[FS-1588] No proposals after deleting a subconversation #3123
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| msub <- embedClient (selectSubConversation convId subConvId) | ||
| for_ msub $ deleteAllProposals . cnvmlsGroupId . scMLSData |
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Why explicitly deleting the pending proposals? Essentially, this is buying Cassandra space and paying with users' time. I'd argue that users' time is more valuable. Also, the Cassandra records have a TTL and will be deleted eventually and they will not appear in a recreated subconversation, since the new subconversation's groupID is a different one than the one of the subconversation before. This is also demonstrated by your test which passes even without changes in business logic.
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Sorry for not seeing and commenting this when I checked this PR previously!
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Your reasoning is perfectly fine, but if we're to accept this argument, I'd prefer to hear arguments for the deleting a subconversation operation to be on a critical path, ideally backed by numbers showing this DB clean-up noticeably slows down the response time. We could let the proposals linger until they're garbage-collected, but to me this seems not so great.
I expect this delete DB statement to be deleting one or two records on average, and in rare case a handful of them. When this is put next to so many DB operations we do anyway in this endpoint handler, I'd argue the introduced time overhead is negligible.
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Can you raise this in the chat? I would argue that removing the records was not forgotten, but deliberately skipped. As to the critical path, ending a call should be done as quick as possible. What would you do if you hang up and nothing happens for a moment? We need a second opinion/review if you insist on cleaning up the non-user-facing database in exchange for user-facing latency.
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Since proposals have a TTL, there isn't much point to delete them, unless you really want them gone for semantic reasons. Note that deleting doesn't actually reclaim any space in cassandra, AFAIU.
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Ok, I'll revert the change in the application code. The test can stay as it doesn't hurt to assert there are no leftovers.
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Any further comments? |
This makes sure the database is cleaned up from leftover backend-generated remove proposals once a subconversation is deleted. Due to our test setup, this is not so straightforward to test, and doing a database test is not something we have been doing lately.
The test added by the PR just makes sure a recreated subconversation has no leftover proposals, but that holds because the recreated subconversation has a fresh group ID, hence fetching proposals for that new group ID yields no results anyway.
Tracked by https://wearezeta.atlassian.net/browse/FS-1588.
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