[OE-core] sharing DL_DIR?

[Saul Wold]

On 02/22/2012 03:33 PM, Rich Pixley wrote:
> Is it reasonable to expect to share DL_DIR between multiple builds?
>
Absolutely, We share DL_DIR via NFS across multiple machines and builds.

> That is, are downloads properly locked so that multiple concurrent
> downloads of the same file won't collide? And if so, are they NFS safe
> locks?
>
Yes, as far as I know.

> Or must each build download it's own copies of every component?
>
No need.

> I ask because our, (Palm), branch has been, but it's a bit of a nuisance
> to pick a suitable locking mechanism that is both functional and performant.
>
>   * Flock/lockf aren't reliably supported in heterogeneous environments.
>   * The old lockfiles don't work over NFS. Lock directories apparently
>     do, but trying to clean these up after interruptions or failures is
>     a losing battle so if we do use these, we end up with orphan locks
>     periodically.
>   * With NFS as a possibility, we can't assume any kernel local IPC
>     mechanism, so sysV ipc is out.
>   * It seems like a pretty huge overhead to try to create any sort of
>     zeroconf overhead.
>
> Our solution so far has been to use NFS lock directories for multiple
> machine builds and flock/lockf for single machine builds. This mostly
> works, though it's not ideal, and it's significantly faster than
> downloading/copying all of the component source multiple times even over
> local mirrors.
>
I think we are using a very basic locking mechism that creates the 
lockfile and a donefile when complete.  It seems to work well enough.

Sau!

> --rich
>
>
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