Re: Multiple Polipos sharing disk cache

> # What
> I would use two Polipo instances, both using the same disk cache.

Just go ahead, do it.  It's safe; the only issue is that if both Polipi
access the same URL at the same time, one of the two Polipi may
occasionally drop a connection or do some useless work (write out data
to an unlinked file).  Fixing this would require removing the
file-descriptor cache, which would be a shame.

You'll see occasional warnings and broken connections, but no data
should be corrupted.  (This is completely untested, of course.)

> Make Polipo use locking when creating new cache files.
> Make Polipo use locking if changing cache files in-place.

Polipo's update strategy is safe, with the above caveats.  No locks are
needed.  (And I don't like using locks, recall that Polipo is a labour
of love, it's not meant to be actually useful.)

Note that using a lock wouldn't be enough to fix the underlying issue,
which is that the two Polipi won't asynchronously notify each other when
the shared on-disk data changes; this is why you'll see some useless
work being done.

-- Juliusz

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