Consider implementing a "remote cache" in the style of Bazel

[andreabedini]

Describe the feature request

Bazel implements a remote caching through
a HTTP protocol that is simple enough to be used with many different
backends.

The protocol is basically a
content-addressed blob store, accessed with GET/PUT requests.

cabal-install could use the same protocol to support a remotely-cached cabal
store. This could be very useful in CI setups.

I am perfectly aware that there are impurities in the hash key used in the
store, especially with respect to external dependencies. I don't think this
invalidates the utility of this feature.

After a first look, the most invasive change would be to generalise
StoreDirLayout
to be able to perform network IO, perhaps separating it from
CabalDirLayout.
The store logic itself seems to require minor changes, the most notable one
being replacing
getStoreEntries
because we will not be able to traverse the remote cache.

[michaelpj]

It sounds like this would obsolete https://github.com/haskell-works/cabal-cache ?

[andreabedini]

It sounds like this would obsolete https://github.com/haskell-works/cabal-cache ?

I would say that the existence of cabal-cache proves that this is desierable feature.

The README of cabal-cache mentions #4097, which is worthy of note here too.

[TeofilC]

This looks like a duplicate of #5582, which also suggests the bazel protocol

[andreabedini]

Thanks @TeofilC 🤦
Closing as duplicate.