Hi. Just looking at what lemmy.ca sends my server:
From nginx log:
your.ip.address - - [20/Feb/2024:03:48:47 +0000] "POST /inbox HTTP/1.1" 200 0 "-" "Lemmy/0.19.3; +https://lemmy.ca"
your.ip.address - - [20/Feb/2024:03:48:49 +0000] "POST /inbox HTTP/1.1" 400 0 "-" "Lemmy/0.19.3; +https://lemmy.ca"
your.ip.address - - [20/Feb/2024:03:48:57 +0000] "POST /inbox HTTP/1.1" 400 0 "-" "Lemmy/0.19.3; +https://lemmy.ca"
Dumping the JSONs reveals 3 duplicate files, all containing:
"id": "https://lemmy.ca/activities/create/0968bf93-ac05-4178-bf3f-28cdc65fc338"
"actor": "https://lemmy.ca/u/HairyOldCoot"
"object": {
"id": "https://lemmy.ca/comment/7454502"
"content": "That was an episode of Sliders."
"published": "2024-02-20T03:48:45.810068Z"
These are 3 Creates, not 1 Create and 2 Updates or anything. I've chosen a comment 'cos that's public info, but it's the same for all other activity too (Votes, Deletes, etc).
lemmy.ca isn't alone in this. endlesstalk.org sends everything twice (info posted here), as does lemmy.sdf.org and mander.xyz, but lemmy.ca is the only one I've seen send stuff 3 times. Other instances (e.g. aussie.zone, feddit.nl, lemm.ee, lemmings.world, lemmy.world, programming.dev, reddthat.com, sh.itjust.works, slrpnk.net) don't, but there's nothing obvious like lemmy version numbers to indicate the difference.
Whilst I'd prefer you didn't send me stuff 3 times, I'm mostly mentioning it because I doubt it's good for your own resources to send every activity by every lemmy.ca user out multiple times. Also, the OPs of my community are from Mastodon, so I imagine you're sending them the same message 3 times too ...