Package ganeti :: Module cmdlib :: Class Tasklet

Class Tasklet

Tasklet base class.

Tasklets are subcomponents for LUs. LUs can consist entirely of tasklets or they can mix legacy code with tasklets. Locking needs to be done in the LU, tasklets know nothing about locks.

Subclasses must follow these rules:

Implement CheckPrereq
Implement Exec

Instance Methods

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__init__(self, lu)

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CheckPrereq(self)
Check prerequisites for this tasklets.

source code

Exec(self, feedback_fn)
Execute the tasklet.

source code

Method Details

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CheckPrereq(self)

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Check prerequisites for this tasklets.

This method should check whether the prerequisites for the execution of this tasklet are fulfilled. It can do internode communication, but it should be idempotent - no cluster or system changes are allowed.

The method should raise errors.OpPrereqError in case something is not fulfilled. Its return value is ignored.

This method should also update all parameters to their canonical form if it hasn't been done before.

Exec(self, feedback_fn)

source code

Execute the tasklet.

This method should implement the actual work. It should raise errors.OpExecError for failures that are somewhat dealt with in code, or expected.