If you query the lemmy API, you get a ton of fun JSON data:

One thing interesting that I saw was huge lists of other federated servers in the federated_instances dictionary.

There’s three arrays in there:

  1. linked
  2. allowed
  3. blocked

What do each of these mean, and what impact does it have on the server when they’re set to some list of hosts or if they’re null?

  • poVoq@slrpnk.net
    4·
    1 year ago

    Linked just means they actively federate, allowed is a remnant from when the federation was strictly allow-list based in the early days (might be still possible to enable as a site admin), and blocked means exactly that.

    • maltfieldOP
      1·
      1 year ago

      Linked just means they actively federate

      What does “actively federate” mean? What does it mean to be “inactively federating”?

      What impact does it have on the user of these instances?

      • poVoq@slrpnk.net
        3·
        1 year ago

        The default is that any instance can federate, but only after a user actively requested that it is added to the list of linked instances. There is no central relay or so that tells an instance which other instances exists, so it needs to build up a list of known linked instances.

        • maltfieldOP
          1·
          1 year ago

          So if a user searches for a community on another instance, does that mean that the instance that they’re following is automatically added to the linked list or no?

          If so, does that happen when they subscribe or when they search?

          • poVoq@slrpnk.net
            2·
            1 year ago

            As far as I know, yes. I am not 100% sure if searching but not interacting is sufficient. But I think a reply is sufficient, not only actual subscriptions.

            • maltfieldOP
              1·
              1 year ago

              Interesting. So I guess that functionality is disabled when the admin has a non-null list set for allowed

  • maltfieldOP
    1·
    1 year ago

    See also

    Regarding “federation state”: You can have a blocklist, then Lemmy will federate with every instance except blocked ones. Or have an allowlist, then it will only federate with the allowed ones. If neither is set then it also federate with everything. Using allowlist and blocklist together doesnt make much sense, then it would only federate with allowed instances which are not in the blocklist.

    …but this doesn’t address what linked does

    • poVoq@slrpnk.net
      1·
      1 year ago

      Even with open federation an instance needs to know about other instances before they can actively push updates to them. This is what “linked” means.