Re: .zsync files for the weekly live images

[Roland Clobus]

On 08/04/2023 10:48, Roland Clobus wrote:

Hello Debian-Images team,

I've tested the .zsync files on [1].


As a fix, I see several possibilities, which do you prefer?

1) Turn off zsync
2) Keep zsync, and generate unique filenames





With kind regards,
Roland Clobus

[1] https://get.debian.org/images/weekly-live-builds/amd64/iso-hybrid/

They currently don't work, because the original filename (live-image-amd64.hybrid.iso) is embedded in those files. Option 1 would possibly increase the amount of traffic on get.debian.org. Are metrics available whether the .zsync files are used at all? I haven't tested whether the zsync method will work properly for the live images, as they contain a huge squashfs file embedded in the iso file (so a compressed file inside another compressed file), so I don't know whether it will help in saving bandwidth. Option 2 would mean that (with the current code) filenames can be generated with the structure `{something-we-decide}-{architecture}.hybrid.iso`, e.g. `debian-live-testing-gnome-amd64.hybrid.iso`. This is different from the current names on [1]. If we go for option 2, it will need (small) changes in the `live-build`, `live-setup` and `jenkins.debian.net` git repos.

```
verifying download...checksum matches OK
used 3612643328 local, fetched 84375881
```





This looks promising enough to prepare for option 2.

With kind regards,
Roland Clobus

In my previous mail I've expressed my doubts that zsync would be able do reduce the amount of bytes that is to be downloaded. I was able to do an experiment now, and it looks good. With the GNOME images from 2023-04-03 and 2023-04-10 I got the following output: In order to do so, I had to convince zsync to use different filename (which I managed by splitting the zsync file into its text and binary part, adjusting the text part and combining both parts again). Of the 3.6GB only 84MB needed to be downloaded, which is quite impressive, given that the compressed file `filesystem.squashfs` also has many differences. PS: I'm not the only one reporting the issue with zsync: https://lists.debian.org/debian-cd/2023/04/msg00016.html

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