Clustering
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Swift can group a number of short job submissions into a single larger job
submission to minimize overhead involved in launching jobs (for example, caused
by security negotiation and queuing delay). In general, coasters should be used
in preference to the clustering mechanism documented in this section.

By default, clustering is disabled. It can be activated by setting the
clustering.enabled property to true.

A job is eligible for clustering if the GLOBUS::maxwalltime profile is
specified in the tc.data entry for that job, and its value is less than the
value of the clustering.min.time property.

Two or more jobs are considered compatible if they share the same site and do
not have conflicting profiles (e.g. different values for the same environment
variable).

When a submitted job is eligible for clustering, it will be put in a clustering
queue rather than being submitted to a remote site. The queue is processed at
intervals specified by the clustering.queue.delay property. The processing of
the clustering queue consists of selecting compatible jobs and grouping them
into clusters whose maximum wall time does not exceed twice the value of the
clustering.min.time property.