buildah bud --cache-from functionality needed

[TomSweeneyRedHat]

Description
buildah bud --cache-from is missing and needs to be provided. This is functionality that Docker has.

599 is the parent issue for this issue.

Output of buildah version:

Buildah v0.16

[rhatdan]

We don't currently support cache, so this one might take a while.

[rhatdan]

Now that we have support for --cache, @umohnani8 Could you add this functionality.

[rhatdan]

@umohnani8 Any progress on this? We should get this functionality going now.

[rhatdan]

@TomSweeneyRedHat @umohnani8 Is this fixed in buildah?

[TomSweeneyRedHat]

It's still a no-op in the code with nothing really happening underneath it other than saying "not supported".

[rhatdan]

is it something we could implement?

[TomSweeneyRedHat]

I think we could get --cache-from to work for "real", but I've not dived through the code to see if we can for sure.

[rhatdan]

@rhatdan Any movement on this one?

[rhatdan]

@ashley-cui Could you take a look at this?

[mfolnovic]

Parent issue ( #599 ) was closed, so I was wondering if this will be implemented?

This has a huge impact on building images from CI.

Unfortunately this issue is the only reason I prefer Docker in CI (while living with issues Docker has). After implementing this issue, I don't see any reason to not use Buildah in CI.

Otherwise, Buildah is really awesome, nice work!

[rhatdan]

Sadly no one has picked up the work on this one yet.
@nalind WDYT?
@TomSweeneyRedHat Do you have time to look into this?
@mfolnovic Any chance you would want to take a stab?

[mfolnovic]

@rhatdan with a few pointers, I could try :) :)

[TeNNoX]

What exactly do you mean by pointers?
Implementation hints? or functionality-wise?

[mfolnovic]

@TeNNoX implementation hints :)

[haampie]

Any news on this issue?

[TomSweeneyRedHat]

@haampie I'm afraid I've not had time to look into this, I've been chasing other fires and I don't believe anyone else has.

[rhatdan]

@sujil02 Would you like to take a look at this?

[sujil02]

@sujil02 Would you like to take a look at this?

Sure. I will give it a shot.

[haampie]

Great! Note that docker currently has two different ways in which it supports --cache-from.

The traditional way would be: docker pull img, docker build --cache-from=img

But with buildkit you can do DOCKER_BUILDKIT=1 docker --cache-from=img --build-arg BUILDKIT_INLINE_CACHE=1 and it will lazily download layers without pulling first

[rhatdan]

@ashley-cui PTAL
@sujil02 I don't believe you are still looking at this?

[sujil02]

@ashley-cui PTAL
@sujil02 I don't believe you are still looking at this?

Yeah, I am not. I tried going around this a couple of times but could not get far.

[apollo13]

I am with @mfolnovic on this one, while buildah is usually fast enough it simply cannot beat a cache. Especially for docker files that make clever use of caching by ordering the instructions to utilize the cache as much as possible.

[rhatdan]

@TomSweeneyRedHat @nalind @ashley-cui @QiWang19 Do we have any action on this?

[TomSweeneyRedHat]

@rhatdan way off my radar.

[apollo13]

No takers? :D

[rhatdan]

Not yet @apollo13 Are you interested in working on it?

[apollo13]

Sadly no, my Go knowledge is close to non-existent :(

[rhatdan]

@TomSweeneyRedHat PTAL

[liskin]

Can we perhaps at least make the --cache-from manpage description less confusing? It still reads … Buildah does not currently support caching so this is a NOOP. from the first commit that added it back when there was no caching and it was never updated.

[rhatdan]

Please open a PR to clarify.