Information Technology Reference
In-Depth Information
No event
Event occur
Event
registration
Event
processing
Waiting
All inputs are not ready
Initial state
State
Find a suitable
resource
Job
submitting
Resource
matching
Final state
Submitted
Remote node failed
Job completed
Monitoring
Output processing
Processed
FIGURE 5.5
State transition of TM.
tasks and waits for the events to occur; when an event occurs, the TM goes
to
the
event processing
state. If all input data are available, it starts a new
thread to process execution for a job; otherwise, the TM goes back to the
wait
state. A job is a unit of work that a TM sends to a grid node and one
task may create more than one job. The job execution is started from
resource matching
, in which a suitable resource is selected from the resource
group created by querying a directory service. If a suitable resource is
available, the TM submits a job to the resource and then monitors the
status of job execution on the remote resource. If the execution has failed,
the TM goes back to
resource matching
and selects an alternative resource
and then submits the job to it. If all parent tasks and execution jobs are
completed, the TM ends.
5.3.3 Interaction
The interactions between the WCO, TMs, ESS, and remote resources are
illustrated in
Figure 5.6
. First, the WCO needs to register to the ESS and to
task status events. Then, the WCO activates TMS of i rst-level tasks of
which, in this example, there is only one TM1. After TM1 i nishes the pre-
processing for the task execution, it sends a message to ESS saying “
I am
executing the task
.” ESS informs the WCO and WCO activates TMs of the
child tasks of TM1, namely TM2 and TM3, in this example.
The inputs of the task managed by TM2 and TM3 rely on the output of
the task of TM1, so TM2 and TM3 register to ESS and listen to its output
events. Once TM1 identii es a suitable resource, it submits a task to that
resource. As soon as TM1 knows the output of the task, it informs TM2
Search WWH ::
Custom Search