====== Job resource manager ======

The part of OAR that is usually responsible for setting up and cleaning up the operating system of resources
given to a job is the ''job resource manager''.

This is a Perl script that is part of the OAR configuration files:
located on the OAR server in ''/etc/oar'' (see oar.conf). The default one provided with the OAR is named: ''/etc/oar/job_resource_manager_cgroup.pl''.


This Perl script is broadcasted (thanks to ''TakTuk'') to be executed on all the nodes of a job to initialize
the resources at the beginning (creating the job cgroups and more), and to clean-up the resources at the end (killing the remaining processes of the job, removing the job cgroups, and more).

This script can be modified or just augmented by admins: it is meant for
that, despite exposing a good part of the complexity of OAR.

Notes:
  * Contrary to the job ''prologue''/''epilogue'' which executes only on the head node of the job and contrary to the job ''server prologue''/''server epilogue'' which executes on the OAR server, the ''job resource manager'' executes on all the nodes of the job hosting resources of type ''default''.
  * It is possible to configure OAR do not use the ''job resource manager'', but this is not usual (no cgroup used) and has not been tested recently.
  * The ''job resource manager'' does not execute on the ''deploy'' frontend (for jobs of type ''deploy'') nor on the ''cosystem'' frontend (for jobs of type ''cosystem''): indeed OAR does not set up cgroups on frontends unlike on nodes. 
  * For jobs of type ''deploy'' or ''cosystem'', the job ''prologue''/''epilogue'' however executes on the ''deploy''/''cosystem'' frontend, and ''server prologue''/''server epilogue'' on the OAR server.
  * For jobs of type ''noop'', the job ''prologue''/''epilogue'' do not execute, but the ''server prologue''/''server epilogue'' do execute on the OAR server, as well as the job resource manager on all nodes hosting resources of type ''default''.