Wanting to add high value content to this community consistently to keep it alive and interesting for new subscribers. Am excited for the future of this Lemmy community
this post was submitted on 03 Jul 2023
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Thanks for sharing @[email protected]
@[email protected] I'm pretty sure it's hosted on slrpnk.net even though it was posted by a user on lemmy.world . Just decentralization and interoperability working as they should.
Are you sure? When I hover over the words "lemmy.world" it shows the full URL destination for the link, and I can see that when I click on the image it's hosted at "https://lemmy.world/pictrs/image/3a12d532-f0f4-4f90-9a66-406e746f5183.jpeg".
It really looks like it's hosted on lemmy.world.
Does anyone have any information (ideally at a very accessible level, possibly with a diagram) that explains where files are hosted and how they're posted across non-local servers?
Yes, images from other Lemmy instances are currently not cached. Image caching in Lemmy a bit of a complex mess that makes it hard to understand when a image is cached on the local instance or not.
Edit: basically what happens is: If you upload an image directly this local link will be shared to other instances and they will show it like in this post. The image upload host is always your home instance, so even when posting to a remote community your home instance will host the image.
But it you link to an external image host like imgur, then the home instance will pull a local copy in its cache and show that. However it federates the original link to imgur and not the local cached link, thus on other instances the picture will be loaded from imgur.
I think the latter part is an unintended side-effect of an incomplete caching implementation in Pict-rs / Lemmy.
Thanks for the explanation.
Do you have any advice on how to post images? I'd like to be mindful of hosting costs. Is sharing a link to Google photos better than downloading and uploading, for instance?
For now uploading them here is no problem. If you want you can scale down the image a bit, but I'll probably do that automatically on the server soon.
The entire image hosting situation is not very satisfactory on Lemmy in general right now, so I expect there to be some bigger changes in the backend anyway. Thus not much point optimizing it right now.
Thanks, that's good to know.
Separately, though, it's certainly easier to copy and paste URLs than download and upload. Does linking to images on the web work, if I find it more convenient?
Sure, you do you. Just depending on the link people from other instances might not be able to access it.
Okay, though I don't want to post in a way that makes it inaccessible to anyone. When you say that depending on the link, people from other instances might not be able to access it, what does that depend on?
If for the moment I'm only talking about files hosted on reddit, do you know if I copy and paste the URL for the content itself whether people on other instances will see the image naively as though I'd downloaded it and uploaded it?
For external links it is impossible to say what rate limits and other deeplinking protections are deployed. Obviously Reddit does not want people to use their servers for hosting images on external websites. So it might look fine to you, but other people that try to access the image URL the fist time are blocked.
Right now Lemmy seems to cache external images only for local users, if you access through a remote instance you will get the original external link.
Alright. It seems like I should upload images of I want to ensure their visibility. I'll keep testing things and learning. Thanks for the explanation.
Thanks for your information. As I said I was "pretty sure" which isn't to say "sure" or positive and possibly incorrect. I do see see what you're referring to. My understanding on how activitypub works to federate is that it's sent FROM lemmy.world and the originating user TO slpnk.net as it lists in the heading just like sending email from one server to another. The Lemmy Devs mention this at https://join-lemmy.org/docs/introduction.html "Just like a traditional website, people sign up on it, post messages, upload pictures and talk to each other. Unlike a traditional website, Lemmy instances can interoperate, letting their users communicate with each other; just like you can send an email from your Gmail account to someone from Outlook, Fastmail, Proton Mail, or any other email provider, as long as you know their email address, you can mention or message anyone on any website using their address."
From my understanding, Activitypub uses lots of copies just like there is a copy of this post on any Mastodon or other Fediverse servers that are federated with us so there may be more than one server hosting the image. If you click through on the link above you may find some useful explainers and you might get a more technical response from another Fediverse focused community like [email protected] or [email protected]