Apps without a specified DFK should use the global DFK in scope at call time, not at other times.

[benclifford]

Often, apps are created with no specified DFK, and in that case they use a global dfk.

The global DFK which is in focus (i.e. stored in DataFlowKernelLoader._dfk) may change over time; for example, in pytest, and in interactive notebook sessions as people experiment.

The parsl code is a little vague on which global DFK will be used: the bash and python app decorators cache the global DFK inside the decorated app at first invocation, and use that forevermore - even if that DFK has been shutdown (a case which doesn't have clean error handling at the moment)

I posit that a user specifying no DFK will usually want to use the global DFK that is in focus at the time that they invoke the app, not at the time they first invoked the app; and that if they make separate invocations at different times with different DFKs in focus, then those different invocations should use those different DFKs.

If so, app decorators should not cache DFKs between calls.

[annawoodard]

Agreed!

[benclifford]

Fixed by #712

[benclifford]

duplicate of #626