Multicast discovery about smudge HOT 13 CLOSED

Hi Adirio,

I haven't spent much time looking at this project recently, but I've been looking for a reason to come back to it.

If it's something that you would find useful, I would be happy to implement it for you.

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That feature and IPv6 support, as I found while lookig at the code that only IPv4 support is provided, are two things that would be quite nice.

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from smudge.

Taking a look at multicast support now.

from smudge.

I'm wondering if multicast discovery should be left up to the application using smudge.

For example you could have 2 applications on a network that both use smudge to broadcast messages but should not connect to each others nodes as they do not share the same message model.

from smudge.

It seems appropriate for Smudge to do as part of the discovery process, but you're right that we need some way to distinguish between multiple collections that happen to share the same network.

Elasticsearch solves this problem by requiring that each cluster have a name/I'd set in each node by configuration, and announcements from nodes with a different name are simply ignored.

Thoughts?

from smudge.

That could work. That name should be replace foobar in the mdns example in this repo: https://github.com/hashicorp/mdns.

I also think that multicast discovery should be optional.

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I agree, discovery options should be configurable: the user has the option to introduce some seeds him/herself or use multicast discovery by providing a namespace.

from smudge.

Absolutely agree on all points.

I've almost got a working prototype together if you're interested (the issue6-multicast branch). Keep in mind that it's a feature-incomplete WIP though.

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membership.go lines 211-234:

func getMulticastAddress() string {
	if ipLen == net.IPv4len {
		if multicastAddress == "" {
			if ipLen == net.IPv6len {
				multicastAddress = defaultIPv6MulticastAddress
			} else if ipLen == net.IPv4len {
				multicastAddress = defaultIPv4MulticastAddress
			} else {
				logFatal("Failed to determine IPv4/IPv6")
			}
		}
	}

	return multicastAddress
}

You probably want to remove the outter if ipLen == net.IPv4len as it will not work properly for IPv6. You have the IP version check inside.

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Wait, what's that doing there? 😆

Good catch. I have no idea what I was thinking.

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I created PR #13 if you'd like to take a look at what I have.

If anybody wants to be a full-fledged collaborator so you can do proper code reviews, I'm certainly open to that as well. :)

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Merged #13.

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