fleet/changes/16562-policy_stats-lock
Victor Lyuboslavsky 9c714c544d
Optimized policy_stats updates to NOT lock the policy_membership table (#18720)
#16562

Optimized policy_stats updates to NOT lock the policy_membership table.
This should improve deployment performance with many global policies and
team hosts.

The original implementation that used INSERT ... SELECT (SELECT
COUNT(*)) ... caused performance issues. Given 50 global policies, 10
teams, and 10,000 hosts per team, the INSERT query took 30-60 seconds to
complete. Since it was an INSERT query, it blocked other hosts from
updating their policy results in policy_membership.

Now, we separate the INSERT from the SELECT, since SELECT by itself does
not block other hosts from updating their policy results. In addition,
we process one global policy at a time, which reduces the time to
complete the SELECT query to <2 seconds, and limits the memory usage. We
are not using a transaction to reduce locks. This means that INSERT may
fail if the policy was deleted by a parallel process. Also, the INSERT
may overwrite a clearing of the stats. This is acceptable, since these
are very rare cases. We log and proceed in that case.


# Checklist for submitter

If some of the following don't apply, delete the relevant line.

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- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
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files](https://fleetdm.com/docs/contributing/committing-changes#changes-files)
for more information.
- [x] Added/updated tests
- [x] Manual QA for all new/changed functionality
2024-05-06 09:48:37 -05:00

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Optimized policy_stats updates to NOT lock the policy_membership table. This should improve performance on deployments with a large number of global policies and team hosts.