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Cake day: March 24th, 2024

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  • It should be noted that the (visibility of) community bans are a result of better enforcement of site bans in 0.19.4, which for now is implemented by sending out community bans for local communities when a user gets instance banned: https://github.com/LemmyNet/lemmy/pull/4464

    Prior to this, when a user got instance banned from .ml, they were also implicitly banned from .ml communities, but this was only known to the instance they were banned on. As a result, users were still able to post, comment, and vote on those communities, but it would be visible only on that user’s instance, not federated anywhere else. Visibility of this ban was exclusively on the banning instance’s modlog.

    fyi @SpaceCadet@feddit.nl






  • lemmy’s current federation implementation works with a sending queue, so it stores a list of activities to be sent in its database. there is a worker running for each linked instance checking if an activity should be sent to that instance, and if it should, then send it. due to how this is currently implemented, this is always only sending a single activity at a time, waiting for this activity to be successfully sent (or rejected), then sending the next one.

    an activity is any federation message when an instance informs another instance about something happening. this includes posts, comments, votes, reports, private messages, moderation actions, and a few others.

    let’s assume an activity is generated on lemmy.world every second. now every second this worker will send this activity from helsinki to sydney and wait for the response, then wait for the next activity to be available. to simplify things, i’ll skip processing time in this example and just work with raw latency, based on the number you provided. now lemmy.world has to send an activity to sydney. this takes approximately 160ms. aussie.zone immediately responds, which takes 160ms for the response to get back to helsinki. in sum this means the entire process took 320ms. as long as only one activity is generated per second, this is easy to keep up with. still assuming there is no other time needed for any processing, this means about 3.125 activities can be transmitted from lemmy.world to aussie.zone on average.

    the real activity generation rate on lemmy.world is quite a bit higher than 3.125 activities per second, and in reality there are also other things that take up some time during this process. over the last 7 days, lemmy.world had an average activity generation rate of about 5.45 activities per second. it is important to note here that not all activities generated on an instance will be sent to all other linked instance, so this isn’t a reliable number of how many activities are actually supposed to be sent to aussie.zone every second, rather an upper limit. for example, for content in a community, lemmy will only send these activities to other instances that have at least one subscriber on the remote instance. although only a fraction of the activities, private messages are another example of an activity that is only sent to a single linked instance.

    to answer the original question: the week of delay is simply built up over time, as the amount of lag just keeps growing.

    additionally, lemmy also discards its queued activities that are older than a week once a week, so if you go over 7 days of lag for too long you will start completely missing activities that were over the limit. as previously explained, this can be any kind of federated content. it can be posts, comments, votes, which are usually not that important, but it can also affect private messages, which are then just lost without the sender ever knowing.


  • it’s open source: https://github.com/Nothing4You/activitypub-federation-queue-batcher

    I strongly recommend fully understanding how it works, which failure scenarios there are and how to recover from them before deploying it in production though. not all of this is currently documented, a lot of it has just been in matrix discussions.

    I also have a script to prefetch posts and comments from remote communities before they’d get through via federation, which would make them appear without votes at least, and slightly improve processing speed while they’re coming in through regular federation. this also doesn’t require any additional privileges or being in a position to intercept traffic. it is however also not enough to catch up and stay caught up.
    this script is not open source currently. while it’s fairly simple and straightforward, i just didn’t bother cleaning it up for publishing, as it’s currently still partially integrated in an unrelated tool.
    I previously tried offering to deploy this on matrix but one of my attempts to open a conversation was rejected and the other one never got accepted.




  • stating that it’s an issue on our end as our server isn’t keeping up

    this isn’t exactly an issue in your end, unless you consider hosting the server in Australia as your issue. the problem is the latency across the world and lemmy not sending multiple activities simultaneously. there is nothing LW can do about this. as unfortunate as it is, the “best” solution at the time would be moving the server to Europe.

    there are still some options besides moving the server entirely though. if you can get the activities to lemmy without as many delays am experience similar to being hosted in Europe can be achieved.


  • aussie.zone is just not keeping up with the amount of activities generated on lemmy.world.

    it’s not going lower than a week anymore without actively doing something to improve this situation, and once a week all activities older than a week that haven’t been received from LW yet will be discarded on LWs end.

    this is most likely mostly caused by latency from LW (finland) to aussie.zone, as lemmy only sends one activity at a time, requiring a round trip across the world for every single activity activity before sending the next one.

    there are a couple things that can cause comments to show up on aussie.zone before they would regularly federate, such as someone searching the post/comment url on aussie.zone. some clients will do this automatically if you click a link to a post/comment from another instance.


  • lemmy currently only sends one activity per receiving instance at a time, so there is a round trip for every single post, comment, vote, etc., before the next activity will be sent. you wouldn’t see any increased number of connections, as there’s only a single one.

    do you have access logs for /inbox with the lemmy.world’s user agent? you might be able to derive some information from that if requests increased over time or something, maybe also response status codes?


  • I can’t tell you why you’re lagging but you’re clearly lagging quite a bit behind.

    which country is your instance located in?
    did you (or someone else on your instance) recently subscribe to a bunch of high traffic communities on lemmy.world, which would make lemmy.world send more activities to you?

    lemmy by default only sends activities in a community to another instance if there’s at least one subscriber to the community on that instance. if you’re located far from finland, where lemmy.world is located, you might have been able to keep up just enough before this, although this isn’t the first time as the graphs above show.



  • records can’t be duplicated in the database, the activity id is a unique key:

    lemmy=# \d sent_activity
                                                   Table "public.sent_activity"
               Column            |           Type           | Collation | Nullable |                  Default
    -----------------------------+--------------------------+-----------+----------+-------------------------------------------
     id                          | bigint                   |           | not null | nextval('sent_activity_id_seq'::regclass)
     ap_id                       | text                     |           | not null |
     data                        | json                     |           | not null |
     sensitive                   | boolean                  |           | not null |
     published                   | timestamp with time zone |           | not null | now()
     send_inboxes                | text[]                   |           | not null |
     send_community_followers_of | integer                  |           |          |
     send_all_instances          | boolean                  |           | not null |
     actor_type                  | actor_type_enum          |           | not null |
     actor_apub_id               | text                     |           |          |
    Indexes:
        "sent_activity_pkey" PRIMARY KEY, btree (id)
        "sent_activity_ap_id_key" UNIQUE CONSTRAINT, btree (ap_id)