Some messages appear out of order

[vthriller]

Description

Some messages appear out of order, like on this screenshot from #mozilla_#servo:matrix.org:

The following are the snippets of said messages sources:

{
  "origin_server_ts": 1526498974801,
  "sender": "@mozilla_crowbot:matrix.org",
  …
  "age": 503879905,
  "unsigned": {
    "age": 503879905
  },
  …
}

{
  "origin_server_ts": 1526498969477,
  "sender": "@mozilla_jdm:matrix.org",
  …
  "age": 503885229,
  "unsigned": {
    "age": 503885229
  },
  …
}

And, obviously,

>>> 1526498974801 > 1526498969477
True
>>> 503879905 < 503885229
True

Steps to reproduce

• Join something.
• Accumulate a week or so of unread conversations.
• Read all the messages.
• Try again if failed to reproduce.

I'm able to replicate this by just looking for 20472, or 20632, or uluru/pull/8 in #mozilla_#servo:matrix.org's history (which, unfortunately, is not available for those who just joined the room).

Log: not sent

Version information

• Platform: web
• Browser: Firefox 57
• OS: Gentoo Linux
• URL: riot.im/app (0.15.2 at the time of writing this issue)

[t3chguy]

This could be caused by network delays and/or two servers disagreeing on the exact time. Its impossible to order by time in the server because that means you're trusting the time, and I could easily send an event from 1970 if I wanted to and you'd inject it to before the room even existed if you trusted me, its a common tradeoff in a publicly federated system

[lampholder]

As I understand it this is, as @t3chguy says, an unavoidable tradeoff and so I'm afraid not something that is going to be changed.

Good day,

We are seeing some messages appear out of order between the riot iOS app and the riot web client.

We are hosting our own synapse home server (0.99.5.1+stretch1) on Debian 9. We also host our own riot web client (v1.1.2).

The browser used to access the web client is firefox-esr (60.7.0esr-1~deb9u1), also running on Debian 9.

Our home server is configured not to federate (both in configuration and firewall settings). We only have a single home server, so there is no chance of two home servers disagreeing.

This seems to be a bug.

[turt2live]

1.1.2 has a bug which should be fixed in 1.2.0 (due to be released soon - there is a RC available).

I'm actually going to close this issue as there's nothing actionable on it.