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How Discord Resizes 150M Images Every Day with Go and C++

blog.discordapp.com

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Re: How Discord Resizes 150M Images Every Day with Go and C++

#21

Post by timdorr »

Xeoncross wrote: post #8

Why don't more companies resize images client-side first using and then save the server some work by only asking it to verify the result by - resizing to the same size - removing metadata This results in much faster transfer (10x less bandwidth used often for mobile uploads) and reduces server load by "farming" out the work to the clients. https://developer.mozilla.org/en-US/docs/Web/API/CanvasRende... # Edit: On Kee…

These images are often links from the web or posted by a bot, so they're not on a client until after they've been served.

Re: How Discord Resizes 150M Images Every Day with Go and C++

#22

Post by sgk284 »

There is already an (unofficial Google) image proxy written in Go that is quite fast, does caching (local or backed by S3/GCS), and does other nice things like smart cropping: https://github.com/willnorris/imageproxy

Seemed like a lot of unnecessary work for them to reimplement a service from scratch without gaining any major perf benefits over their existing one and without leaning on an existing well-known and well-built foundation.

Re: How Discord Resizes 150M Images Every Day with Go and C++

#23

Post by pmelendez »

Xeoncross wrote: post #8

Why don't more companies resize images client-side first using and then save the server some work by only asking it to verify the result by - resizing to the same size - removing metadata This results in much faster transfer (10x less bandwidth used often for mobile uploads) and reduces server load by "farming" out the work to the clients. https://developer.mozilla.org/en-US/docs/Web/API/CanvasRende... # Edit: On Kee…

From the notes of your link:

"drawImage() will ignore all EXIF metadata in images, including the Orientation. This behavior is espacially troublesome on iOS devices. You should detect the Orientation yourself and use rotate() to make it right. "

If the origin of the image is the client and you got the client side resize wrong, then you might introduce artifacts when trying to fix it on the server because the data loss. Also if clients are mobile, you might like to optimize the battery of clients instead of computing time on the server.

Re: How Discord Resizes 150M Images Every Day with Go and C++

#24

Post by Xeoncross »

b1naryth1ef wrote: post #20
Xeoncross wrote: post #8

Why don't more companies resize images client-side first using and then save the server some work by only asking it to verify the result by - resizing to the same size - removing metadata This results in much faster transfer (10x less bandwidth used often for mobile uploads) and reduces server load by "farming" out the work to the clients. https://developer.mozilla.org/en-US/docs/Web/API/CanvasRende... # Edit: On Kee…

As mentioned in the post, one of our core product features is preventing your IP from being shared. Given that requirement, images shared in chat have to be proxied through our infrastructure. When doing this we save a lot of money and improve client performance by reducing image sizes.

So why the image can't first be resized/compressed before being sent through your infrastructure...?

Re: How Discord Resizes 150M Images Every Day with Go and C++

#25

Post by detaro »

throwthisawayt wrote: post #2

Did it seem to anyone else that sticking to Python would have been way easier? It didn’t seem like any of the performance gains were through Golang.

I don't think the article gives us the data to know this. Where did the latency spikes in the original implementation come from? Would fixing them have required a complete rewrite of the Python parts anyways?

Re: How Discord Resizes 150M Images Every Day with Go and C++

#26

Post by sgk284 »

Xeoncross wrote: post #8

Why don't more companies resize images client-side first using and then save the server some work by only asking it to verify the result by - resizing to the same size - removing metadata This results in much faster transfer (10x less bandwidth used often for mobile uploads) and reduces server load by "farming" out the work to the clients. https://developer.mozilla.org/en-US/docs/Web/API/CanvasRende... # Edit: On Kee…

You often want the original because different clients may display different sizes.

Re: How Discord Resizes 150M Images Every Day with Go and C++

#27

Post by devwastaken »

How is the security? Any sort of image processing is a potential exploitation point. I see it says it uses the 'mature' libjpeg-turbo and libpng libraries,along with giflib for .gifs, but even with full trust of those, the C code, patches, and changes ontop could be more exploitation points. You can look through Imagemagick alone to see all the fun things possible when seemingly basic processing turns into exploits. https://www.cvedetails.com/vulnerability-list/vendor_id-1749...

Re: How Discord Resizes 150M Images Every Day with Go and C++

#28

Post by Xeoncross »

pmelendez wrote: post #23
Xeoncross wrote: post #8

Why don't more companies resize images client-side first using and then save the server some work by only asking it to verify the result by - resizing to the same size - removing metadata This results in much faster transfer (10x less bandwidth used often for mobile uploads) and reduces server load by "farming" out the work to the clients. https://developer.mozilla.org/en-US/docs/Web/API/CanvasRende... # Edit: On Kee…

From the notes of your link: "drawImage() will ignore all EXIF metadata in images, including the Orientation. This behavior is espacially troublesome on iOS devices. You should detect the Orientation yourself and use rotate() to make it right. " If the origin of the image is the client and you got the client side resize wrong, then you might introduce artifacts when trying to fix it on the server because the data los…

Even several years ago there were libraries on github that accounted for iOS defects. However, that aside, just skip the resize on iOS and send as-is. The server still has to verify the result anyway.

Re: How Discord Resizes 150M Images Every Day with Go and C++

#29

Post by b1naryth1ef »

Xeoncross wrote: post #24
b1naryth1ef wrote: post #20

Earlier quoted context omitted.

As mentioned in the post, one of our core product features is preventing your IP from being shared. Given that requirement, images shared in chat have to be proxied through our infrastructure. When doing this we save a lot of money and improve client performance by reducing image sizes.

So why the image can't first be resized/compressed before being sent through your infrastructure...?

Ah sorry I misunderstood you. We keep the original image around and provide different sizes for different platforms/resolutions/dpis/etc.

Re: How Discord Resizes 150M Images Every Day with Go and C++

#30

Post by Buttons840 »

devwastaken wrote: post #27

How is the security? Any sort of image processing is a potential exploitation point. I see it says it uses the 'mature' libjpeg-turbo and libpng libraries,along with giflib for .gifs, but even with full trust of those, the C code, patches, and changes ontop could be more exploitation points. You can look through Imagemagick alone to see all the fun things possible when seemingly basic processing turns into exploits.…

Wow really? Is there room for another image processing library? Is ImageMagic poorly written or is image manipulation inherently risky?
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