Add locking to more safely delete state groups: Part 1 #18107
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Currently we don't really have anything that stops us from deleting state groups when an in-flight event references it. This is a fairly rare race currently, but we want to be able to more aggresively delete state groups so it is important to address this to ensure that the database remains valid. See the class docstring of the new data store for an explanation for how this works.
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devonh
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| transaction we recheck `state_groups_pending_deletion` table again and see | ||
| that it exists and so continue with the deletion. To prevent this from | ||
| happening we add a `sequence_number` column to | ||
| `state_groups_pending_deletion`, and during ensure that for a state group |
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this should be "and during deletion"
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| # TODO: Clear from `state_groups_persisting` any holdovers from previous | ||
| # running instance. |
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I'm assuming this will be in Part 2 of the state groups deletion PR series?
| groups that we want to delete. | ||
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| To handle this, we take two approaches. First, before we persist any event | ||
| we ensure that the state groups still exist and mark in the |
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| we ensure that the state groups still exist and mark in the | |
| we ensure that the state group still exists and mark in the |
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| -- The `id` column *must* be updated whenever a state group may have become | ||
| -- referenced. |
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Not sure what this is referring to.
Maybe it should just be removed.
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| if state_groups - existing_state_groups: | ||
| return state_groups - existing_state_groups |
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Would be better to only do this set manipulation once.
Suggested change
| if state_groups - existing_state_groups: | |
| return state_groups - existing_state_groups | |
| missing_state_groups = state_groups - existing_state_groups | |
| if missing_state_groups: | |
| return missing_state_groups |
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| can_be_deleted = ready_to_be_deleted - not_ready_to_be_deleted | ||
| if not_ready_to_be_deleted: | ||
| # If there are any state groups that aren't ready to be persisted, |
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| # If there are any state groups that aren't ready to be persisted, | |
| # If there are any state groups that aren't ready to be deleted, |
| @@ -19,7 +19,7 @@ | |||
| # | |||
| # | |||
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| SCHEMA_VERSION = 88 # remember to update the list below when updating | |||
| SCHEMA_VERSION = 89 # remember to update the list below when updating | |||
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Update the list below with an entry about adding tables for state group deletion.
| self.assertFalse(can_be_deleted) | ||
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| def test_deletion_error_during_persistence(self) -> None: | ||
| """Test that state groups remain marked as for deletion if persisting |
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| """Test that state groups remain marked as for deletion if persisting | |
| """Test that state groups remain marked as pending deletion if persisting |
| self.assertTrue(can_be_deleted) | ||
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| def test_race_between_check_and_insert(self) -> None: | ||
| """Check that we correctly handle the race where we got to delete a |
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| """Check that we correctly handle the race where we got to delete a | |
| """Check that we correctly handle the race where we go to delete a |
| ) | ||
| ) | ||
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| # We shouldn't be able to delete the state group as not enough time as passed |
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Suggested change
| # We shouldn't be able to delete the state group as not enough time as passed | |
| # We shouldn't be able to delete the state group as not enough time has passed |
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Currently we don't really have anything that stops us from deleting state groups when an in-flight event references it. This is a fairly rare race currently, but we want to be able to more aggressively delete state groups so it is important to address this to ensure that the database remains valid.
This implements the locking, but doesn't actually use it.
See the class docstring of the new data store for an explanation for how this works.