break down pull latency and unpack latency

[fahedouch]

Discussed in https://github.com/containerd/nerdctl/discussions/1570

^{Originally posted by qi0523 November 30, 2022} How to break down pull latency and unpack latency when using nerdctl pull ?

more details

[djdongjin]

I think it will need some changes to how nerdctl pull images (use client.Pull with Unpack option).

This might be the related code path:

add unpack option and call pull: link

call containerd client.Pull/Fetch to get the image (w or w/o unpack): link

Instead of client.Pull, it might require something like this to separate pull and unpack (similar to ctr):

client.Fetch()
i := containerd.NewImageWithPlatform(client, img, platforms.Only(platform))
err = i.Unpack(ctx, context.String("snapshotter"))

[tushar5526]

This looks interesting to me. Though I would have to play with ctr tool a bit to understand the requirements here first.