Michał Chojnowski 379f23d854 cache_algorithm_test: harden against stats being confused by background activity ...

Cache stats are global, so there's no good way to reliably
verify that e.g. a given read causes 0 cache misses,
because something done by Scylla in a background can trigger a cache miss.

This can cause the test to fail spuriously.

With how the test framework and the cache are designed, there's probably
no good way to test this properly. It would require ensuring that cache
stats are per-read, or at least per-table, and that Scylla's background
activity doesn't cause enough memory pressure to evict the tested rows.

This patch tries to deal with the flakiness without deleting the test
altogether by letting it retry after a failure if it notices that it
can be explained by a read which wasn't done by the test.
(Though, if the test can't be written well, maybe it just shouldn't be written...)

(cherry picked from commit 6caaead4ac)

2025-01-08 11:48:23 +01:00

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