@freemo or anyone: I'm trying to find out how connected the graph of fediverse nodes is. For instance, if it's fully connected (every node connected to every other), that might imply a scalability limit to the number of nodes.

I guess another way of framing the question is whether two nodes A and B are necessarily directly connected because a user in node A follows a user in node B.

#fediverse #graph #connectedness #topology #scalability

@underlap
It is not fully connected. Nodes federate with eachother whenever a user from one node follows a user from another. Only federated servers that share atleast one pair of mutual followers sync up but in that case thry sync up all users and all users from one server will appear in the federated timeline of the other.

You also have servers that operate whitelists or blacklists that block other servers.

@freemo @zpartacoos Very interesting. So the graph of nodes is "induced" by the graph of user follows.

So a node with a larger number of users would probably need to connect to correspondingly more other nodes because of the disparate social networks of its users. On the other hand, small nodes with, say, a hundred users who each follow less than a hundred others would only need to connect to at most 10k other nodes, and probably a lot less. (If there were billions of users, I think discovery would become a problem unless there are some nodes with very many users.)

@underlap
There are relays to help with discovery.
@zpartacoos

@freemo I can't find a definition of an ActivityPub relay - just various lists of them and nothing in the spec. Do you have a good reference, please?
@zpartacoos

#activitypub #relay #mastodon