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Developing Data Services

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Updated: August 2018

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 demand the following factors:

  • 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 nonzero) on a cluster node, the resource that is being stopped enters the STOP_FAILED state. Depending on the Failover_mode setting on the resource, this condition might lead the RGM to perform a hard reboot of the cluster node.

    Thus, you must design the Stop method so that this method definitely stops the application. You might even need to resort to using SIGKILL to kill the application abruptly if the application otherwise fails to terminate.

    You must also ensure that this method stops the application in a timely fashion because the framework treats expiry of the Stop_timeout property as a stop failure, and consequently puts the resource in a STOP_FAILED state.

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

Assuming that the application-specific function that stops the application is called svc_stop(), implement the Stop method as follows:

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

Whether or not the implementation of the preceding svc_stop() function includes the scds_pmf_stop() function is irrelevant. Your decision to include the scds_pmf_stop() function depends on whether or not the application was started under the PMF through the Start method.

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