13.4 Adding New Resource Manager Interfaces
Maui interfaces with numerous resource management systems. Some of these interact through a resource manager specific interface (i.e., OpenPBS/PBSPro, Loadleveler, SGE) while others interact through generalized interfaces such as SSS or Wiki. (see the Wiki Overview). For most resource managers, either route is possible depending on where it is easiest to focus development effort. Use of Wiki generally requires modifications on the resource manager side while creation of a new resource manager specific Maui interface would require more changes to Maui modules. If a scheduling API already exists within the resource manager, creation of a resource manager specific scheduler interface is often selected.
Regardless of the interface approach selected, adding support for a new resource manager is typically a straight forward process for about 95% of all supported features. The final 5% of features usually requires a bit more effort as each resource manager has a number of distinct concepts which must be addressed.
13.4.1 Resource Manager Specific Interfaces
If the resource manger specific interface is desired, then typically a scheduling API library/header file combo is required. (i.e., for PBS, libpbs.a + pbs_ifl.h, etc.) This resource manager provided API provides calls which can be linked into Maui to obtain the raw resource manager data including both jobs and compute nodes. Additionally, this API should provide policy information about the resource manager configuration if it is desired that such policies be specified via the resource manager rather than the scheduler and that Maui know of and respect these policies. The new 'M<X>I.c' module would be responsible for loading information from the resource manager, translating this information, and then populating the appropriate scheduler data structures. The existing MLLI.c, MPBSI.c and MWikiI.c modules provide templates indicating how to do this.
The first step in this process is defining the new resource manager type. This is accomplished by modifying moab.h and MConst.c files to define the new RMTYPE parameter value. With this defined, the MRMI.c module must be modified to call the appropriate resource manager specific calls which will eventually be created within the 'M<X>I.c' module. This process is straightforward and involves extending existing resource manager specific case statements within the general resource manager calls.
The vast majority of the development effort is entailed in creating the resource manager specific data collection and job management calls. These calls populate Maui data structures, and are responsible for passing Maui scheduling commands on to the resource manager. The base commands are GetJobs, GetNodes, StartJob, and CancelJob but if the resource manager support is available, extended functionality can be enabled by creating commands to suspend/resume jobs, checkpoint/restart jobs, and/or allow support of dynamic jobs.
If the resource manager provides a form of event driven scheduling interface, this will also need to be enabled. The MPBSI.c module provides a template for enabling such an interface within the MPBSProcessEvent() call.
13.4.2 Wiki Interface
The Wiki interface is a good alternative if the resource manager does not already support some form of existing scheduling API. For the most part, use of this API requires the same amount of effort as creating a resource manager specific interface but development effort focused within the resource manager. Since Wiki is already defined as a resource manager type, no modifications are required within Maui. Additionally, no resource manager specific library or header file is required. However, within the resource manager, internal job and node objects and attributes must be manipulated and placed within Wiki based interface concepts as defined in the Wiki Overview. Additionally, resource manager parameters must be created to allow a site to configure this interface appropriately.
13.4.3 SSS Interface
The SSS interface is a new XML based generalized resource manager interface. It provides an extensible, scalable, and secure method of querying and modifying general workload and resource information.