this post was submitted on 27 Jun 2023
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Lemmy

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FYI: even Lemmy servers upgraded to 0.18.0 are having problems replicating comments to each other. Missing comments on posts examples (lemmy.ml)
submitted 1 year ago by [email protected] to c/[email protected]
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Ok, so I have some code to crawl a posting of a community and compare two servers for comments missing. It looks bad today. Both of these servers are version 0.18.0 and have been upgraded for several days.

missing 0 unequal 0 11 on https://lemmy.ml/ vs. 11 on https://sh.itjust.works/
missing 35 unequal 1 48 on https://lemmy.ml/ vs. 14 on https://sh.itjust.works/
missing 4 unequal 0 9 on https://lemmy.ml/ vs. 5 on https://sh.itjust.works/
missing 6 unequal 0 9 on https://lemmy.ml/ vs. 3 on https://sh.itjust.works/
missing 1 unequal 0 1 on https://lemmy.ml/ vs. 0 on https://sh.itjust.works/
missing 6 unequal 0 12 on https://lemmy.ml/ vs. 6 on https://sh.itjust.works/
missing 3 unequal 0 8 on https://lemmy.ml/ vs. 5 on https://sh.itjust.works/
missing 3 unequal 0 6 on https://lemmy.ml/ vs. 4 on https://sh.itjust.works/
missing 22 unequal 0 42 on https://lemmy.ml/ vs. 20 on https://sh.itjust.works/
missing 5 unequal 0 15 on https://lemmy.ml/ vs. 10 on https://sh.itjust.works/
missing 8 unequal 2 17 on https://lemmy.ml/ vs. 9 on https://sh.itjust.works/
missing 3 unequal 0 3 on https://lemmy.ml/ vs. 0 on https://sh.itjust.works/
missing 0 unequal 0 10 on https://lemmy.ml/ vs. 10 on https://sh.itjust.works/
missing 11 unequal 0 24 on https://lemmy.ml/ vs. 13 on https://sh.itjust.works/
missing 1 unequal 0 2 on https://lemmy.ml/ vs. 1 on https://sh.itjust.works/
missing 13 unequal 0 37 on https://lemmy.ml/ vs. 24 on https://sh.itjust.works/
missing 3 unequal 0 7 on https://lemmy.ml/ vs. 4 on https://sh.itjust.works/
missing 0 unequal 0 10 on https://lemmy.ml/ vs. 10 on https://sh.itjust.works/
missing 60 unequal 2 186 on https://lemmy.ml/ vs. 126 on https://sh.itjust.works/
missing 10 unequal 2 51 on https://lemmy.ml/ vs. 41 on https://sh.itjust.works/
missing 16 unequal 0 51 on https://lemmy.ml/ vs. 36 on https://sh.itjust.works/
missing 31 unequal 3 128 on https://lemmy.ml/ vs. 97 on https://sh.itjust.works/
missing 0 unequal 0 4 on https://lemmy.ml/ vs. 4 on https://sh.itjust.works/
missing 2 unequal 0 5 on https://lemmy.ml/ vs. 3 on https://sh.itjust.works/
missing 15 unequal 1 67 on https://lemmy.ml/ vs. 52 on https://sh.itjust.works/
missing 4 unequal 0 53 on https://lemmy.ml/ vs. 49 on https://sh.itjust.works/
missing 0 unequal 0 5 on https://lemmy.ml/ vs. 5 on https://sh.itjust.works/
missing 0 unequal 0 0 on https://lemmy.ml/ vs. 0 on https://sh.itjust.works/
missing 1 unequal 0 19 on https://lemmy.ml/ vs. 18 on https://sh.itjust.works/
missing 0 unequal 0 2 on https://lemmy.ml/ vs. 2 on https://sh.itjust.works/
missing 0 unequal 0 22 on https://lemmy.ml/ vs. 22 on https://sh.itjust.works/
missing 0 unequal 0 16 on https://lemmy.ml/ vs. 18 on https://sh.itjust.works/
missing 0 unequal 0 7 on https://lemmy.ml/ vs. 7 on https://sh.itjust.works/
missing 3 unequal 0 27 on https://lemmy.ml/ vs. 24 on https://sh.itjust.works/
missing 2 unequal 0 32 on https://lemmy.ml/ vs. 30 on https://sh.itjust.works/
missing 3 unequal 0 21 on https://lemmy.ml/ vs. 18 on https://sh.itjust.works/
missing 3 unequal 1 16 on https://lemmy.ml/ vs. 13 on https://sh.itjust.works/
missing 3 unequal 1 47 on https://lemmy.ml/ vs. 44 on https://sh.itjust.works/
missing 1 unequal 0 24 on https://lemmy.ml/ vs. 23 on https://sh.itjust.works/

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[–] [email protected] 1 points 1 year ago (2 children)

How much of this is just the nature of activity pub and federation over it?

Putting aside whether lemmy is doing a good or bad job, it seems like an issue at the protocol level? For instance, if lemmy were to implement some additional procedures as you hint at, would they work for federation outside of lemmy or would they even cause problems or bugs?

I’m pretty sure I’ve seen things get dropped in similar ways on other micro-blog platforms. It could be that the community/group based structure just surfaces the issues more because you can compare whole communities instead of individual reply threads in microblogging. Maybe activity pub isn’t appropriate for federated group activity?

Have you looked at similar issues with kbin?

Also, thanks for this work. High level end-to-end testing like this is probably invaluable!!

[–] [email protected] 3 points 1 year ago

I haven't had time to look at kbin.

The Lemmy servers are logging errors, but the messages need organization and are rather difficult to access by server operators. Growing pains.

[–] [email protected] 1 points 1 year ago (1 children)

Just to pose these in a similar thread, I have a few questions as a casual observer, some of which I'm unclear if they're handled at the protocol or Lemmy level.

  • As I understand it servers subscribe to other servers and everything is then push based?
  • I assume ordering is not a guarantee. So there's probably no concept of offset tracking on subscriptions or replaying a time range?
  • If ordering is not a requirement how do likes/comments handle out of order receipt? Everything seems to have a local ID, so can content get pre-liked before the root message arrives? Unclear if ID generation is based on any identifiers you'd have to work with or not - or whether remote content retains its origin IDs?
  • Lemmy at least appears to have some retry mechanism, but I'm unclear the behavior on that - seems annoying with 1000+ subscribing servers.
  • I seem to recall reading ActivityPub has some pattern for batching, but reading the spec again I'm not seeing it. Is that a thing?
[–] [email protected] 1 points 1 year ago

Sorry I don’t know the answers to these questions. Also, I don’t think the OP will get a notification for your content (?) unless you reply to them directly, just in case you want to ask them.