| 16 Jul 2025 |
 Zhaofeng Li | In reply to @k900:0upti.me
Because you need to talk to another server to join a room * let's say the newly-joined homeserver can talk to all homeservers including B and matrix.org (both blocked by A) except for A which is down forever | 20:19:55 |
 K900 | Like fundamentally Matrix room state is not consensus, it's CRDT | 20:21:49 |
| K900 | So different participants seeing different states is expected | 20:22:02 |
| K900 | And ideally everything gets reconciled in the end | 20:22:17 |
| Zhaofeng Li | In reply to @k900:0upti.me
Like fundamentally Matrix room state is not consensus, it's CRDT right, it makes sense, but practically it's... unproductive? | 20:22:37 |
| K900 | It is | 20:23:44 |
| Zhaofeng Li | any participating homeserver can become load-bearing and make the room unusable (for many common use cases) | 20:24:35 |
| K900 | I don't think there's a solution for achieving this that is actually good | 20:24:57 |
| K900 | Any sort of consensus algorithm is susceptible to 51% attacks | 20:25:16 |
| K900 | And CRDTs are susceptible to splits | 20:25:28 |
 magic_rb | 51% is a fun one, ive long been fascinates by distributed systems, but any system you come up with which is based on consensus can be taken over by the 51% thing | 20:30:40 |
| K900 | The only thing I can think of is doing some kind of roughtime thing | 20:31:15 |
| magic_rb | Roughtime? | 20:31:34 |
| K900 | Where you have an external trusted timing oracle | 20:31:34 |
| K900 | Or five | 20:31:39 |
| magic_rb | "Trusted" and "distributed" dont go together :P | 20:31:59 |
| K900 | But that's arguably a single point of failure | 20:32:00 |
| magic_rb | (So is matrix.org) | 20:32:12 |
| K900 | In reply to @magic_rb:matrix.redalder.org
Roughtime? https://roughtime.googlesource.com/roughtime | 20:32:13 |
| magic_rb | Oh nice, didnt know rhat | 20:33:51 |
| K900 | But you still need to agree on the set of roughtime servers to trust | 20:34:32 |
| K900 | Or include a giant pile of receipts in every state event just in case someone in the federation trusts that particular server | 20:35:21 |
| magic_rb | Distributed systems are hard :( | 20:38:06 |
 c-x-berger | http://scholar.harvard.edu/files/mickens/files/thesaddestmoment.pdf | 20:38:22 |
| c-x-berger | * for further reading http://scholar.harvard.edu/files/mickens/files/thesaddestmoment.pdf | 20:38:37 |
 emily | https://developers.cloudflare.com/time-services/roughtime/ fwiw | 20:55:30 |
| emily | cloudflare kinda adopted the protocol from google at this point | 20:55:43 |
| emily | they do run a server | 20:55:46 |
| Zhaofeng Li | In reply to @k900:0upti.me
But you still need to agree on the set of roughtime servers to trust So the answer is still some level of centralization then. Maybe this can be done on the room-level, where the room creator decides on a set of homeservers that maintain the canonical room state | 21:03:10 |
 Charles | that is hilarious, thank you for sharing | 23:22:38 |
