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Message order in Matrix: right now, we are deliberately inconsistent

artificialworlds.net

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Re: Message order in Matrix: right now, we are deliberately inconsistent

#11

Post by danpalmer »

lmm wrote: post #8
danpalmer wrote: post #3

This is something that many chat apps get wrong and I'm not sure this article is moving in the right direction. The UX is fairly clear in my mind: 1. All up-to-date clients should be displaying the same message order. 2. A single client should not send messages in the wrong order. Yes a client may be out of date and therefore show something different, but once it becomes up to date it should be showing the same state…

> Additionally there are some clients that treat each message input by the user as a retriable thing in isolation, which is also clearly incorrect. If I send two messages and the first fails to go through, I almost certainly don't want to retry the second until the first has gone through, otherwise my client has literally sent out of order messages! I don't think that's clearly incorrect. If you sent two messages you…

Not at all. The separation of messages is part of communication, not me trying to game a network protocol. Maybe it's to emphasise a point, maybe it's to time a joke, maybe it's to send a photo and a text message separately.

Re: Message order in Matrix: right now, we are deliberately inconsistent

#12

Post by adastra22 »

winwang wrote: post #9
lmm wrote: post #8

Earlier quoted context omitted.

> Additionally there are some clients that treat each message input by the user as a retriable thing in isolation, which is also clearly incorrect. If I send two messages and the first fails to go through, I almost certainly don't want to retry the second until the first has gone through, otherwise my client has literally sent out of order messages! I don't think that's clearly incorrect. If you sent two messages you…

I break up my messages, as do many people.

Do you do so with the expectation that they might arrive out of order, or one fails?

Re: Message order in Matrix: right now, we are deliberately inconsistent

#13

Post by thaumasiotes »

lmm wrote: post #8
danpalmer wrote: post #3

This is something that many chat apps get wrong and I'm not sure this article is moving in the right direction. The UX is fairly clear in my mind: 1. All up-to-date clients should be displaying the same message order. 2. A single client should not send messages in the wrong order. Yes a client may be out of date and therefore show something different, but once it becomes up to date it should be showing the same state…

> Additionally there are some clients that treat each message input by the user as a retriable thing in isolation, which is also clearly incorrect. If I send two messages and the first fails to go through, I almost certainly don't want to retry the second until the first has gone through, otherwise my client has literally sent out of order messages! I don't think that's clearly incorrect. If you sent two messages you…

> If what you wanted to send was a single, multi-line message, surely you would have just done that?

No. danpalmer is correct; the break between messages is an integral part of the communication.

Re: Message order in Matrix: right now, we are deliberately inconsistent

#14

Post by throwaway14356 »

i had a hilarious argument with the significant other when my messages appeared a very lame response to messages i didn't receive.

i think the mental model should be what is most useful in court. if a netsplit occurs the state of the room doesn't exist anymore, conversation can continue but it should be a different room populated with working available clients. The main room can be restored and the missed convo can be a 3rd room

Re: Message order in Matrix: right now, we are deliberately inconsistent

#15

Post by adastra22 »

duskwuff wrote: post #7
thomastay wrote: post #4

Having dealt with this problem at work for several years now, I feel the pain of keeping different clients in sync - it's extremely difficult. Not sure if it's possible in Matrix, but consider having a message ID that increments by one on every message in a room. That lets the client know pretty quickly if there's a gap or a misordering. Not really getting this point though: The /sync API returns events in an order "…

What I think you're missing is that Matrix runs as a distributed system. There's no central authority to assign IDs to messages, and it's possible for a single group chat to run in a split-brain configuration if two homeservers lose connectivity to each other. When those homeservers reconnect, users connected to each one will see messages appear "in the past" which were sent by users on the other side of the split.

That makes the problem harder, but not impossible.

Re: Message order in Matrix: right now, we are deliberately inconsistent

#16

Post by shawnz »

danpalmer wrote: post #3

This is something that many chat apps get wrong and I'm not sure this article is moving in the right direction. The UX is fairly clear in my mind: 1. All up-to-date clients should be displaying the same message order. 2. A single client should not send messages in the wrong order. Yes a client may be out of date and therefore show something different, but once it becomes up to date it should be showing the same state…

How far back should you be able to amend history? What if a malicious client adds messages to a conversation that happened in the past? Imagine for example I'm at work and notice a critical mistake that I missed, and so I retroactively add messages to the old conversation to make it look like I'm not liable, should that be permitted by the protocol?

Re: Message order in Matrix: right now, we are deliberately inconsistent

#17

Post by glandium »

shawnz wrote: post #16
danpalmer wrote: post #3

This is something that many chat apps get wrong and I'm not sure this article is moving in the right direction. The UX is fairly clear in my mind: 1. All up-to-date clients should be displaying the same message order. 2. A single client should not send messages in the wrong order. Yes a client may be out of date and therefore show something different, but once it becomes up to date it should be showing the same state…

How far back should you be able to amend history? What if a malicious client adds messages to a conversation that happened in the past? Imagine for example I'm at work and notice a critical mistake that I missed, and so I retroactively add messages to the old conversation to make it look like I'm not liable, should that be permitted by the protocol?

Matrix allow to edit weeks old messages, already.

Re: Message order in Matrix: right now, we are deliberately inconsistent

#18

Post by thomastay »

duskwuff wrote: post #7
thomastay wrote: post #4

Having dealt with this problem at work for several years now, I feel the pain of keeping different clients in sync - it's extremely difficult. Not sure if it's possible in Matrix, but consider having a message ID that increments by one on every message in a room. That lets the client know pretty quickly if there's a gap or a misordering. Not really getting this point though: The /sync API returns events in an order "…

What I think you're missing is that Matrix runs as a distributed system. There's no central authority to assign IDs to messages, and it's possible for a single group chat to run in a split-brain configuration if two homeservers lose connectivity to each other. When those homeservers reconnect, users connected to each one will see messages appear "in the past" which were sent by users on the other side of the split.

yeah, having eventual consistency for messages across homeservers makes the work on the client harder. I guess they just have to accept that messages will "appear in the past" as you said.

But at least for messages sent within the same homeserver, I would think that those two apis should return the same data

Re: Message order in Matrix: right now, we are deliberately inconsistent

#19

Post by shawnz »

glandium wrote: post #17
shawnz wrote: post #16

Earlier quoted context omitted.

How far back should you be able to amend history? What if a malicious client adds messages to a conversation that happened in the past? Imagine for example I'm at work and notice a critical mistake that I missed, and so I retroactively add messages to the old conversation to make it look like I'm not liable, should that be permitted by the protocol?

Matrix allow to edit weeks old messages, already.

But there's a flag which indicates they've been edited and you can see the edit history, right? So that's not useful for this scenario.

Re: Message order in Matrix: right now, we are deliberately inconsistent

#20

Post by thomastay »

shawnz wrote: post #16
danpalmer wrote: post #3

This is something that many chat apps get wrong and I'm not sure this article is moving in the right direction. The UX is fairly clear in my mind: 1. All up-to-date clients should be displaying the same message order. 2. A single client should not send messages in the wrong order. Yes a client may be out of date and therefore show something different, but once it becomes up to date it should be showing the same state…

How far back should you be able to amend history? What if a malicious client adds messages to a conversation that happened in the past? Imagine for example I'm at work and notice a critical mistake that I missed, and so I retroactively add messages to the old conversation to make it look like I'm not liable, should that be permitted by the protocol?

Obv it depends, but one way to "solve" this it is to show an edit history, or at least the latest edit timestamp along with some visual indicator that the message was edited recently
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