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FAQ: lcg-ce to cream-ce

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The FAQ provides the questions and answers those may arise for the user communities during the transition from lcg-ce to cream-ce. It does not replace the CREAM User Guide (see the references section), but it provides a list of pointers to relevant documentation.

Q1: What is cream-ce?

The CREAM (Computing Resource Execution And Management) Service is a simple, lightweight service that implements all the operations at the Computing Element (CE) level; its well-defined Web Service-based interface and its implementation as an extension of the Java-Axis servlet (running inside the Apache Tomcat container) provide interoperability with clients written in any programming language and running on any computer platform.

The CREAM interface is well-defined using the Web Service Description Language (WSDL); anyone can generate his/her CREAM client by simply filling in the stub code generated by WSDL parser (gSOAP for C/C++, Axis for Java, Perl module for perl).

The CREAM architecture is illustrated here: Diagram

Q2: What batch systems are supported by CREAM?

LSF, Torque

Q3: How does proxy credential delegation and proxy renewal work in CREAM?

Detailed documentation about security-related aspects of CREAM are available at the CREAM User Guide.

Q4: how are jobs submitted to CREAM?

CREAM has ability to accept either direct Jobs from gLite-UI, SOAP clients or any other developed UIs based on web-services or Jobs sent through WMS. Jobs can be controlled through operations such as suspend, resume and delete.

In case of submission through the Workload Management System (WMS), the ICE (Interface to CREAM Environment) component of the WMS is used. To select the CREAM instances to which the job can be submitted, submission criteria can be defined by means of the Job Description Language - JDL (see the CREAM JDL Guide).

Intructions for the management of input and output files are available here.

Q5: is the performance of CREAM comparable to the one of the lcg-ce?

CREAM has been intentionally designed to deliver higher performance than lcg-ce.


Q6: What client errors are returned by CREAM? These are documented here: Cream Client Error Messages

Q7: Where can I find more information about the known issues of CREAM?

The known issues of current CREAM software in production release are documented here:

Q: Where can I find more documentation about CREAM?

Q8: How can I get support about CREAM? You are recommended to submit a ticket to the EGI Helpdesk system (GGUS).