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[lib] Check the timestamps when adding thread members
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Authored by tomek on Sep 2 2024, 1:36 AM.
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Details

Summary

Check the timestamp and don't update the membership when the timestamp is more recent than the operation.

https://linear.app/comm/issue/ENG-9113/update-addmembersspec

Depends on D13215

Test Plan

Tested mostly in combination with the rest of the stack.
Check if the timestamp gets properly updated: create an operation at T+1 time which adds u1, u2, and u3, and an operation at T which adds u3, and u4. The timestamps should be T+1, T+1, T+1, T respectively. Also, the membership array should contain all the members without any repetition.

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Event Timeline

tomek requested review of this revision.Sep 2 2024, 1:57 AM
lib/shared/dm-ops/add-members-spec.js
86 ↗(On Diff #43823)

We're assuming the oldest possible update time.

inka added inline comments.
lib/shared/dm-ops/add-members-spec.js
90–92 ↗(On Diff #43833)
This revision is now accepted and ready to land.Sep 3 2024, 3:33 AM
lib/shared/dm-ops/add-members-spec.js
90–92 ↗(On Diff #43833)

My proposition will break in case the equality comes from the if above being run - we won't add the user to members. But we should still handle the case where this timestamp collision is a result of two separate requests

lib/shared/dm-ops/add-members-spec.js
90–92 ↗(On Diff #43833)
lib/shared/dm-ops/add-members-spec.js
94–97

Why do we bump the timestamp even if we continue on line 100 below?

114–121

If no changes end up being applied, is there a way we can skip this update, instead of propagating an empty update?

lib/shared/dm-ops/add-members-spec.js
94–97

It is to handle the following scenario:

  1. We receive an operation about a user being added at time T
  2. We don't receive an operation about the user leaving the thread at T+1
  3. We receive an operation about the user being added at T+2

We want to keep the user in the membership table, but we should update the timestamp so that when we receive the operation from T+1 we don't remove the user.

114–121

Obviously, there is, but the case where no updates were made is a relly unlikely edge case, and don't think is worth introducing. If you feel strongly, I can add that (and review all the specs to check whether we can skip updates also there). Created https://linear.app/comm/issue/ENG-9232/consider-skipping-creating-updates-when-there-are-no-changes-to-a to track.

lib/shared/dm-ops/add-members-spec.js
94–97

Thanks for explaining!

114–121

Appreciate the explanation. I don't feel strongly, and didn't have the context that it's unlikely. I don't feel strongly, so I'll go ahead and cancel the task you created – sorry for the churn!