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Top-level
 Now you may be saying, "Christine, this is really unfair, because you're looking at ActivityPub servers which are only dealing with a small amount of the network, what if it were an ActivityPub mega-node? What are the costs THEN huh?" and "What if we hosted just PART of ATProto?" What then INDEED 459 comments
Remember the directive that Bluesky was given: develop a decentralized protocol which Twitter can adopt. That informs a lot of things, and has meant that Bluesky was really very ready for this moment! If you're an ex-X-Twitter user then by god, you're going to be amazed! It's just like Twitter! This informs some other things: But here's the other thing. People have trouble with the fediverse! All those decentralization decisions get in the way, my god, you've got to choose a server, search doesn't work well (actually it could but it's a cultural thing, different topic), and worst of all: Sometimes you DON'T SEE REPLIES! Actually all these critiques of the fediverse are TRUE, these are known challenges, and actually it's not really so bad, but it could be better, and at any rate, Bluesky made a major decision to simplify a lot for new users, and they have. Things seem to just work for people! Incredible! The thing you often get seen thrown around is "it's amazing, I had no idea a decentralized protocol could just work like that! How on earth did they solve that in a decentralized system and so FAST too!" It's simple: all those things "just work" because Bluesky is centralized. Now yes, they are using decentralized techniques. Remember when I said content-addressed storage is a good idea and the fediverse should do it too? IT IS! (And as I also said, it's actually fully possible for the fediverse to do, more on that later.) But the reality is, it's still *centralized* In every meaningful way from a power dynamics perspective *EXCEPT* the category of "credible exit" (which I am saying and agreeing is a good idea!) Bluesky is centralized. MAYBE another big corporation could come along and host all this stuff but that's adding a Bing to our Google Yes, you can host your own PDS. You can also host your own blog. But try hosting your own PDS and NOT hosting a relay or AppView and you can't do much. Blogs are decentralized, Google is not. We're getting to the point where we get to why I'm so damn frustrated about this and have been biting my tongue until it nearly comes detached from my mouth: users THINK Bluesky is decentralized because they're TOLD Bluesky is decentralized AUGH! *That's* what drives me nuts. @cwebber if theres one frustration i have trying to mature a tech thing the last few years its that "maybe this could work in the future" seems to be a much much bigger draw for people than "this is actually working now and we can use it if only we do X". it suckssss. like imagine if mastodon was only mastodon.social lol Here's an example of this problem in action fry69: "The working search box was the second thing that impressed me on Bluesky, I thought that was not possible with a decentralized model" Sorry fry sixty-nine I regret to inform you the reason search works so well is that it's centralized! THAT'S WHY So hold on, let me set some terms for "decentralization" and "federation" that I think are reasonable. > Decentralization: the result of a system that diffuses power throughout its structure, so that no node holds particular power at the center. Pretty reasonable. Do you agree? I hope so! Okay how about "federation" now because this is a *technical term* that the *fediverse has established* and I'm kinda PO'ed about the goalposts being moved on this one. A lot of people coming to Bluesky have never heard of "federation" before in a social network so listen up this is important! Here's my definition of federation: > Federation: a technical approach to communication architecture which achieves decentralization by many independent nodes cooperating and communicating to be a unified whole, with no node holding more power than the responsibility or communication of its parts. Now historically, federation has been achieved on the fediverse via "message passing". Actually, this is to the degree where I just always associated message passing with federation, but really, federation is about the distribution of power, creating an abstract whole in a sea of autonomy. Maybe there is another way to achieve federation, but it's about the power dynamics. It's a technical immersion of power dynamics, the flow and interchange of cooperation between many parts. So you may say, well, doesn't ATProto have that? After all, messages flow through the different parts! ActivityPub, as it turns out, follows the actor model of computation. Okay, many people implementing the fediverse don't know about the actor model aspect of ActivityPub but I am here to tell YOU, dear reader, that it is an important thing, not a detail I'll take one more note about federation which is that often time the message passing mechanism of the fediverse is often called "federation", but theoretically another mechanism could exist, but I'm actually not so sure of that. There's a reason the actor model and the lambda calculus are undying Oh god Christine said "the lambda calculus" did you know she's into lisp and functional programming, what's she going to talk about next monads?!?! I am not going to talk about monads. Not TODAY But we do need to get a better architectural idea of how these systems work because it matters a lot!  @cwebber your spooky Halloween name next year should be Christine "Leibniz"-Webber So let me introduce two models of communication which we can use to analyze these two systems. It's important! - Fediverse/ActivityPub: "message passing" Okay, cool, terms established, let's talk about them and why they matter because they matter A LOT "Message passing" is what ActivityPub uses. It's "like email", people say, and that's true. Actually it's even a lot like physical mail. You write a letter, you say where it should go, it gets delivered to your house. Message passing. The world runs on it. Now I can use message passing to send a message to you *directly* and indeed, that's "like email". For one-to-one correspondence, that's enough. But it's not enough for a followers/following type mechanism. But we can build it on top! Thank *you* computational abstractions! On top of "message passing" we will build "publish-subscribe" as a second-layer abstraction "Your ideas are interesting and I'd like to subscribe to your newsletter." You send me a letter saying you'd like to hear the things I have to say, okay, you're part of the reader list. That's how it works. On top of that we can build even more abstractions and the net result is that this is how federation works in pretty much every "federated" system I know. ActivityPub does some extra work to help you see replies on a thread, think "letters to the editor". This is a bit lossy sometimes though It's true that sometimes users click over to a thread and see some replies but not all on their instance's UI. There's things that could be done to improve it, but it's sometimes mildly confusing, but not so bad, and you can click over typically to see whatever else is happening, and people learn to I actually think this is improvable but I mostly don't care because this isn't as big a complaint as people tend to think it is on the fediverse, the other concerns like "what instance do I pick" tend to be bigger and "oh no my server went down" That can be improved, we'll talk about that later So okay, the federation is "message passing" and like email, or physical mail. You have an idea how it works. Now we need to get to that other thing, a "shared heap" architecture. What on earth does that mean? If "message passing" is like "mail comes to your house", a "shared heap" system works differently In a "shared heap" system, all the mail gets dumped at the post office, and in the most naive version, you go over there and read through every single piece of mail to see which one is relevant to you There is no "directed delivery" in a "shared heap" system, which means you are stuck with two things: either a "god's eye view" (Bluesky) or "even lossier about replies than ActivityPub" (Secure Scuttlebutt/Nostr) The Bluesky approach to the "shared heap" is that *everything* goes into the big, centralized shared heap. Bluesky takes a "god's eye" view: it knows everything, and so knows what all your replies are, and can give you perfect search. Secure Scuttlebutt / Nostr... well long story. Lossier, I'll say You can imagine the physical world version of "message passing" already because you already live in this world. Messages come to your house or apartment building or whatever For Bluesky's "shared heap" architecture, you'd have to build a whole addition to your house for everyone's mail That's exactly why running a Relay or AppView is expensive: you're building an addition to your house for all the world's mail. Eeep! That ain't cheap. That's why I'm saying: decentralization also means the ability to *scale down*. Look, I know that I've been hitting this nail on the head for a while but: the web is open, blogs are open, but Google isn't open But you could run your own Google, in theory. You could index the web. So why aren't you? Ah yeah. Same thing here. That's what I mean, that's why it's centralized Now as I have said, this is a *design decision*. And remember: most users of Bluesky really *don't care*. Decentralization is not their focus, they're trying to get the hell off the nazi hellscape that Musk's toxic reign of Twitter has become. Bluesky's architecture, actually, is great for them.  @cwebber I just saw this one comment, and then... clicked it and started scrolling up. Woo, time to read.  @cwebber My gourds, this thread has been a wild, insightful ride so far!  @cwebber I want to be able to speak intelligently enough on the subject, but I only learned enough about Bluesky/ATProto to know that I wasn't interested in using it. Do you think it's worth understanding to be able to explain to people? And/or is there a good brief explainer somewhere? @cwebber I have kind of an axe to grind about "decentralized" systems that are really centralized organizations using some decentralized tech. People look at the protocols and cables to evaluate centralization, but what really matters are the wider trust relationships that are a layer even below those. @cwebber Dropping in mid-thread just to thank you for it! Helps me understand things. :)  @cwebber PDSes are like your house. Relays are like telecoms.  @cwebber An analogy I've used with some folks is to imagine blogs you can only read through Google Reader. And if Google Reader shuts down, you can't read those blogs any more. But that'll never happen right? (which, of course, I see you've covered as I read further through your thread! π )  @cwebber if content addressed storage is considered a new idea then I'm done. I quit  @cwebber Writing a response to this while acknowledging that you're not done with the thread yet. I think the pro-bsky view is that "just" hosting a PDS counts as data independence. If this is true, then Bsky has the additional advantage (vs GTS) of shrinking outgoing bandwidth costs to something viable for hosting a few thousand users. They'd argue that hosting a relay isn't necessary because the "god's eye" view you talk about is really just the one true unopinionated view of the network. /3 @cwebber This is different from e.g. Google because Google offers an opionated view of the web. The Bsky appview is more Google Reader than Google Search (as you've pointed out). I think the "headcanon" is that anyone can make their own relay (or even did:plc maybe) because these are thought of as (caching) dumb pipes to the underlying data. There's no *reason* to run an alternate relay so long as the official one acts as a free dumb pipe, and the possibility of making one keeps them honest. /3 @cwebber But I think you're right that this starts to come apart at the seams. In fact, as you pointed out, the relay isn't neutral. It deletes spam and removes illegal content. That's important not just because of the operating costs, but because it means that the headcanon one-true-AT-network doesn't really exist; what exists is something much more centralized and hard to duplicate. I don't have a good response to this. I think if you want relay independence, Bsky isn't likely to cut it. One thing I didn't think to say in the above is that you can imagine a distributed ledger for did:plc and the relay - which doesn't currently exist. If one did exist, then there would be a practical way to keep Bluesky honest. Bsky proponents seem to think that Bluesky is meant to behave *as if* did:plc and the relay were like this, and if they start misbehaving you can fork the network. But the fact that Bsky doesn't, and *can't*, be neutral throws a wrench into this. |
Gregory's Server
ATProto is not designed for the Relay and AppViews to only hold part of the network, not *really*, and ActivityPub is. We'll get to this in a moment.
But Bluesky actually has good justification for this! I will defend it insofar as Bluesky was making a serious *design decision*