Hi all,
I have a (possibly silly) idea for my set-up that basically involves mbsync
running continuously as a daemon, in the way that IMAP was designed to do. I
think this has already been discussed on this list (see below [0][1][2]), but
AFAIK it's not actually possible yet. So I'm basically asking
a) are there existing tools available to do this? (I do not have shell access
to the remote servers)
b) if not, is anyone working on it?
c) if not, is it something you might consider adding in a later release, or
accepting a patch for?
d) for any feedback anyone has on this.
The setup I have now uses mbsync run every few minutes (5 at the moment, poor
server people :P) to re-synchronise mailboxes. This is done for about six
different mail accounts from various providers (several are Gmail accounts).
This obviously has the problem that it can take up to five and a half minutes
for me to be aware that new mail has arrived (the periodic check once the
initial sync has been done takes about 30-40 seconds for the lot).
Ideally, I'd have mbsync run as a daemon, make a connection to the remote IMAP
server and then sit there watching both the remote IMAP folders and the local
maildirs. IMAP push notifications would trigger it to download changes and
sieve them into my local copy; local modifications would trigger it to upload
the changes. It doesn't seem /totally/ ridiculous - after all, this is
more-or-less what clients such as Thunderbird do.
Two prior postings to the list I've found are [0] and [1]. [0] includes a "I've
thought about it but not implemented it" from 2007; [1] contains an FYI
regarding mswatch from 2014, which as I've pointed out isn't going to cut it as
I don't have shell access to the servers. In any case, IMAP is already capable
of pushing notifications to clients, so a separate channel is technically
unnecessary.
I also found a TODO entry, which pointed me to a further post [2] and another
RFC [3].
The way I'd see this being possible would be
- for remote changes, using the full functionality of IMAP to receive
notifications pushed from the server in order to trigger a sync. Wikipedia[4]
suggests that this is possible, and a skim of the RFC doesn't rule it out at
least[5][6][3]. Presumably you might need an extra couple of lines in the
mbsync config (Subscribe etc.), if I've divined the use of SUBSCRIBEd
mailboxes correctly.
- for local changes, monitoring the local maildir with file descriptors (as far
as I can tell, mbsync is written for UNIX only, so inotify or dnotify both
appear at first read to be appropriate here (though [7] suggests it may be
impracticable for large maildirs or large numbers of accounts)). An
alternative which'd possibly be better from an engineering point of view is
libev[8] (though mbsync doesn't already use it, so). I've not used these or
similar kernel subsystems before, though, so feedback is much appreciated on
that.
So the crux:
a) are there existing tools available to do this (I do not have shell access
to the remote servers)?
b) if not, is anyone working on it?
c) if not, is it something you might consider adding in a later release, or
accepting a patch for?
d) any other feedback is welcome.
If the answer to (b) or (c) is yes, I am able to provide some help ^.^.
Best wishes,
allicoder
[0] http://sourceforge.net/p/isync/mailman/message/1473227/
[1] http://sourceforge.net/p/isync/mailman/message/32989263/
[2] http://sourceforge.net/p/isync/mailman/message/30353955/
[3] http://tools.ietf.org/html/rfc5465
[4]
https://en.wikipedia.org/wiki/Internet_Message_Access_Protocol#Connected_and_disconnected_modes_of_operation
[5] https://tools.ietf.org/html/rfc3501#section-5.2
[6] https://tools.ietf.org/html/rfc3501#section-7.4.2
[7] http://stefan.buettcher.org/cs/fschange/index.html
[8] http://software.schmorp.de/pkg/libev.html
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