Retire FakeFiber #1238
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Retire FakeFiber #1238
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FakeFiber was used by KafkaConsumer to manage: 1. the consumerActor fiber, processing requests (including polls); 2. the pollScheduler fiber, scheduling poll requests (subject to backpressure); 3. a fiber combining the above two fibers. Compared to a regular fiber, FakeFiber offered a method to combine two fibers by racing them one against the other. The semantics were similar to the race method for effects, but operating at the fiber level. In KafkaConsumer, FakeFiber was used with cancellation effects that returned immediately (i.e., fiber.cancel.start.void). In addition the fiber outcome was relayed to KafkaConsumer.awaitTermination. With this change FakeFiber is replaced with an Async[F].race of the underlying effects. This is managed in the new method startBackgroundConsumer, which builds upon effects assembled by runConsumerActor and runPollScheduler. These effects are unwrapped from the previous fibers. As before, cancellation of the consumer effect is only waited on in awaitTermination, where any errors are propagated. Compared to the original behaviour of FakeFiber.combine, starting with cats-effect 3.5.0, cancellation of one of the consumer effects will lead to cancellation of both, as per changes introduced with typelevel/cats-effect#3453. I'm not sure how cancelation would come into play here, but the behaviour change looks appropriate: without one of the racing fibers KafkaConsumer would not be functional (no polls scheduled, or no requests/polls processed).
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As motivation for doing this, I'm running down different code paths trying to understand how partitions may get "lost", in relation to #1230. To be clear, I have not identified any issue with I do note that FakeFiber was introduced to support the upgrade to cats-effect 3.x, and that its behaviour seems to be well supported by racing the effects directly, instead. With this change the goal is to remove a little bit of legacy and hopefully reduce cognitive load as well. |
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FakeFiber was used by KafkaConsumer to manage:
Compared to a regular fiber, FakeFiber offered a method to combine two fibers by racing them one against the other. The semantics were similar to the race method for effects, but operating at the fiber level.
In KafkaConsumer, FakeFiber was used with cancellation effects that returned immediately (i.e., fiber.cancel.start.void). In addition the fiber outcome was relayed to KafkaConsumer.awaitTermination.
With this change FakeFiber is replaced with an Async[F].race of the underlying effects. This is managed in the new method startBackgroundConsumer, which builds upon effects assembled by runConsumerActor and runPollScheduler. These effects are unwrapped from the previous fibers.
As before, cancellation of the consumer effect is only waited on in awaitTermination, where any errors are propagated.
Compared to the original behaviour of FakeFiber.combine, starting with cats-effect 3.5.0, cancellation of one of the consumer effects will lead to cancellation of both, as per changes introduced with typelevel/cats-effect#3453. I'm not sure how cancelation would come into play here, but the behaviour change looks appropriate: without one of the racing fibers KafkaConsumer would not be functional (no polls scheduled, or no requests/polls processed).