails over to the next available one in the list. Note that you do not necessarily have to use a cmrunpkg command to restart a failed failover package; in many cases, the best way is to enable package and/or node switching with the cmmodpkg command.

When you create the package, you indicate the list of nodes on which it is allowed to run. System multi-node packages must list all cluster nodes in their cluster. Multi-node packages and failover packages can name some subset of the cluster’s nodes or all of them.

If the auto_run parameter is set to yes in a package’s configuration file Serviceguard automatically starts the package when the cluster starts. System multi-node packages are required to have auto_run set to yes. If a failover package has auto_run set to no, Serviceguard cannot start it automatically at cluster startup time; you must explicitly enable this kind of package using the cmmodpkg command.

NOTE: If you configure the package while the cluster is running, the package does not start up immediately after the cmapplyconf command completes. To start the package without halting and restarting the cluster, issue the cmrunpkg or cmmodpkg command.

How does a failover package start up, and what is its behavior while it is running? Some of the many phases of package life are shown in Figure 22.

60 Understanding Serviceguard Software Components