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11.2.2 Enhancements in Job and Workflow Management
The MoSGrid science gateway offers end-users workflows whose execution
requires multisite, high-performance computing resources in order to be completed
in an acceptable time frame. Additionally, MoSGrid is targeted to help students and
researchers af
liated at German institutions; therefore, a mechanism to distinguish
allowed users had to be implemented. To ful
ll these requirements, MoSGrid needs
to incorporate access to high-computing resources via the use of personal X.509
certi
cates (ITU 1998) issued by appropriate German grid computing centers. In
order to satisfy the MoSGrid science gateway requirements, a suitable grid mid-
dleware system had to be chosen, and we found that UNICORE satis
ed all of
MoSGrid
is needs. UNICORE is a service-oriented, reliable, powerful grid mid-
dleware system (Streit 2010). It contains a mature workflow engine that was
originally developed for the computational chemistry community in the project
Chemomentum (Schuller 2008) and provides developers access to server compo-
nents such as computing and data resources via a complete software stack. Fur-
thermore, UNICORE is a mature solution that has been developed in several
German and European institutes since 1997. Interaction from the client-side is
achieved via web services using XML-based standards (e.g., JSDL (Anjomshoaa
2005), XACML (2005)).
'
11.2.2.1 UNICORE Submitter
The interaction between gUSE and external, remote high-computing infrastructures
is realized through the use of the DCI Bridge. Since it was desired that MoSGrid
users could perform common tasks on workflows and jobs such as submission,
suspension, termination and monitoring, the UNICORE plugin of DCI Bridge was
developed to ful
is needs, but it is also now part of the standard gUSE
distribution. The submitter interacts directly with UNICORE middleware systems
via the UNICORE API, which it also handles authorization and authentication.
Workflows are composed of individual jobs, and this fundamental concept is
reflected by both UNICORE and gUSE. Typically, each individual job represents a
task executed by a tool (e.g., an executable binary or a script). Individual tools in a
UNICORE-managed grid can be made available to UNICORE clients by adding the
appropriate entries into the Incarnation DataBase (IDB) (XNJS 2014) using a
simple text editor. The UNICORE submitter incorporates the selection of tools for
individual jobs in the creation of gUSE workflows; it accesses UNICORE
ll MoSGrid
'
s IDB via
the provided API and exposes all available tools in WS-PGRADE in a seamless
way for end users to select (Fig.
11.2
). The lack of selection of single tools in gUSE
is not a limitation of gUSE per se. This is due to the fact that conventional mid-
dleware systems do not provide clients with a database of available tools. If such a
database exists for a given middleware system, it would be possible to incorporate
single tool selection for gUSE jobs. Exactly this happens for the tools/applications
'
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