Description of problem:
a)
Idled method is used only first time in imapd process live. Then poll method is used.
After starting, imapd process creates own unix socket {configdirectory}/socket/idle.<pid> (by call idle_enabled()). After e-mail client connect to it and issue IDLE command, imapd waits for notification of new mail (form lmtpd for example). 
After new mail arrives, lmtpd notifies imapd about it and imapd immediately notifies client. Ok so far.

But then imapd calls idle_done() which closes (and removes) {configdirectory}/socket/idle.<pid>. This is problem.
After client issue IDLE command again, imapd can't communicate with closed socket and use "poll" method to check updates to mailbox.
It means, client will be notified about next new mail after (max) 'imapidlepoll' time (default 60s).

b) 
In {configdirectory}/socket/ remains thousands of idle.<pid> files. If pop3d proces is started, it creates own idle.<pid> file (by call idle_enabled()), but this file is never removed. Neither after terminating of pop3d. 
Other cyrus-imapd processess (imapd, lmtpd) leaves idle.<pid> too. Only situation, where idle.<pid> is removed is described in (a).



Version-Release number of selected component (if applicable):
cyrus-imapd-2.3.16-6.el6_2.5

How reproducible:
Easy

Steps to Reproduce:
Will test on mailbox name 'johndoe'. /etc/imapd.conf:imapidlepoll setting is default (60s).

1) Clean idle.* sockets and restart.
$ service cyrus-imapd stop
$ rm /var/lib/imap/socket/idle.* -f
$ service cyrus-imapd start

2) Enable protocol debugging for johndoe.
$ cd /var/lib/imap/log/
$ mkdir johndoe
$ chown cyrus

3) Connect to imap by email-client (I use Mozilla Thunderbird)
$ tail -f johndoe/*
here you will see, Thunderbird issue IDLE command
$ ls -l /var/lib/imap/socket/idle.*
here you will see socket of our imapd process

4) Send first mail to johndoe's mailbox.
$ echo test | mail johndoe
at tail screen you will see immediately notification about new mail (and this mail is downloaded to Thunderbird). Ok so far.
$ ls -l /var/lib/imap/socket/idle.*
Here you will see socket of our imapd process disapeared.

5) Send second mail...
$ echo test | mail johndoe
at tail screen you will see notification about new mail appears after random delay (0 - 60s) because poll not idled.

6) Terminate cyrus-imapd and count imapd.* leaved
$ service cyrus-imapd stop
$ ls -l /var/lib/imap/socket/imap.*


Actual results:
a) after first IDLE notification using idled, next is deferred by poll mechanism
b) many imap.* files remains

Expected results:
a) every time use idled IDLE notifications 
b) at {configdirectory}/socket/ must be only idle.* sockets of running process, not of terminated

Additional info:
This problem was involved by idle* patch (last patch in cyrus-imapd-2.3.16-6.el6_2.5). Before that, processes communicate via single {configdirectory}/socket/idle socket. 

Thank you
Michal Michaláč