Implement support for `--compression` in `lxc export`

[ghost]

Required information

• Distribution: ubuntu
• Distribution version: 19.10
• The output of
  • lxc-start --version 3.0.3

Issue description

Please add --compression off switch to the lxc export command

I export large images from my laptop to another computer on my local network. gzip puts a lot of load on the laptop CPU. I would prefer to have an option to switch off the compression since moving large images in a local network is not a problem.

[stgraber]

This should be implemented the same way things are done for lxc publish.

Note that a current workaround is to set backups.compression_algorithm as a global setting, if you set it to none then it won't compress.

[ghost]

thanks @stgraber I'll try to use workaround until the solution is implemented

[ghost]

hey @stgraber would something like this work? https://github.com/lxc/lxd/compare/master...srados:no-compression-backup

it's not finished but I wanted to see if this is the way to go.

[ghost]

oh, or shall I copy the lxc publish approach to maintain uniformity?

[stgraber]

I'd prefer it work the same way we've done for lxc publish.

[stgraber]

Assigning to you since you seem to have most of the pieces figured out already :)

[stgraber]

As far as how we usually split commits for this type of work, it'd look like:

• api: Add backup_compression_algorithm API extension
  • Adds that string to shared/version/api.go
  • Adds a description in doc/api-extensions.md
• shared/api: Add CompressionAlgorithm to InstanceBackupsPost
  • Add the new field to InstanceBackupsPost in shared/api/instance_backup.go
  • The field should be added at the end of the struct, after a API extension: backup_compression_algorithm comment which is itself preceded by a line break (see image.go for examples).
• lxd/backups: Add support for CompressionAlgorithm
  • The actual change to the creation logic
• lxc/export: Add --compression option
  • The change to the client to set the option based on the command line argument
• i18n: Update translation templates
  • As the previous commit changes translated strings, you need a commit that updates the translation templates. You can generate the content of this commit by running make i18n.

Let me know if you need any help with this!

[stgraber]

Thanks!

[ghost]

I may ping you in order to find out how you test the changes, otherwise I think I'll be fine ;)

[ghost]

@stgraber shall I log backup_compression_algorithm to instances_backups table? If yes, where do I create migration to add new field to that table?

[stgraber]

No, we don't need to record the compression algorithm, we have logic to figure it out from the on-disk files.

[ghost]

is there an easy way to test my changes? I ran make and I have binaries, but I'm not sure how to set the whole system up

[stgraber]

If you're using the snap, you can move your locally built binaries to:

• /var/snap/lxd/common/lxd.debug
• /var/snap/lxd/common/lxc.debug

Then reload LXD with systemctl reload snap.lxd.daemon which will then have it start from the debug binaries.

[ghost]

Thanks for the tip...this would definitely help me stop programming in the dark :)

[stgraber]

Seems to be working well from a quick local test.

[ghost]

Great. Thanks for all the help and such an awesome project!

[stgraber]

Np, thanks for the contribution!