On Mon, Dec 17, 2012 at 10:54 PM, Roderich Schupp < roderich.sch...@googlemail.com> wrote:
> On Mon, Dec 17, 2012 at 3:45 PM, Amit Dev <amit...@gmail.com> wrote: > >> We have a perl program packaged into a par. The par is executed and it >> > > By "program packaged into a par" do you mean a standalone executable > created > with "pp -o some.exe script.pl > > " or a .par file created with "pp -p -o some.par script.pl > > " > (that you run with "perl -MPAR=some.par ...")? > It is of the second type, "pp -c -M AnyEvent (and bunch of other -M..) -o some.par script.pl". > For the case of the standalone executable: > > If you run it for the first time (i.e. /tmp/par-USER/cache-DIGEST doesn't > exit), > this cache directory is created and some stuff (a custom perl interpreter, > modules, DLLs, data files) is extracted from the executable into it. > Then the custom perl interpreter is executed, finally running the original > script. > > The next time you run the same executable (as the same user, as the > cache directory is per-user) we see that the cache directory already > exists, > so the extraction phase is skipped and the perl interpreter is executed > right away. > > Actually that's the simplified version - what happens if the first and > second > invocations happen in rapid succession, so that the first is still > extracting stuff > while the second is started? So the actual criterion for "stuff has > completely been > extracted (hence we may skip extraction)" is "does > /tmp/par-USER/cache-DIGEST/inc > exist". If not, acquire some kind of lock, create .../inc, extract stuff > and release the lock. > Acquiring the lock here is implemented as "mkdir .../inc.lock" > (successfully) > and releasing it is "rmdir .../inc.lock" (probably because mkdir is the > only portable > atomic file operation). > > Thanks Roderich. What's happening seems to be that it is failing somewhere in between (since only mkdir happened and rmdir didn't). We are thinking of using PAR_GLOBAL_CLEAN to avoid this whole thing, but curious how it could fail. Some corruption is happening since sometimes files inside the cache (say x.pm) is of 0 bytes.
