The library has a nice guide and two working examples, so I tried the local_federation example. To build the example, you need Rust compiler, cargo package manager, and git:

$ git clone https://github.com/LemmyNet/activitypub-federation-rust
$ cd activitypub-federation-rust
$ cargo run --example local_federation axum
[INFO  local_federation] Start with parameter `axum` or `actix-web` to select the webserver
[INFO  local_federation::axum::http] Listening with axum on localhost:8001
[INFO  local_federation::axum::http] Listening with axum on localhost:8002
[INFO  local_federation] Local instances started
[INFO  local_federation] Alpha user follows beta user via webfinger
[INFO  activitypub_federation::fetch] Fetching remote object http://localhost:8002/.well-known/webfinger?resource=acct:beta@localhost:8002
[INFO  activitypub_federation::fetch] Fetching remote object http://localhost:8002/beta
[INFO  activitypub_federation::fetch] Fetching remote object http://localhost:8001/alpha
[INFO  local_federation] Follow was successful
[INFO  local_federation] Beta sends a post to its followers
[INFO  local_federation] Alpha received post: Hello world!
[INFO  local_federation] Test completed

You may want to use network analizyer (e.g, wireshark) to see how it works under the hood.

GET /.well-known/webfinger?resource=acct:beta@localhost:8002 HTTP/1.1
accept: application/jrd+json
digest: SHA-256=[redacted]
signature: keyId="http://localhost:8001/#main-key",algorithm="hs2019",[...]
host: localhost:8002

HTTP/1.1 200 OK
content-type: application/json
content-length: 269
date: Sat, 03 Feb 2024 23:05:19 GMT

{
  "subject": "acct:beta@localhost:8002",
  "links": [
    {
      "rel": "http://webfinger.net/rel/profile-page",
      "type": "text/html",
      "href": "http://localhost:8002/beta",
      "template": null
    },
    {
      "rel": "self",
      "type": "application/activity+json",
      "href": "http://localhost:8002/beta",
      "template": null
    }
  ]
}

[...]
  • Remy Rose@lemmy.one
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    9 months ago

    I’ve run the example local federation code, but I didn’t know to use a network analyzer. Thanks! That should help a lot.

    If I happen to have some webhosting, domain name, and valid SSL cert, is there any harm in using that to learn live in-practice stuff with? Pretty sure I read somewhere about not doing that so as not to clutter up the fediverse with test posts or something.

        • nmtakeOP
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          9 months ago

          Hosting Lemmy instances on a localhost has these advantages: 1) no TLS required (right?), 2) can sniff the network traffic between the instances, 3) can change codes and settings of the all instances without asking to anyone, and more importantly, 4) no maintance cost. But if someone want to learn Web app deployment (TLS certs, hosting, etc.), your option would be a good idea.

          • maegul (he/they)@lemmy.mlM
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            9 months ago

            Agreed all around.

            But if someone want to learn Web app deployment (TLS certs, hosting, etc.), your option would be a good idea.

            I think for some they’d just get a real kick out of seeing their own thing federate. Actually “seeing it” happen might be motivation enough. Which I get completely, so I figure facilitating that for people, as well as running through the other web app stuff as you say (which again is worth “seeing happen” if you haven’t gone through it before).

    • maegul (he/they)@lemmy.mlM
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      9 months ago

      If I happen to have some webhosting, domain name, and valid SSL cert, is there any harm …

      Been wondering the same.

      The core devs run some test instances. It may be workable for any test instances we have to federate only with those (which may require the devs adding something to an allowlist or something). Anything we are running can of course federate with each other I suppose. Activity will be limited, but a little network we can poke may be all that’s necessary?

      @nutomic@lemmy.ml , if you don’t mind me bothering you, would something like this be at all feasible or useful? Otherwise, any thoughts on running test instances for ourselves and the load on the network?

  • maegul (he/they)@lemmy.mlM
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    9 months ago

    From the documentation linked in the OP:

    Creates two instances which run on localhost and federate with each other. This setup is ideal for quick development and well as automated tests.

    I didn’t realise there was an easy option for this. Thanks! I figured we’d have to put together such a local federation setup ourselves.

    Once you’re setup to make code changes to the local instances then you can poke around the system pretty well.

    • nmtakeOP
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      9 months ago

      Yeah, since the local_federation example doesn’t require complex setup, I think it would be a good entry point to learn ActivityPub and code reading.