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Jobs currently fall into two broad types: singletons, where only one instance of the job may be active at any one time; and instance jobs where any number may be active, and all start requests start a new instance. This specification proposes the addition of a third type, jobs where the number of instances is limited by giving each a unique name; only a new name will start a new instance.


In practice, unlimited-instance jobs are quite rare and difficult to use since any number can be running at once thus contention of resources and locking become an issue. While the ["Resources"] specification attempts to resolve the locking issues, this would cause new instances to be queued after the active one instead of just re-using the active one.

Use cases


This scope of this specification is limited to the addition of an intermediate instance limitation between singleton and unlimited; no other issues are addressed.



Data preservation and migration

These changes are backwards compatible with the previous behaviour, since they only add new functionality.

NamedInstances (last edited 2008-03-08 14:19:52 by scott)