Accurate vote counts?

[HugoGresse]

After last changes, the count count should be the real count as the DB does the increment, not a cloud function.
To DO

• setup 10 or so browser instances
• check that all session has different user id
• vote and unvote on many vote items randomly for 3 minutes
• assert vote count should not be higher than 10

[HugoGresse]

As to current deployed version it is still not.
I'm currently refactoring the votes to fix this issue.

[HugoGresse]

I've tried to fix this using "Distributed counter" aka writing to separate document from a collection but It did not solve the issue. (see #416)
Status:

• adding a lot of votes does not have any discrepancies between expected count and displayed counter after aggregation so this is good (in both production and with distributed counters)
• issue appear when adding and then removing the votes, in both solutions
• I did not test comments where this count be an issue but this has not been asserted.

The major issue for going to shard:

• additional cost : more queries everywhere
• more complexity overall
• "live" mode seems very hard to implement in this solution
• additional latency (really noticable) when displaying the vote count for every user due to additonal queries

So maybe the solution should be the "consolidate" the date on user request to fix the discrepancies. This seems more reasonable and the "dataConsolidation" branch has already been created though it's only a script and not a direct function callable by the user.

[HugoGresse]

Solution to investigate: https://firebase.google.com/products/extensions/firestore-counter/

[HugoGresse]

Other solution to investivate: FieldValue.increment https://firebase.google.com/docs/reference/js/firebase.firestore.FieldValue#increment