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component:glitemce

modified gLite CE

The modified gLite CREAM computing element (mCE) is designed to forward jobs to the 3G Bridge service behind which desktop grid servers are receiving the jobs. The EDGI mCE has the following main tasks:

  1. to authorize the application against the target DG system,
  2. to convert the application description to the format the 3G Bridge (which is the job submission contact point of a desktop grid server) requires,
  3. to keep track of the status of the submitted job and
  4. to retrieve the results

There are two ways of job submission to the mCE. In case the application is registered in the target BOINC server, the user can send jobs referring to that particular application. The other possibility is to submit own binaries to a target BOINC server, but only if the “GBAC” virtualization framework is deployed on the BOINC server.

Submitting a registered application happens to refer the job binaries stored in the Application Repository by gsiftp URLs. The example (to submit a single binary job named “dsp”) shows that binaries in the InputSandbox must be referenced by URLs ("gsiftp://edgi-repo…") pointing to the EDGI AR.

Executable = "dsp";
Arguments = "-f 22 -i 22 -p 723 -n pools.txt";
InputSandbox = {
      "gsiftp://edgi-repo.cpc.wmin.ac.uk:2811/srv/edgi/1001/1102/dsp",
      "pools.txt" };
OutputSandbox = {"cost.txt"};

The URLs for the binaries can be queried from the EDGI AR. These URLs are used by the EDGI mCE to detect whether the user refers to a trusted application stored in the AR. Input and output files can be defined in a normal gLite way, no restriction is introduced. In the example above “pools.txt” is defined as input, and “cost.txt” is defined as output of the dsp job.

Submitting a non-registered application to the mCE can happen just the same way as submitting a normal gLite job.

Executable = "dsp";
Arguments = "-f 22 -i 22 -p 723 -n pools.txt";
InputSandbox = {"dsp","pools.txt"};
OutputSandbox = {"cost.txt"};

After the mCE recognizes the situation of submitting an own binary, the mCE checks the existence of the GBAC virtualization framework on the target BOINC project and enables the submission. Once the EDGI mCE has received the job and has extracted all the necessary information (application name, arguments, inputs, and outputs), submission to 3G Bridge is performed through its web-service interface. This interface is then used to keep track of the job status and to retrieve the result files.

The EDGI mCE is implemented as a new EDGI CREAM connector. The structure of the CREAM computing element allows attaching new connector components to handle different backend grids or clusters. The EDGI CREAM connector has the task to intercept the gLite jobs, and send them to a target 3G Bridge service. Thus, from higher level CREAM component's point of view the new connector behaves like a batch system implementation with the difference that the job is not to run on a Worker Node belonging to the CREAM CE, but is sent to a 3G Bridge service for execution by a desktop grid system behind.

For installation instructions, see the gLite mCE installation manual.

component/glitemce.txt · Last modified: 2013/01/15 14:34 by smith