I have a few questions about the file system stuff: • what is the difference between what goes into

~/.cache/pants/named_caches/pex_root

and

~/.pex/

? • is there a way to set where

named_caches/

,

lmdb_store

go? e.g. somewhere on NFS

~/.pex

is when you use Pex outside of Pants.

~/.cache/pants/named_caches/pex_root

is the same thing, but isolated.

is there a way to set where

Yes, I really need to finish https://www.pantsbuild.org/docs/troubleshooting#how-to-change-your-cache-directory. Change

named_caches_dir

and

local_store_dir

in the

[GLOBAL]

scope

great, thank you

Documented at https://www.pantsbuild.org/docs/troubleshooting#how-to-change-your-cache-directory. Any suggestions appreciated

thank you @hundreds-father-404 this looks great and concise, I would still have a couple of related questions: 1. why

~/.pex

is populated when running pants? i don't know why it appears there when pants already uses

named_caches

2. what happens if multiple concurrent builds point to the same

lmdb_store

/

named_caches

say somewhere on NFS

1. I wouldn’t expect you to have that folder from running Pants, and it’s a bug if you do. Have you ever run Pex directly? Like

pip install pex

, then

pex -o my_pex req1 req2

?. 2. That should be safe afaict.

lmdb_store

uses the Lightning Memory-Mapped Database scheme: https://en.wikipedia.org/wiki/Lightning_Memory-Mapped_Database, and can handle multiple projects writing at the same time.

named_caches

is exclusively append-only caches, i.e. that avoid overwriting anything. (This is why it’s so tricky for us to leverage MyPy’s cache in a safe way, which mutates) 3. I think

$PANTS_HOME

is only used by the

./pants

script to determine where to put

~/.cache/pants/setup

. Perhaps we should rename it to something like

PANTS_SETUP_CACHE

.

Great answer, thank you @hundreds-father-404 Yes, that's what I observed PANTS_HOME does. I just validated again: 1.

rm -rf ~/.pex/

2.

du -sh ~/.pex/

-> no such file or directory 3.

./pants fmt ::

• initialising pantsd • finding interpreter to satisfy constraints • run isort, docformatter (without building isort, docformatter) 4.

du -sh ~/.pex/

-> 17M

https://github.com/pantsbuild/setup/pull/87 to rename

PANTS_HOME

that was really really fast!! Thank you @hundreds-father-404