Some future Dovecot version will have "imap-idle" processes where IDLEing IMAP connections get moved, so the system wouldn't waste so much memory for all the IDLEing imap processes. A week ago I thought I'd see how easy it would be to implement this. I got a basic proof of concept working as a "X-STATE" command.

Save the state:

a x-state

• STATE AQDLW45QdwAAAAMAAABuAQAAAAAAAFAcffYAPHnpFctbjlDbYQAAcEmzCwAA a OK State exported.

Restore the state:

b x-state AQDLW45QdwAAAAMAAABuAQAAAAAAAFAcffYAPHnpFctbjlDbYQAAcEmzCwAA b OK State imported.

This could also be used to implement quick session state restoring for webmails (as suggested by Michael Slusarz).

For getting the imap-idle process there would have to be code that:

• triggers the session saving when process is IDLEing
• figures out what filesystem paths the imap-idle should be looking at (i.e. paths to selected mailbox's dovecot.index.log file and maybe for e.g. maildir new/)
• send the session state string, paths and imap connection fd to imap-idle process via UNIX socket
• implement the actual imap-idle process
• implement a way for imap-idle process to send back the state and connection fd to restore the imap process

The patch is ugly and still missing many things. Anyway I thought I'd include it here just in case someone was really eager to continue implementing it. :) I'm not sure when I'll have time for it.

A full patch would probably have to have some session_save()/session_restore() functions in lib-storage API. But a quick and dirty way is possible to implement for v2.1 as well, as long as some IMAP extensions aren't used (most importantly rfc5267).