[nexus] Remove SELECT FOR UPDATE, patch tests#6729
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smklein
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Oct 1, 2024
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| #[tokio::test] | ||
| async fn test_ensure_external_networking_works_with_good_target() { |
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I split this into a new test because it's really important that we actually perform a write after checking the target in the "bad case" below.
If we don't actually perform a write, then there is no circular dependency between transactions, and CockroachDB can logically re-order the "ensure resources" task before other operations that might write to the target, regardless of when it actually happened.
jgallagher
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Thanks for this. The comment in the reworked test is excellent.
Co-authored-by: John Gallagher <john@oxidecomputer.com>
…computer/omicron into select_for_serializability
andrewjstone
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Oct 1, 2024
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| // Release `ensure_resources_task` to finish. | ||
| return_on_completion.store(true, Ordering::SeqCst); | ||
| // == WHAT ORDERING DO WE EXPECT? |
andrewjstone
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Awesome stuff @smklein
hawkw
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Oct 2, 2024
Building off of: - #6229 (comment) - #6694 - https://github.com/oxidecomputer/sqldance This PR acknowledges that `SELECT FOR UPDATE` is a performance "optimization" in the situation where a blueprint's value is checked before performing a subsequent operation, as we do with setting network resources. It arguably could make performance worse in certain cases, as it locks out concurrent read operations from accessing the database. This PR removes the usage of `SELECT FOR UPDATE`, and significantly overhauls the `test_ensure_external_networking_bails_on_bad_target` test to account for the concurrent control that CockroachDB may be performing with respect to operation re-ordering. --------- Co-authored-by: John Gallagher <john@oxidecomputer.com>
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Building off of:
This PR acknowledges that
SELECT FOR UPDATEis a performance "optimization" in the situation where a blueprint's value is checked before performing a subsequent operation, as we do with setting network resources. It arguably could make performance worse in certain cases, as it locks out concurrent read operations from accessing the database.This PR removes the usage of
SELECT FOR UPDATE, and significantly overhauls thetest_ensure_external_networking_bails_on_bad_targettest to account for the concurrent control that CockroachDB may be performing with respect to operation re-ordering.