this post was submitted on 20 Oct 2026
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I shared a link from NPR Tiny Desk but there was no image preview or video embed. After investigating this I learned that when you do that, each instance picks up the link and individually retrieves the link preview nearly simultaneously. For gargantuan sites like YT or Reddit, this is a trivial amount of traffic and not a problem, but for smaller sites like NPR this results in a sort of botnet DDOS attack on the site's servers. More here. Another example here . For that reason, NPR has blocked Fediverse servers like Mastodon.

I have experienced this on my personal server as well (DDOS), but at the time didn't know why, exactly.

This isn't the end of the world, but certainly is not great and hurts engagement with the content. Is there a solution for this? Perhaps using some sort of webtorrent service like PeerTube where they just fetch the information from another fediverse server instead of the source server? Maybe fetching embeds client-side? At least that would stagger the requests.

E: Many people have replied comparing this to the Reddit "hug of death" or "The Slashdot effect". This is not the same at all. Those are legitimate site visits from humans that happen over the course of several hours. This is the result of several thousand servers all automatically fetching the same image simultaneously , and without any human involvement, and potentially next to zero human traffic to the site, which is why I compared it to a botnet or DDOS attack.

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[–] yuki2501@lemmy.world 1 points 1 hour ago (1 children)

Heh. Ever heard of the Slashdot effect?

[–] artyom@piefed.social 5 points 1 hour ago

For the fifth fucking time, this is not the same thing .

[–] trebach@sh.itjust.works 2 points 4 hours ago

I added a rule in my .htaccess for their user agents to direct all requests to a static page on my domain.

[–] ipkpjersi@lemmy.ml 1 points 4 hours ago (1 children)

Same thing used to happen with reddit giving sites the hug of death lol

It's unfortunate but kind of expected.

[–] artyom@piefed.social 8 points 3 hours ago

Its not at all the same thing

[–] Blackmist@feddit.uk 15 points 15 hours ago (1 children)

Sounds like every instance is doing the preview generation. Maybe it could grab the preview data it needs on the original instance, and pass that around with the post...

[–] boonhet@sopuli.xyz 1 points 12 minutes ago

Well you can't really trust the original instance to be truthful with its preview.

[–] asudox@lemmy.asudox.dev 4 points 12 hours ago* (last edited 12 hours ago) (1 children)

Why not have the users fetch the previews themselves. The user's browser, that is.

[–] wasu@lemmy.world 5 points 8 hours ago

For sure there is more users than instances. So the amount of requests would be grater but at least they wouldn't happen at the same time.

But if fediverse ever grow to be as big as other social media, then a single post/link can be viewed by thousands of users at the same time causing the same effect.

[–] AdrianTheFrog@lemmy.world 13 points 23 hours ago (1 children)

it seems like ideally it shouldn't attempt to preview the link before a user tries to view the content. i guess that would increase latency for users though

[–] artyom@piefed.social 6 points 23 hours ago

Sure would.

[–] A_Random_Idiot@lemmy.world 26 points 1 day ago (1 children)

So we need people to just mass post links to bad websites, is what you're saying.

i'm feeling less ambivalent about those reddit repost bots for a moment

[–] CultLeader4Hire@lemmy.world 37 points 1 day ago (2 children)

Is this the same thing as the “Reddit hug of death”?

[–] FluorineBalloon@programming.dev 68 points 1 day ago (1 children)

Similar, except those are caused by users visiting a link, whereas the Fediverse issue is federated servers gathering info before users even see a link.

[–] trolololol@lemmy.world 5 points 1 day ago

How many servers are we talking about? 10,000 ?

[–] 0x0@lemmy.zip 17 points 1 day ago (1 children)
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[–] FundMECFS@piefed.zip 82 points 1 day ago (1 children)

Thanks for bringing this up. I think in general we need to work on optimisation of Activitypub and Threadiverse implementations of it.

[–] derpgon@programming.dev 10 points 1 day ago

Either publishing server should serve the metadata - although it would be prone to bad actors, so a refetch in the next 0-180 seconds would be appropriate. Or just add a random 0-60 second delay before fetching the data.

[–] GenosseFlosse@feddit.org 54 points 1 day ago (1 children)

Is there a reason why the publishing instance is not downloading the preview image, and then submits it with the post to the other instances? This way they would not have to fetch it themselves.

[–] Funkt4st1c@lemmy.world 39 points 1 day ago (8 children)

Yeah, thats how it should be: one download, everyone else downloads from that server, not the original source.

Seems abusable though

[–] _haha_oh_wow_@sh.itjust.works 21 points 1 day ago

It is, but that's what defederation is for: If there are instances that are being sketchy, they are supposed to get cut off from the rest of the Fediverse.

[–] Gibibit@lemmy.world 25 points 1 day ago

Seems abusable though

If one instance doesn't trust another, they shouldn't federate in the first place.

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[–] cybervegan@lemmy.world 43 points 1 day ago (4 children)

I have my blog address (which goes to my home server) in my Mastodon profile, and every time I post on Masto, my server gets a request from every Mastodon site that federates with my instance - i.e. hundreds of requests. It's no problem for my server, because my blog is a static site, but for anything that dynamically generates every single page impression (like worpress or joomla), it could be a problem. Caching settings might help, I suppose.

Truth is, though, I get far more traffic from vulnerability scanners and AI crawlers that don't honour robots.txt (or aren't yet listed).

[–] iglou@programming.dev 2 points 17 hours ago (1 children)

To be honest, if a website has no caching of their server-rendered parts, they are also doing something wrong! Very little sites really need to re-render a public page on every view.

[–] cybervegan@lemmy.world 6 points 17 hours ago

Around 2010, I used to work at an MSP, and once had a customer that ran a custom LAMP stack website for local radio UK stations web presence. It was a bit slow, running on a dedicated physical server, but every time it snowed, the website would 500 out - because of too many requests to the "School Closures" page. The site had no caching other than Apache's internal cache, but PHP pages could not be cached because "reasons", and the original developer was "not available". I optimised their MySQL indexes, increased the number of Apache workers, and it improved the render time per page and number of concurrent connections. Stress testing looked good.

Anyway, some months later, 2AM one snowy morning, I was on call, and it went down again. This was when I discovered the school closures problem. After diagnosing, and then liaising with the customer to discuss the options, I was told "just make it work". I ended up modifying the PHP script to add some "on spec" caching that saved the HTML to a temp file in ramdisk, and only re-ran the query-and-render code if the cached copy was more than 5 minutes old. It was hacky, but it did the trick, and I was finished by about 4 AM. This hack was later applied at their request to a number of trouble-points in the source tree, as and when things broke.

We recommended adding a Varnish cache, and found a more generalised caching library but they wouldn't/couldn't authorise engineering work for this - they were running on a shoestring - and they already had the tech break-fix contract with us, and decided it was sufficient to just spot fix things as they broke rather than fix the root cause.

I left that MSP in 2012, so I don't know what happened after that, but as far as I know, the site could still be running.... unlikely, but possible.

[–] 0x0@lemmy.zip 12 points 1 day ago (1 children)

that don’t honour robots.txt (or aren’t yet listed).

Throw'em in the tar pit.

[–] cybervegan@lemmy.world 3 points 16 hours ago

Limited mental capacity these days, so I don't have the spoons to properly research and implement a solution at the moment. I installed Nepenthes last year, but I've never managed to get round to integrating it into my site. It's low priority at the moment.

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[–] wjs018@piefed.wjs018.xyz 218 points 2 days ago (17 children)

There are two proposed solutions I have seen. I do not claim that this is exhaustive, just only limited to the proposals that I have stumbled across.

FASP - Fediverse Auxiliary Service Provider

The idea that mastodon has is to have a third-party service that does something like generate a link preview once and then share that to fediverse instances that need it. They have a whole spec they wrote up about these kinds of services that can be run to help out fediverse instances with different things like this, search, or discoverability. They call these FASPs - the repo with the spec is here.

I don't yet know of any FASP that is live and running, so it is kind of a paper spec at the moment. I don't do too much on the microblogging side of the fediverse though, so I very well could be wrong.

Federate link metadata and the post at the same time

This comes from an issue on PieFed's repo. It is basically just an idea at this point, but it is a pretty basic one; have the originating instance fetch the link preview information and simply federate it out alongside the post itself.

[–] jaybone@lemmy.zip 130 points 2 days ago (12 children)

That second solution is what I thought of as doing as I read this. It doesn’t rely on a third party service being up. And that instance has to do that work anyway. So why not just share the results with others?

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[–] dropdrip@lemmy.ml 35 points 1 day ago (7 children)

It's almost like the software that powers the internet was designed for a different time and is only still used because there's monied interest in keeping it around. We need GNUnet.

[–] milbyte11@lemmy.ml 23 points 1 day ago

is there something that makes this different to 17 other proposals for a new internet or is it just a case of https://xkcd.com/927/

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[–] ByteJunk@lemmy.world 45 points 1 day ago (14 children)

I mean, just how many instances are gonna ping the URL? Several hundred, low thousands at worst?

Unless it happens to be some very large media content or a dynamic page with no caching, I'd think the automated federation hits shouldn't be too bad.

The influx of users that might come after a viral post though, that's rough....

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[–] KeenFlame@feddit.nu -3 points 15 hours ago (1 children)

I'm not exactly sure why a web server can't handle legit web traffic, just because it's a lot? I agree that smaller actors should be given a little breastfeeding but solving it on the other side is bad architecture. A legit request can never be compared to a a ddos attack, the overloaded net has to throttle and then the instances need to retry with a generous enough delay.

Options for solutions to another systems problems are all going to introduce more problems. Sure, the requests could honestly be routed to a cache and it would help this problem, att least until it breaks or is exploited. But it would never be truly solved that way.

[–] artyom@piefed.social 6 points 15 hours ago (1 children)

I'm not exactly sure why a web server can't handle legit web traffic, just because it's a lot?

Its not because it's a lot, it's because it all happens in the same instant, which does not resemble any sort of normal web traffic.

but solving it on the other side is bad architecture

Solving it on the side that's creating the problem is bad architecture? 🤔

But it would never be truly solved that way.

Several potential solutions have been posited, if you just look through the comments.

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