PostHog ingestion warning due to repeated identification of already identified user

[Johennes]

We're currently seeing around 2-3k daily ingestion warnings on PostHog.

Refused to merge already identified person foo-bar-foo into bla-bla-bla via an $identify or $create_alias call

Judging from the docs, these stem from attempting to call identify on an already identified user.

Browsing through the user list, many of them appear to be from Element Web so we should start the investigation here. The code already mentions a possible race condition but this isn't necessarily the root problem.

// Couldn't retrieve an analytics ID from user settings, so create one and set it on the server.
// Note there's a race condition here - if two devices do these steps at the same time, last write
// wins, and the first writer will send tracking with an ID that doesn't match the one on the server
// until the next time account data is refreshed and this function is called (most likely on next
// page load). This will happen pretty infrequently, so we can tolerate the possibility.

[Johennes]

@t3chguy could I ask you to take a look into this?

[laurencegill]

@Johennes we're still seeing these alerts FTR

https://posthog.element.io/data-management/ingestion-warnings

[t3chguy]

This looks like ios

https://posthog.element.io/person/fc7fa6a7-ccc1-4cfc-9973-03d0fffd463d#activeTab=featureFlags