[OE-core] sharing DL_DIR?

[Rich Pixley]

What happens if two separate bitbake invocations both simultaneously 
attempt to download the same file?

--rich

On 2/22/12 15:41 , Christopher Larson wrote:
> I share it as well. I don't see locks being a big issue for most 
> things, as the worst case is a re-download, not use of a corrupt or 
> incomplete file, due to the completion stamps.
>
> -- 
> Christopher Larson
>
> On Wednesday, February 22, 2012 at 4:39 PM, Tom King wrote:
>
>> I have a single downloads directory with symlinks for every target 
>> build I have to that directory.  As long as I have the source already 
>> in there I don't fetch  it again
>>
>> Tom
>>
>> On Wed, Feb 22, 2012 at 1:33 PM, Rich Pixley <rich.pixley at palm.com 
>> <mailto:rich.pixley at palm.com>> wrote:
>>> Is it reasonable to expect to share DL_DIR between multiple 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?
>>>
>>> Or must each build download it's own copies of every component?
>>>
>>> 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.
>>>
>>> --rich
>>>
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>>
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