investigate invitations processing: event for Europe only got about 500 invites

Summary

I created an event for Europe. (https://foodsharing.de/?page=event&id=16720) The day after I launched it, there were about 600 invites sent. I changed the region to Deutschland - more than 6000 invites were sent. I changed it back to Europe - less invites than before with Germany, weirdly, but still in the thousands. After the event in question was changed some more around by others, 78197 were sent. All the time the 'invite all regions below' box was checked.

Steps to reproduce

Create an event for a higher tier (say: Europe). Take a note, how many invites got sent. Change the event so, that a tier lower gets invited (say: Germany or Berlin). Take a note, how many invites got sent, compare.

What is the current bug behavior?

The higher tier has less invites, weirdly.

What is the expected correct behavior?

The highest tier should reach all FS instantly.

Relevant error messages and/or screenshots

https://yunity.slack.com/archives/C1T1ZM9A4/p1598017666010400?thread_ts=1596991986.386700&cid=C1T1ZM9A4

Possible fixes

Alex said, it might be related to !1285 (merged) and we might need some kind of asynchronous processing.

(If you can, link to the line of code that might be responsible for the problem)

Edited by Jonathan Steinker