Build error with folly and fmt about cachelib

[igchor]

To Meta team: could you please share what is the rationale behind fetching the latest dependencies on every build? Did you consider setting some specific version of each dependency in build-package.sh (e.g. to the latest release) and just updating them when necessary?

[agordon]

Hello @igchor ,

We can divide the dependencies into two groups: everything before folly (i.e. packages which do not depend on folly: zstd, googlelog, googletest, googleflags, fmt, sparsemap), then folly and all packages that do depend on it (folly, fizz, wangle, fbthrift) .

folly itself does not have a "release" or "stable" version. It is always being updated.
folly is added as git submodule to cachelib (like in many other projects which use folly). The difference is: other projects can decide to pin the folly git-submodule to a specific commit, and leave it as-is for a long time (effectively making it "stable").

But cachelib is a Facebook/Meta project, and the internal code base always tracks the latest folly build (observe all the commits at https://github.com/facebook/CacheLib/commits/main which just say "updating submodules" - those are automatic).

And so, when you update cachelib (with git pull) you also update the folly submodule commit version. Then you need to rebuild folly. and then you need to rebuild the downstream packages (fizz/wangle/fbthrift) which depend on folly.

For the other packages, you'll notice we do use a specific git tag or branch ( e.g https://github.com/facebook/CacheLib/blob/main/contrib/build-package.sh#L120 ). So those, even though we do a "git pull", it should remain in the same commit, and a make should be very fast.

I notice fmt is an exception - not pinned to a specific git tag or revision - likely an omission that can be fixed.

Hope this answered your question.
regards,
-assaf

[ankita-shankar]

For fmt, the build error is being caused by, this commit: fmtlib/fmt@3a951a6
I think there needs to be either changes made in Cachelib to fix this, or make it point to one of the previous version of fmt.

[vereimyst]

Not sure if this was already cleared up (I'm assuming not since I ran into the same issue when reinstalling Cachelib today), but I managed to get around the folly build issue by doing ./contrib/build-package.sh -d. Definitely doesn't address the issue within the build script though...
Still in the midst of installation, so there may or may not be further issues down the line that I haven't encountered yet doing it this way.