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All metrics listed above are simply cumulative sums of the number of tasks/agents in each respective state. Thus, since these are cumulative sums, it is expected that the created-task-count = running-task-count = done-task-count when a Trogdor cluster has finished all tasks. 

Proposed Changes

We propose adding a TrogdorMetrics class to Trogdor that exposes the aforementioned metrics.  Since Trogdor agents and tasks share a common Platform class, a TrogdorContainer class will be created inside the Platform class to allow for the creation of a shared TrogdorMetrics instance between the Agent and Coordinator classes.

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However, by way of simple mathmathematics, we are able to deduce the number of pending tasks by simply subtracting the number of pending tasks from those that are running and done. Similarly, we are able to deduce the number of running tasks from those that are pending and done. The number of done tasks will be the true number of done tasks, with no mathematics necessary. This allows for the tracking of fewer metrics. The STOPPING state is more of a transient state and thus doesn’t add too much significance to metrics, so it was deemed useful to only have metrics tracking PENDING, RUNNING, and DONE tasks.