[Tracker] [PATCH] "Daemonize" metadata extractor

[Carlos Garnacho <carlos imendio com>]

Hi!,

I've attached a patch in bug #519337 to keep the extractor alive between
operations. This greatly improves performance, as it avoids having to
spawn/initialize the extractor constantly for each new file. With the
patch, the extractor shuts down by itself after 30 seconds of
inactivity, any testing is appreciated.

Besides, I've been thinking a bit in this subject. Right now trackerd
waits synchronously for the metadata extractor output (and the same
happens for thumbnailing, even when such data isn't immediately
necessary), so only 1 file is processed at the same time. 

Has there been any thinking/work on making that parallelizable? I'm sure
there'd be performance improvements if there was a pool of extractors
which asynchronously processed a queue of filenames.

Regards,
   Carlos