Clusters, grids and Squeak

Tim Rowledge tim at sumeru.stanford.edu
Wed Apr 20 17:41:24 UTC 2005


"Bruce O'Neel" <edoneel at sdf.lonestar.org> wrote:

> On Wed, Apr 20, 2005 at 09:04:45PM +1200, Michael van der Gulik wrote:
> 
> > Be carefull not to modify any code from any of those headless instances 
> > - the squeak.sources file will end up corrupted. There is no 
> > multi-threaded protection on it. (I learned this the hard way.)
> > 
> 
> I would expect the .sources file to be read/only.
It's certainly supposed to be. It is opened as readonly in FileDirectory
class>openSources:forImage: So there shouldn't be any mangling of the suorce
file...

>  The .changes file
> on the other hand gets quite messed up when you have multiple
> instances pounding on the same .changes file.
Exactly. It is of neccessity opened read/write (several times in fact, as I
used to complain of regularly) an nominally the logging of changes is done by
seekign to the end of the file and writing. This does no good if two or more
writing processes are going on at the same time (see, I managed to link it to
the native threads thread!) you get the classic problem of shared resources.

I think it is pretty obvious that in any production use of a developed
application that there would not be much of as problem with the changes file;
lots of other parallel issues would be driving you to hairlessness before that
one got noticed.


tim
--
Tim Rowledge, tim at sumeru.stanford.edu, http://sumeru.stanford.edu/tim
Software is mind work.  Having the right frame of mind is essential.



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