WEB server ( load balancer ). …. CREAM. CREAM. CREAM. LRMS. EMI-ES. EMI-ES. EMI-ES. CREAM-CE. CREAM-CE status and evolution plans. Definition and adoption of job related standard interfaces.
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CREAM-CE status and evolution plans
Definition and adoption of job related standard interfaces
The CREAM-CE implements a Grid job management service available to end users and to other higher level Grid job submission services. It allows the submission, management and monitoring of computational jobs to Local Resource Management Systems (LRMS).
Now facing the challenge to support an enlarged community of users, as part of the European Middleware Initiative (EMI), such service needs to be consolidated and evolved.
Among the new functionalities introduced with the first EMI release (EMI-1), we highlight the integration with the new authorization framework (ARGUS). The major developments foreseen for the next EMI release include the adoption of job related standard interfaces (EMI-ES) and the enhancing of CREAM with the High Availability (HA) criteria based on the clustered approach.
Several services providing compute and job related functionality have been implemented in the context of different Grid projects. However these services, which provide the same core functionality, have been realized by adopting proprietary solutions. While standard mechanisms for job description (e.g. JSDL) and standard interfaces for job submission and management do exist (e.g. BES), they are not really suited for production use because they lack significant capabilities.
Towards the CREAM High Availability
Paolo Andreetto, Sara Bertocco, Alvise Dorigo, Eric Frizziero, Alessio Gianelle, Massimo Sgaravatto, Lisa Zangrando
One of the main objectives described in the CREAM evolution plan, is the need to meet the High Availability (HA) criteria. In particular, CREAM, like several popular Internet services, must rely on large clusters of commodity computers for providing several features, including high performance, scalability, availability and fault tolerance. From the user's point of view the main benefit provided by this enhancement is the guaranteed access to his own jobs and related resources (i.e. job sandbox) during planned and unplanned outages. So, we are focusing on providing CREAM with the ability to be continuously available for serving the user requests independently of eventual current critical conditions.
The figure illustrates the high level CREAM clustered architecture which is based on a horizontal topology. We define a CREAM node as a separate CREAM instance running on its dedicated (virtual) machine, while a collection of such nodes is referred as CREAM cluster. The WEB server (e.g. Apache) acts as gateway for incoming requests of authenticated users. These requests are delivered to the load balancer which redirects them to the proper CREAM nodes, basing its decisions on the selected scheduling algorithm (e.g. Round Robin, Weight based, etc). Moreover the load balancer can provide even fault tolerance capability, if appropriately configured.
ARGUS as the unique authorization mechanism
The use of different authorization mechanisms, each providing the same or similar functionalities is clearly a complication from a deployment and maintenance point of view. Moreover because of bugs or misconfigurations, inconsistent authorization decisions could be made. These issues have been addressed by the EMI project by referring to a single authorization service (ARGUS) which is supposed to be the unique authorization service for all EMI services.
The integration with the ARGUS service has been introduced in the first EMI release (EMI-1).
Contact: gLite job management product team
For more information: www.eu-emi.eu