Fix unbounded growth of Model._event_generators#3317
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Change Model._event_generators from a list to a set and move registration responsibility into EventGenerator. EventGenerator now adds itself to model._event_generators when scheduled and discards itself on stop/cancel; the model no longer appends generators. This avoids duplicate entries, enables O(1) add/remove, and keeps strong references to active generators to prevent GC.
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When designing this part I thought this would be a problem, because now an EventGenerator can't be restarted anymore. But that's not true, because:
So this nicely solves itself. |
EwoutH
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What do you mean by restarting? |
quaquel
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Feb 15, 2026
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Calling .start() after you have called .stop() |
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Fair enough. |
Krishsharma179
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Feb 21, 2026
Change Model._event_generators from a list to a set and move registration responsibility into EventGenerator. EventGenerator now adds itself to model._event_generators when scheduled and discards itself on stop/cancel; the model no longer appends generators. This avoids duplicate entries, enables O(1) add/remove, and keeps strong references to active generators to prevent GC.
EwoutH
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Summary
Model._event_generatorsgrows unbounded because exhausted and stoppedEventGenerators are never removed.Bug / Issue
_event_generatorsexists solely to hold strong references to active generators, preventing garbage collection. However, generators were never removed when they finished or were stopped, causing the list to grow indefinitely. Since generators hold hard references to their callables (which may be bound agent methods), this could also prevent agents from being garbage collected.Closes #3313.
Implementation
_event_generatorsfromlisttoset(ordering is irrelevant for a GC-prevention container).EventGenerator:start()adds itself to the set,stop()and exhaustion remove it viadiscard()._event_generators.append()call fromModel.schedule_recurring, sincestart()now handles it.Testing
Existing tests pass. Could add a test verifying that a generator with
count=nis removed from_event_generatorsafter completing its executions.Additional Notes
No public API changes,
_event_generatorsis a private attribute.