generalize the TT / JT servers to handle more generic tasks

We've been discussing a proposal to generalize the TT / JT servers to handle more generic tasks and move job specific work out of the job tracker and into client code so the whole system is both much more general and has more coherent layering. The result would look more like condor/pbs like systems (or presumably borg) with map-reduce as a user job.

Such a system would allow the current map-reduce code to coexist with other work-queuing libraries or maybe even persistent services on the same Hadoop cluster, although that would be a stretch goal. We'll kick off a thread with some documents soon.

Our primary goal in going this way would be to get better utilization out of map-reduce clusters and support a richer scheduling model. The ability to support alternative job frameworks would just be gravy!

Putting this in as a place holder. Hope to get folks talking about this to post some more detail.