Appendix H: Interfacing to Maui
Maui interfaces to systems providing various services and using various protocols. This appendix is designed to assist users who wish to enable Maui in new environments using one of the existing interfaces. It does not cover the steps required to create a new interface.
H.1 Utilizing Maui Client Services
The standard Maui distribution provides a scheduler server (maui) and a number of user clients (showq, showres, etc). By default, these clients communicate with the scheduler using an internal single use, 'byte count + secret key' based TCP connection protocol called simply the 'SingleUseTCP' protocol. This protocol is documented in the Wiki 'Socket Interface ' section with an overview and sample code describing how to generate the byte count, timestamp, encrypted checksum, etc. This protocol is functional but is not a commonly used standard outside of the Maui project. A further issue with creating client interfaces is that even though the socket interface is well defined, the data flowing through this interface to support client requests is not standardized. As of Maui 3.2.5, some clients receive raw binary data, others raw text, and still others formatted text ready for display. This has resulted from the evolutionary nature of the client interface which has not received a much needed design 'refresh'. The good news is that this refresh is now under way.
As part of the Department of Energy's 'Scalable Systems Software' initiative, there have been significant enhancements to the scheduler/client protocol. Maui now supports multiple socket level protocol standards in communicating with its clients and peer services. These including 'SingleUseTCP', 'SSS-HALF', and 'HTTP'. The client socket protocol can be specified by setting the MCSOCKETPROTOCOL parameter to SUTCP , SSS-HALF, or HTTP. Further protocols are being defined and standardized over time and backwards compatibility will be maintained. Documentation on the SSS-HALF implementation can be found within the DOE's SSS Project Notebooks . NOTE: HTTP support is currently (Oct 24, 2002) in active development and is not expected to be in production use until Maui 3.2.6.
In addition to the socket protocol advances, there has also been work in the area of standardizing the format in which the client data is actually transmitted. The SSS project has selected XML as the means to frame all inter-client data. To date, a number of Maui clients have been ported over to enable optional use of XML based data framing. These clients include mshow (showq), showstate, checknode , mjobctl (runjob, setjobhold, setspri, canceljob), and mresctl (setres, releaseres). NOTE: The XML used in these clients is still evolving. It is expected to be finalized for the clients listed by mid December 2002. If there is interest in working with these protocols or defining specifications, please contact us so we can coordinate any changes and take your needs into account when prioritizing future development.
H.2 Resource Management Interfaces
H.3 Allocation Management Interfaces
H.4 Grid Scheduling System Interfaces
H.5 Information Service Interfaces
H.6 Event Management Services
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