No updates on chat join

[megagosha]

The problem is that the bot does not receive any updates when user joins my supergroup (> 20k users). I used another smaller group for testing and everything was fine there.

In BotApi doc it says that for getUpdates method "chat_member" should be specified in allowed_updates field in order to receive this update type.

Am I doing something wrong or this is expected behaviour for supergroup of this size?

[dani0854]

This bot uses OnUserJoined events, which are triggered by join service messages (public messages in chat saying user joined). I had a problem that in some cases users were able to join group without triggering a service message. And telegram support said that service message on user join is not guarantied, and specific cases where it does not exist are undefined.

So I had to rewrite the bot to use OnChatMember instead, which is independent on that.
Unfortunately, I did change a lot of other things, making it hard to cherry-pick those specific changes to merge them from my fork back to here.