4 February 2011
This has been a long time in coming, but now with the next major ARC release we are approaching EOL for the arc0 code based Grid Manager. Removing the old Grid Manager code base has been one of the long-time planned major changes on our Roadmap.
Until now, the key Grid Manager component, released as part of the production ARC releases (0.4.x, 0.6.x, 0.8.x), has been taken from the arc0 code base and been packaged and distributed as the nordugrid-arc-grid-manager binary package. Earlier you have installed "nordugrid-arc-grid-manager", configured the service with arc.conf (even earlier with nordugrid.conf) and started the daemon with /etc/init.d/grid-manager start.
During the past years the Grid Manager code has been re-factored and migrated over to the new code base, carefully trying to keep all the existing functionality. All in all, the old Grid Manager code of arc0 has been re-engineered to a more sustainable and extendable solution that is now part of the new code base. With this refactoring came a new name that you may have heard before: A-REX. It is the core component of the ARC Compute Element (execution service).
The A-REX component is basically the old Grid Manager code resurrected in a new framework and extended with additional capabilities. A-REX comes with the same Grid Manager feature set (e.g. up/downloaders, cache, accounting, RTEs, LRMS, etc..), can be configured via the same old arc.conf and it is able to handle jobs submitted through gridftp jobplugin interface. For backwards compatibility, A-REX seamlessly works together with the LDAP-based ARC infosystem (ARIS) in order to publish information about cluster, queues and jobs through the usual schemas and LDAP interface. Running A-REX as a replacement of Grid Manager should be completely transparent for a site and will not require any configuration change. Furthermore, users and clients accessing an A-REX powered computing element should not see any difference since the interfaces are kept the same (gridftp and LDAP).
To get A-REX you will need to install the new "nordugrid-arc-arex" package and start the service with /etc/init.d/a-rex start (there'll be a compatibility grid-manager symlink provided too). By default, A-REX will use the config file from the old Grid Manager. The intention is that that's all the difference you as system administrators should see. Furthermore, if you are running a recent production ARC release (0.8.3.x) a smooth update path with binary packages will also be provided.
With the new A-REX comes lots of new features, among others job submission through a common WS interface of EMI, support for JSDL job description and a GLUE2 information publishing, extended powerful security framework. These features are not yet enabled by default, but in near future will become the only supported ones.
The next ARC release expected in February 2011 will contain A-REX that incorporates all the migrated Grid Manager code, and no other execution service. The old Grid Manager based on the arc0 code base will not be part of the release. Please note, the next major ARC release will also be the base for EMI and UMD releases, that means the old Grid Manager will not be included in the EMI or UMD releases either. Old pre-WS interfaces will be phased out gradually, in coordination with infrastructures.
The old Grid Manager, as part of the ARC 0.8.3.x production release will get security fixes at least the coming 6 months, but besides that, our intention is for the 0.x series to go EOL in February 2011.