Per-account locking

[Daniel Shahaf]

Have you considered stamping a format number somewhere in metadatadir,
and have offlineimap check that number before writing anything into that
dir?

At least that would prevent similar problems going forward (since old
versions would see a too-new format number and abort).

Sebastian Spaeth wrote on Mon, Sep 19, 2011 at 09:47:50 +0200:
> I have now pushed the per-account locks to my 'next' branch. For
> backwards-compatability, the old global lock is still in place, so you
> won't benefit from this goodness. After some releases (next major
> number?) we can then decide to drop support for the old global lock by
> simply reverting commit 0d9565141765b8b23c1c723d325cf494e47cc80d.
> 
> I know that Nicolas would have preferred some cleverer solution where we
> figure out the correct lock to use ourselves. But each time I tried, I
> ran into issues that required more brain than I was willing to use. So
> this is the 2nd-best compromise. Introduce new-style lock now and in a
> few months, we can drop the global one. (Or we could introduce a
> temporary setting that disables the global lock for those who know they
> won't be running an old offlineimap for sure).
> 
> Sebastian
> 
> Commit logs follow:
> commit 0d9565141765b8b23c1c723d325cf494e47cc80d
> Perform legacy global lock in addition to new per-account lock
> 
> We simply lock OfflineImap the same global way that we have always done
> in addition to the previously implemented per-account lock. We can keep
> both systems in parallel and then after a few stable releases, drop the
> old-style global lock. by reverting this patch
> 
> commit 89c705bb2656b8edf028ce569329a012b4515c3e
> init.py: Import OfflineImapError
> 
> The next commit will make use of OfflineImapError but is transient (the
> old-style lock). The commit is supposed to be reverted after a few
> releases. So add the new import in a separate commit, because we might
> need this even when reverting the commit.
> 
> commit c7938dc0819e0a14d1a97e2362e46daa86a7ce85
> Per-account locking
> 
> Previously, we were simply locking offlineimap whenever it was
> running. Howver there is no reason why we shouldn't be able to invoke it
> in parallel, e.g. to synchronize several accounts in one offlineimap
> each.
> 
> This patch implements the locking per-account, so that it is possible to
> sync different accounts at the same time. If in refresh mode, we will
> attempt to loop three times before giving up.
> 
> This also fixes Debian bug #586655



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