Issues with 'gossip-chat' Example

[moconn68]

Hello,

I've encountered a couple of issues with the 'gossip-chat' example from the iroh docs. I've tried troubleshooting a bit with LLDB, but wasn't able to figure out where the problems were.

• If a peer sends the same message content as what they sent for their first message after joining, it will not be sent.
• When peer n (where n > 2) joins, the new peer will not be able to see the nicknames of the other peers 0..n-1. This is true for all other new peers thereafter

Please let me know if any additional information is needed to help reproduce and/or debug the issue!

[matheus23]

If a peer sends the same message content as what they sent for their first message after joining, it will not be sent.

Yeah - this is a known issue :) We should really fix this.
The reason for it is how iroh-gossip works. Since you're broadcasting messages in a swarm, you might get the same message from the same peer via different paths (e.g. the message originated at peer A, then which told peer B and C about it, peer B told you about it and later C tells you about it, too), so internally iroh-gossip de-duplicates messages and stops the rebroadcasting when it detects that it would send the same message twice.
This means you can't send the exact same message twice. What you need to do is either add a timestamp or some nonce.
(We don't want to make this built-in, because having access to "just send bytes" is nice to have, no need for additional overhead in some cases.)

When peer n (where n > 2) joins, the new peer will not be able to see the nicknames of the other peers 0..n-1. This is true for all other new peers thereafter

Yeah this is interesting, and might be due to the way the gossip chat example protocol works, and, again, might have to do with message deduplication.

Let me know if you're interested in contributing a PR that simply adds a randomly-generated 16-byte nonce to each message, to make sure rebroadcasting works. We'll fix it either way, it might just take us a little longer until we come around to it.

Thank you for the detailed look into this! :)

[matheus23]

Uuuuhm actually nevermind, someone opened a PR already: #60

😅

[moconn68]

Ah that's awesome, thanks for sharing! Sounds like this would most definitely solve the first problem, and also perhaps the second one too. I'll try to test it out this weekend

Edit: one additional comment here - looking at the example code from the PR, it looks to be somewhat different from the one in the docs. Is there somewhere else that this example needs to be updated?

[matheus23]

Is there somewhere else that this example needs to be updated?

The code for the page linked is pulled from github here: https://github.com/n0-computer/iroh.computer/blob/main/src/app/docs/examples/gossip-chat/page.mdx

[moconn68]

Thanks @matheus23. I just tested the docs example with the nonce changes, and the first issue is resolved. I can open up a PR in the iroh.computer repository to update that example code to mirror the changes in #60 mentioned earlier.

Even with the nonce, the second issue still exists so I think that is separate. I'm not sure if this issue is something that you'd consider to be in-scope for the example, but if so I can try and keep digging at it and put up a PR if I find a solution. Granted, playing with this example is my first time working with iroh so I'm very much a newbie, but I'd be happy to take a crack at it

[matheus23]

Please have a go! If you need some guidance, feel free to hop into our discord and we can also chat synchronously about things that come up, if you want.