Starting and Stopping a Data Service

A Start method is expected to perform the actions required to start a data service on a cluster node. Typically, this includes retrieving the resource properties, locating application-specific executables and configuration files, and launching the application with the appropriate command-line arguments.

The scds_initialize function retrieves the resource configuration. The Start method can use property convenience functions to retrieve values for specific properties, such as Confdir_list, that identify the configuration directories and files for the application to launch.

A Start method can call scds_pmf_start to launch an application under control of the Process Monitor Facility (PMF). PMF enables you to specify the level of monitoring to apply to the process and provides the ability to restart the process in case of failure. See xfnts_start Method for an example of a Start method implemented with the DSDL.

A Stop method must be idempotent such that it exits with success even if it is called on a node when the application is not running. If the Stop method fails, the resource being stopped is set to the STOP_FAILED state, which can lead to a hard reboot of the cluster.

To avoid putting the resource in STOP_FAILED state the Stop method must make every effort to stop the resource. The scds_pmf_stop function provides a phased attempt to stop the resource. It first attempts to stop the resource using SIGTERM signal, and if this fails, uses a SIGKILL signal. See scds_pmf_stop(3HA) for details.