mDNS's new implementation doesn't perform as well

[MichaelMure]

Sorry, no hard number to provide other than "upgrading to the new implementation makes my test fails all over the place, randomly.

I have a series of go test for my project that simulate locally the interactions of a series of services. Those test rely on mDNS for local discovery.

Until now I had a simple time.Sleep() to give this discovery some time to connect, everything was fine. While updating to a more recent go-libp2p, I changed my code to use the new mDNS implementation, resulting in broken tests. I changed my time.Sleep() by something smarter that wait until the discovery worked, up to a minute, but that doesn't seems to be enough.

It seems to me that often the discovery is slower, and sometimes never succeed in a 1 minute period.

Is that something to expect? Is this a bug?

[marten-seemann]

That's not expected, and might very well be a bug.

Are you still using the old mDNS in parallel? We might have another issue with one of the two implementations that might or might not be related: ipfs/kubo#8695.

In general, mDNS discovery should be fast. Nodes that join the network will query their peers, so they should receive a response very quickly. Have you tried running WireShark to see what's going on on the wire?

[MichaelMure]

Are you still using the old mDNS in parallel?

Not in parallel but when I replaced it with mdns_legacy everything worked again.

Have you tried running WireShark to see what's going on on the wire?

No. I can give it a try but I'm familiar at all with what mDNS should looks like.

[MichaelMure]

I tried to wireshard a bit. While with the legacy implementation it does show up in wireshark on localhost, the new implementation traffic either doesn't show up or is not recognized properly.

[BigLep]

2022-04-27 conversation: wireshark-level view is needed here. We're not sure why the new mdns is not showing up for @MichaelMure . This is likely ~.5 day of work to debug. We've downgraded to P2 as there are other peer discovery mechanisms we rely on.

[schomatis]

Assigning myself.

[schomatis]

@MichaelMure Could you share your tests or any small reproduction of your issue, please?

[schomatis]

@marten-seemann I'm blocking this on "need more input from author" as there's little to do without the failing test or something to reproduce the issue with. I have nothing to work on and the other issue is being diagnosed independently.