[POLL] unexpunge behavior
ken at oceana.com
Tue May 3 10:57:13 EDT 2005
As most of you probably know (or at least *should* know), removing a
message from an IMAP mailstore is a two-step process. First the message
has its \Deleted flag set with the STORE command, then any messages with
this flag are expunged using either the EXPUNGE or CLOSE command. IMAP
itself has no concept of a Trash folder. The Trash folder concept is
something that is layered (some say hacked) on top of the delete+expunge
Since the most expensive part of the expunge process is actually
unlink()ing the message files and rebuilding the cyrus.cache file, in
the 2.3 branch of Cyrus we have implemented something we call "delayed
expunge". With delayed expunge, the cyrus.index records of the expunged
messages are moved to a cyrus.expunge file, but the message files and
cyrus.cache records remain. This has the effect of removing the
messages from the server (no message "exists" without a cyrus.index
record), without all of the expensive overhead so the client gets more
responsive behavior. The actual completion of the expunge is handled
with the cyr_expire utility which is run periodically to unlink() the
message files and rewrite the cyrus.cache file.
In addition to providing better performance for client, the fact that
the message file and corresponding cache record are left behind provides
a window of opportunity for an admin to go back and unexpunge messages
if need be. To this end, I have written an unexpunge utility which
simply restores the cyrus.index record of the expunged message to its
original content. Keeping in mind that removing a message is a two-step
process, the unexpunge utility (by default) only undoes the second step
and reverts the message back to its "deleted but not yet expunged"
state. This means that the \Deleted flag is still set, and depending
upon the IMAP client configuration, may appear with an "X" icon,
strikethrough text, or be hidden entirely. To help such clients, I have
also implemented a -d option for the unexpunge utility which unsets the
\Deleted flag when restoring the message.
So, my question is, what should the *default* behavior of unexpunge be:
A. only unexpunge the message and leave the \Deleted flag set as-is
(only undo the expunge step)?
B. unexpunge the message and unset the \Deleted flag (undo both the
expunge and delete steps)?
I'm of the opinion that A is the correct default behavior and admins can
use the -d option as they see fit, but I will make the default behavior
whatever the consensus ends up being.
Kenneth Murchison Oceana Matrix Ltd.
Software Engineer 21 Princeton Place
716-662-8973 x26 Orchard Park, NY 14127
--PGP Public Key-- http://www.oceana.com/~ken/ksm.pgp
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