On 30-05-14 18:13, Andrea Brancatelli wrote:
> What are the pro and cons of enabling (or disabling) IMAP idle?
It depends on the dbmail version. For 2.x each IDLE connection implied a
dedicated process (fork) plus a dedicated database connection. This
didn't scale too well.
In 3.x IDLE scales *very* well. Client connections are kept in an event
state-machine with very little overhead, and database connections are
shared and pulled from a small pool.
As to data transfer:
- without IDLE (and on dbmail < 3.2) the client has to fetch the flags
on *all* messages in a watched mail folder regularly.
for dbmail >= 3.2 modern clients won't have to do that. They can simply
issue a QRESYNC and get only updates for modified messages (esp flags).
- with IDLE mail clients automatically receive flag updates if and when
they happen.
In dbmail-3.1 a modification sequence is kept per mailbox, so dbmail can
quickly determine if and when a mailbox had any messages modified since
the last known mailbox sequence. In dbmail-3.2 this has been further
improved (to support QRESYNC) by adding a sequence value to the messages
table as well. This value is updated simultaneously with tbe mailbox
sequence. Doing that we can quickly query for only those messages that
were modified since the last known sequence value.
So: for dbmail-3 there is no downside to using IDLE. For dbmail-3.2 with
QRESYNC the advantages of IDLE will be very limited, but only for those
clients that support QRESYNC. For clients that don't: they are still
well off using IDLE.
> I have a problem with Mac OS X mail falling asleep with the IMAP
> session. You press "fetch mail", nothing happens. You close mail and
> reopen it and dozens of mail appear. Maybe that could be a
> workaround?
That sounds like a synchronization bug. Which dbmail version are you using?
--
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Paul J Stevens pjstevns @ gmail, twitter, github, linkedin
www.nfg.nl/[email protected]/+31.85.877.99.97
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