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How to drain a CE
To indicate to clients that a CE is being drained (i.e. new jobs must not be sent to that CE) at least the information system should be updated.
Well-behaved clients will consult the BDII to discover if a particular CE is ready for new jobs. The relevant attribute is GlueCEStateStatus, which can take any of the following official values per queue:
- Production: the queue accepts jobs and is served by the scheduler. Jobs should be sent only when the queue is in this state.
- Draining: the queue does not accept jobs, but is served by the scheduler. This is the state to be advertised for all queues served by the CE when the CE needs to be drained.
- Queueing: the queue accepts new jobs, but is not served by the scheduler.
- Closed: the queue does not accept jobs and is not served by the scheduler.
For a CREAM CE actual job submissions can be prevented with the glite-ce-disable-submission command, but one should still ensure the information system shows that the CE is being drained, to avoid that jobs are sent to the CE only to fail immediately.
For PBS/Torque systems the info provider will automatically determine the correct value for GlueCEStateStatus per queue based on whether the queue has been enabled and whether it has been started. If you have a single CE or you want to drain all your CEs, you can adjust the values like this:
# qmgr -c "set queue myqueue enabled=<True|False>" # qmgr -c "set queue myqueue started=<True|False>"
If you have multiple CEs in front of the same batch system and you want to drain only some of the CEs, on those CEs you can edit the glite-info-dynamic-ce plugin like this (lines wrapped for readability):
#!/bin/sh /opt/lcg/libexec/lcg-info-dynamic-pbs \ /opt/glite/etc/gip/ldif/static-file-CE.ldif <your-CE> | sed -e 's/GlueCEStateStatus: Production/GlueCEStateStatus: Draining/'
The latter method works for any batch system.