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Workflow coordinator
Notify
Control
Notify
User
portal
Event service
Status
Output
Notify
......
Task manager
Task manager
Task manager
Grid resources
FIGURE 5.3
Event-driven mechanism.
5.3.2 State Transition
The state transition of a WCO is illustrated in Figure 5.4. WCO registers
with the ESS and start TMs of i rst-level tasks and then monitors activated
TMs. Upon receiving execution status from a TM, WCO starts the TMs of
its child tasks. If WCO receives a status
done
event, it checks whether other
TMs are still running. If so, WCO goes back to
monitoring
, otherwise
it exits. If WCO receives a failed event from a TM, it proceeds to
failure
processing
, and then ends.
The state transition of TMs is illustrated in
Figure 5.5
.
The TM registers
events, such as output events and status events, generated by its parent
No event
Status event
registration
First level
TMs activation
Monitoring
Executing
event
Done
event
succeeded
a TM is
executing
Failed
event
Workflow
execution
checking
Child TMs
activation
Failure
processing
Initial state
State
No TM is running
Final state
FIGURE 5.4
State transition of WCO.
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