To express their interest in events published by other
components, subscribers can use the
ham_condition_state() and
ham_condition_raise() API calls.
These are similar to the
ham_condition()
API call (e.g., they return a handle to a condition), but they allow the
subscriber customize which of several possible published
conditions they're interested in.
- Trigger based on state transition
- When an entity publishes a state transition, a state transition condition
is raised for that entity, based on the two states involved in the transition (the
from state and the to state).
Subscribers indicate which states they're interested in by specifying
values for the fromstate and tostate
parameters in the
ham_condition_state
API call.
- Trigger based on specific published condition
- To express interest in conditions raised by entities, subscribers can use the API call
ham_condition_raise(),
indicating as parameters to the call what sort of conditions they're interested in.
For more information, see the API reference documentation in the
High Availability Framework Developer's Guide.