FSM fault injection #13419
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FSM fault injection #13419
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The plan applier has to get a snapshot with a minimum index for the plan it's working on in order to ensure consistency. Under heavy raft loads, we can exceed the timeout. When this happens, we hit a bug where the plan applier blocks waiting on the `indexCh` forever, and all schedulers will block in `Plan.Submit`. Closing the `indexCh` when the `asyncPlanWait` is done with it will prevent the deadlock without impacting correctness of the previous snapshot index. This changeset includes the a PoC failing test that works by injecting a large timeout into the state store. We need to turn this into a test we can run normally without breaking the state store before we can merge this PR.
This changeset is a proof-of-concept for a fault injection interface into the `FSM.Apply` function. This would allow us to introduce timeouts or errors in unit testing by adding a LogApplier implementation to a map of `interceptionAppliers`. This is similar to how we register LogAppliers for the enterprise FSM functions currently. Most interception appliers are expected to then call the normal applier directly. This was developed initially for #13407 but can't be used to reproduce that particular bug. But I'm opening this PR for further discussion about whether this is a worthwhile tool to have for testing otherwise.
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I'm going to close this out, as it doesn't really seem all that worthwhile except as a one-off experiment. |
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I'm going to lock this pull request because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active contributions. |
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This changeset is a proof-of-concept for a fault injection interface
into the
FSM.Applyfunction. This would allow us to introducetimeouts or errors in unit testing by adding a LogApplier
implementation to a map of
interceptionAppliers. This is similar tohow we register LogAppliers for the enterprise FSM functions
currently. Most interception appliers are expected to then call the
normal applier directly.
This was developed initially for #13407 but can't be used to reproduce
that particular bug. But I'm opening this PR for further discussion
about whether this is a worthwhile tool to have for testing otherwise.
(Once #13407 is merged I'll rebase this on
main)cc @lgfa29 @jazzyfresh