Cache dir / volume

[viceice]

We should support an optional cache dir /volume to cache downloads, so we can mount a host volume / docker volume and reuse downloads to speedup later runs.

So Cache will be enabled if BUILDPACK_CACHE points to an existing folder.

[Chumper]

This would be high on my priority list, so that I can move to k8s with persistent volumes.
This would require an adjustment on all tools correct?

My idea for tool installation is:

• check if tool is in cache (e.g. go${GOLANG_FILE_VERSION}.linux-amd64.tar.gz)
• If not, download it into the cache folder
• Extract the binary from the cache folder

That would require all tools to download their dependencies into the cache.
Or more abstract we create a download method that tools use.
Internally we will check the cache first and download the file if needed then return it.

[viceice]

Sounds good, but cache should only be used when explicit enabled. But feel free to open a draft PR for a single tool, so we can go forward on this.

[rarkins]

Is your primary concern bandwidth, or something else?

[Chumper]

yeah, my primary concern is bandwith, especially because we have a high number of javascript, python and go repositories.
If we would download the tools every time, that would be a bad idea.
We as a company already create a lot of traffic for certain package registries, so I am trying to cache as much as possible.

It is not in the scale of the open source app you maintain, but its already a bit with around 500 onboarded repos atm.