Provable server-side caching bug with Nitro

[spotlightishere]

This issue was also sent via support (message 3910645) but since it's API related it was suggested to also send here.

Seemingly prerequisites for reproduction:

• Gifted nitro cancelling before grace period with billing
• Open client over night with old discrim cached and no web socket reconnect

Timeline:

• I cancelled my Nitro gift from Hype Squad a few hours before actual Nitro was supposed to end. This soon after reset my discrim from #6201 to #1270. I had kept my Discord client open over night.
• Bots received an update for my gif avatar/discrim randomising twice. Namely at 2019-01-20 at 01:15 CST, once more at 2019-01-20 at 01:20 CST.
• Avatar alone was sent twice at 2019-01-20 at 08:59 CST the same day. I figured this might’ve been some type of rollback that occurred and that all would be fine.
• People began tagging me as @Snoot 🐾#6201#1270. I figured cache hadn’t gone through.
• Without member updates being sent to bots, the discrim 6201 began to show for others regardless of cache/old connection.

Requests over REST showed my discrim as 1270, as expected. e.g the profile endpoint. Messages received over the gateway (i.e message receive namely) had 6209 and gave the effect of my discrim repeatedly changing.

This continued and was attempted to be debugged as a client issue until everyone active in Discord Bots at the time was able to reproduce. While debugging, the client signed me out. Upon reauthentication, an event was sent out with my discrim changing again and for a select few servers avatar alone changed.

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Proof of this bug not being (or at least not single) user error

- The following screenshot of it happening to a client was taken by stupid cat in the recommended unofficial Discord Bots server. You can also see it using the previous GIF avatar despite that being changed to my own client.  - The following screenshot of the quick switcher being confused was taken by Erisa in the same server.  You can find many examples of clients breaking over mentions rapidly changing throughout Discord Bots, such as `110373943822540800-536774356412661760` and that entire block of messages. The mentioned support ticket has more linkable proof to this.

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As of right now, it appears to have stopped. As mentioned: after my known last connection ending, a final event was sent out to some shards of avatar update and discriminator changing.

The REST API and websocket gateway continue to agree that 1270 is now the proper discrim.

https://canary.discordapp.com/api/v6/users/239809536012058625

{"username": "Snoot \ud83d\udc3e", "discriminator": "1270", "id": "239809536012058625", "avatar": "9dc57404a14c9fc7492ebde1d091c0a9”}

https://canary.discordapp.com/api/v6/channels/514936074967973893/messages/536777305733726208

{ […] "author": {"username": "Snoot \ud83d\udc3e", "discriminator": "1270", "id": "239809536012058625", "avatar": "9dc57404a14c9fc7492ebde1d091c0a9"}, [..] }

[night]

I cancelled my Nitro gift from Hype Squad a few hours before actual Nitro was supposed to end. This soon after reset my discrim from #6201 to #1270. I had kept my Discord client open over night.

was your subscription status past due? if not, the "cancel" just marks it to cancel at period end. if it is the latter, then my following comments make sense.

Bots received an update for my gif avatar/discrim randomising twice. Namely at 2019-01-20 at 01:15 CST, once more at 2019-01-20 at 01:20 CST.

i would suspect based on this timeline that the removal failed due to an internal error (likely the user database queries succeeded but the billing database write failed) and it retried 5 minutes later and succeeded. queries are highly elevated over the past couple days due to subscription renewals for the hypesquad promotion, so there is a slightly increased error rate as a result.

Avatar alone was sent twice at 2019-01-20 at 08:59 CST the same day. I figured this might’ve been some type of rollback that occurred and that all would be fine.

I'm not sure I understand what you mean. Avatar updates, if there are any, would have been at the exact same time as the above.

In general, a lot of our client/gateway is eventually consistent and relies on dispatched events for updating state. It looks like we are not dispatching a user update when we revoke your perks, which is likely the cause for the inconsistency here. I'll see if we can address that this week. Refreshing your client is the easiest fix to this problem for now.

[spotlightishere]

Indeed, the subscription had been cancelled before the grace period would've kicked in. Refreshing (or in my case, logging back in) fixed it.

I personally cannot verify the avatar updates, only that separate bots had them sent twice at the same time. Perhaps that was their issue indeed, was just noted to show how odd it is. Best to ignore that part. Hope it's not too much of a hassle to track down for others.

[night]

this is fixed