The Stop Method

The Stop callback method of a resource type implementation is called by the RGM on a cluster node to stop the application. The callback semantics for the Stop method demands that:

• The Stop method must be idempotent because the Stop method can be called by the RGM even if the Start method did not complete successfully on the node. Thus the Stop method must succeed (exit zero) even if the application is not currently running on the cluster node and there is no work for it to do.

• If the Stop method of the resource type fails (exits non-zero) on a cluster node, the resource being stopped would end up in the STOP_FAILED state. Depending upon the Failover_mode setting on the resource, this may lead to a hard rebooting of the cluster node by the RGM. Thus it is important to design the Stop method so that it tries very hard to really stop the application, even by a hard and abrupt killing of the application (for example, using SIGKILL) if the application otherwise fails to terminate. It should also make sure that it does so in a timely fashion, because the framework treats expiry of Stop_timeout as a stop failure, and puts the resource in STOP_FAILED state.

The DSDL utility scds_pmf_stop() should suffice for most applications as it first attempts to softly (via SIGTERM) stop the application (it assumes that it was started under PMF via scds_pmf_start()) followed by a delivering a SIGKILL to the process. See PMF Functions for details about this utility.

Following the model of the code we have been using so far, assuming that the application specific function to stop the application is called svc_stop() (whether the implementation of svc_stop() uses the scds_pmf_stop() is besides the point here, and would depend upon whether or not the application was started under PMF via the Start method)) the Stop method can be implemented as

if (scds_initialize(&handle, argc, argv)!= SCHA_ERR_NOERR)
{
   return (1);   /* Initialization Error */
}
return (svc_stop(handle));

The svc_validate() method is not used in the implementation of the Stop method, because even if the system currently has a problem, the Stop method should attempt to stop the application on this node.