Why does /All show different posts in different instances? - eviltoast

Like many others, I created accounts on a few different instances to try things out. Using apps like Liftoff and Jerboa make it very convenient to switch between accounts, but I’ve noticed that I get different posts showing up when browsing All, even with the same sort settings.

Can someone explain why that would be? I don’t think any of the instances I’m on are defederated, so shouldn’t I see the same posts across different instances?

  • SolidGrue@lemmy.world
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    1 year ago

    Imagine 5 instances, all federated with each other. That means each instance maintains one connection to each of the other 4 instances, and there are 25 connections in total.

    One of those instances is bigger than all of the other four combined, and it’s struggling to keep up. In one 5-minute window, there are 300 messages to send to each of the other servers, or 1200 messages. These messages are all of new posts, new subscriptions, new commenta, new up/down votes, new edits, new deletes, and new mod actions. The server only has resources to send maybe 800 or 1000 messages to the other four instances, so the last 200 get queued.

    And then the next 5-minute window opens with 1200 MORE messages. Except we still have the 200 messages from that last window to clear. Evertthng else being equal, at the end of THIS window we might have 400 messages queued. So on and so forth, more messages get queued and the goal posts recede faster than the speed of light. Eventually the server runs of of queue, and messages (at best) get dropped. Ultimately tjenserver crashes and restarts and those messages in the queue get lost. (There’s an announcement on the main page)

    Lemmy.world.is that big server, and its subscriber instances are getting inconsistent updates because Lemmy.world’s server is resource starved from the massive influx of new users and traffic this weekend.

    Have patience. It’ll smooth out, but it will take time.