[MERGE] Faster LocalTransport.put() and append() methods.

[Robert Collins]

On Wed, 2006-06-14 at 13:36 +1000, Martin Pool wrote:


> Since you're creating the file with O_EXCL I don't see any need to  
> include the PID.  Instead, if that fails with EEXIST then just e.g.  
> add a sequence number and try again.

O_EXCL is documented as broken on NFS. if use a static suffix - i.e.
filename + '.bzrtmp', if someone has a file that looks like that, we may
overwrite it unintentionally - *depending on the manner of the
brokenness for NFS*.

If its 'race conditions with two clients writing the same file' broken -
then I'm happy to remove the pid. If its 'O_EXCL is simply ignored on
some implementations' then I think the pid is a not-too-bad price to
pay.

> To clarify - the point of chmod is to make sure that differing umasks  
> don't lead to bzrdirs with inconsistent permissions between their  
> files.  (e.g. most are 0660, some are 0600.)
> 
> >> I would be happy with that. Problem #1 is that I don't know of any  
> >> way
> >> to determine the current umask without setting it. (os.umask() will
> >> return the old umask, but only after you set a new one).
> >
> > mask = os.umask(0)
> > os.umask(mask)
> 
> If we're going to do that then perhaps we can just reset our umask  
> entirely while updating the repository from a try/finally block.   
> That is what we're logically trying to achieve.  The main problem is  
> if we need to interleave access to different objects that should get  
> different permissions.

And thread safety may be an issue too. I think calculating the umask
when the module is first used, and then chmodding IFF its needed is a
reasonable compromise.

Rob

-- 
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