tree af368cdb76cc0d8b585b9a28ac013333d1640362
parent 9ac5e40654b712dcd491aef2605d0e0b3b30957e
author Jake Biesinger <jake.biesinger@gmail.com> 1385541982 -0800
committer Jake Biesinger <jake.biesinger@gmail.com> 1385596593 -0800

add an "iteration complete" hook for aggregation/reporting across iterations

This commit allows the user to specify a class which will be called upon
completion of each pregelix iteration.  This allows us to perform a user-
specified action between iterations.

As an example, a PerIterationGlobalAggregatesHook is provided which
saves the complete set of global aggregator states from every iteration,
allowing the user to observe aggregates from all iterations.

The default hook does nothing.

The hook instance is attached directly to the PregelixJob so that it can
be retrieved by the Driver's caller.