HOME

Mini Shell 1.0
Current File : //usr/share/doc/dovecot23/wiki/Plugins.Expire.txt
Expire plugin
=============

(See also <autoexpunge> [MailboxSettings.txt] setting, which partially
obsoletes this plugin.)

Typically this plugin is used to optimize expunging old mails from users'
mailboxes. For example:

---%<-------------------------------------------------------------------------
doveadm expunge -A mailbox Trash savedbefore 30d
---%<-------------------------------------------------------------------------

Note that:

 * *This command runs fine even without the expire plugin.* Then it just goes
   through all users rather than those users who have something to actually
   expunge.
 * The plugin actually works for all doveadm mail commands, not just expunge.
   So for testing you could use e.g.'doveadm search -A ...' to see which
   messages it matches.
 * The optimization is done only when -A parameter is used to go through all
   users. If you use -u parameter to separately go through users, the plugin
   does nothing.
 * The optimization is done only when "savedbefore" is used in the search
   query. It's possible to have further restrictions also, but the user
   filtering is based only on the "savedbefore" timestamp.
 * The optimization is done only when the given mailbox or mailboxes match the
   list of expire mailboxes specified in 'plugin { expire* } ' settings.

So the expire plugin's job is to reduce disk I/O when figuring out which users
have work to do. Unless you have thousands of users, you probably shouldn't
bother with this plugin.

Details
-------

When expire plugin is enabled, it keeps track of the "oldest mail's saved
timestamp" for the specified mailboxes. When doveadm command uses "savedbefore"
search key, the timestamps in the database can be used to figure out which
users have matching mails.

Expire plugin tracks/optimizes only "savedbefore" search query, i.e. the date
when message was *saved or copied to the mailbox* (*NOT the time message was
originally received*) while expire plugin was loaded. If mailbox contained
existing messages before the plugin was loaded for the first time, they'll get
expunged eventually when the first message saved/copied after expire plugin was
enabled gets expunged.

The save/copy date may not be exact if it's not cached in
'dovecot.index.cache':

 * mbox: The current lookup time is used and added to cache.
 * maildir: File's ctime is used.
 * dbox: Save/copy time is taken from the dbox file if it exists (it normally
   should), fallbacking to file's ctime if not.

You need to configure a list of mailboxes that are tracked. Mailbox patterns
can contain IMAP LIST command-compatible wildcards:

 * "*" works in a standard way: It matches any number of characters.
 * "%" works by matching any number of characters, but it stops at the
   hierarchy separator. Currently the separator is hardcoded to "/", so it
   doesn't work correctly if you've configured separator to something else
   (e.g. "." is the default for Maildir).

Example configuration
---------------------

Make sure you enable the plugin globally, not just for specific protocols.

---%<-------------------------------------------------------------------------
mail_plugins = $mail_plugins expire

plugin {
  expire = Trash
  expire2 = Trash/*
  expire3 = Spam

  # Enable caching of dict value in dovecot.index file. This significantly
reduces
  # the number of dict lookups. It makes initial testing more confusing though,
so
  # it's better to enable it only after you've verified that the expire plugin
is
  # working as wanted. (v2.2.16+)
  expire_cache = yes
}
---%<-------------------------------------------------------------------------

 * See <Dict.txt> for more information about how to use dict service,
   especially about permission issues.
 * You need to get 'doveadm -A' working using your userdb. See iterate settings
   for <SQL> [AuthDatabase.SQL.txt] and <LDAP> [AuthDatabase.LDAP.txt].

MySQL Backend
-------------

dovecot.conf:

---%<-------------------------------------------------------------------------
plugin {
  expire_dict = proxy::expire
}
dict {
  expire = mysql:/etc/dovecot/dovecot-dict-expire.conf.ext
}
---%<-------------------------------------------------------------------------

Create the table like this:

---%<-------------------------------------------------------------------------
CREATE TABLE expires (
  username varchar(75) not null,
  mailbox varchar(255) not null,
  expire_stamp integer not null,
  primary key (username, mailbox)
);
---%<-------------------------------------------------------------------------

dovecot-dict-expire.conf.ext:

---%<-------------------------------------------------------------------------
connect = host=localhost dbname=mails user=sqluser password=sqlpass

map {
  pattern = shared/expire/$user/$mailbox
  table = expires
  value_field = expire_stamp

  fields {
    username = $user
    mailbox = $mailbox
  }
}
---%<-------------------------------------------------------------------------

PostgreSQL Backend
------------------

Like MySQL configuration above, but you'll also need to create a trigger:

---%<-------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION merge_expires() RETURNS TRIGGER AS $$
BEGIN
  UPDATE expires SET expire_stamp = NEW.expire_stamp
    WHERE username = NEW.username AND mailbox = NEW.mailbox;
  IF FOUND THEN
    RETURN NULL;
  ELSE
    RETURN NEW;
  END IF;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER mergeexpires BEFORE INSERT ON expires
   FOR EACH ROW EXECUTE PROCEDURE merge_expires();
---%<-------------------------------------------------------------------------

SQLite Backend
--------------

Like MySQL configuration above, but you'll also need to create a trigger:

---%<-------------------------------------------------------------------------
CREATE TRIGGER mergeexpires BEFORE INSERT ON expires FOR EACH ROW
BEGIN
        UPDATE expires SET expire_stamp=NEW.expire_stamp
                WHERE username = NEW.username AND mailbox = NEW.mailbox;
        SELECT raise(ignore)
                WHERE (SELECT 1 FROM expires WHERE username = NEW.username AND
mailbox = NEW.mailbox) IS NOT NULL;
END;
---%<-------------------------------------------------------------------------

Vpopmail (+MySQL)
-----------------

Configure expire plugin like MySQL configuration. From here, there are two
cases:

If you are using the mysql database for authentication directly, you only need
to make iterate work for <MySQL> [AuthDatabase.SQL.txt].

When using Vpopmail backend, doveadm -A won't work. To be able to use the
expire database, you can use a bash script like this:

---%<-------------------------------------------------------------------------
#!/bin/bash

# SQL connection data
HOST="localhost"
USER="dovecot"
PWD="yourpassword"
DBNAME="vpopmail"
TBLNAME="expires"
# expunge messages older than this (days)
TTL=30

expiredsql=`cat <<EOF
  USE $DBNAME;
  SELECT CONCAT(username, "~", mailbox)
  FROM $TBLNAME
  WHERE expire_stamp>0 AND expire_stamp<UNIX_TIMESTAMP()-86400*$TTL;
EOF`

for row in `echo "$expiredsql" | mysql -h $HOST -u $USER -p$PWD -N`; do
  username=`echo $row | cut -d"~" -f1`
  mailbox=`echo $row | cut -d"~" -f2-`

  # Check if mailbox name is empty. Just in case.
  if [ -n $mailbox ]; then
        echo "Expunging: "$row
        doveadm expunge -u $username mailbox "$mailbox" savedbefore $TTL"d"
  fi
done
---%<-------------------------------------------------------------------------

Example #1 timeline
-------------------

FIXME: expire-tool no longer exists, update these examples. Let's say Trash is
configured to expire in 7 days and today is 2009-07-10. Initially the database
and the Trash mailbox is empty.

User moves the first message to Trash. The expires table is updated:

---%<-------------------------------------------------------------------------
mysql> select mailbox, from_unixtime(expire_stamp), username from expires;
+---------+-----------------------------+----------+
| mailbox | from_unixtime(expire_stamp) | username |
+---------+-----------------------------+----------+
| Trash   | 2009-07-17 15:57:36         | tss      |
+---------+-----------------------------+----------+
---%<-------------------------------------------------------------------------

The expire_stamp contains the date when expire-tool will look into that mailbox
and try to find messages to expunge. Until then it skips the mailbox.

A day later user moves another message to Trash. The expire_stamp isn't
updated, because the second message's save date is newer than the first one's.
Checking Trash's contents via IMAP you can see something like:

---%<-------------------------------------------------------------------------
1 fetch 1:* (internaldate x-savedate)
* 1 FETCH (INTERNALDATE "16-Dec-2008 09:52:38 -0500" X-SAVEDATE "10-Jul-2009
15:57:36 -0400")
* 2 FETCH (INTERNALDATE "29-Jun-2003 23:20:09 -0400" X-SAVEDATE "11-Jul-2009
16:03:11 -0400")
1 OK Fetch completed.
---%<-------------------------------------------------------------------------

Note how the message's INTERNALDATE (received date) can be very old compared to
the save date. Now, running expire-tool --test:

---%<-------------------------------------------------------------------------
Info: tss/Trash: stop, expire time in future: Fri Jul 17 15:57:36 2009
---%<-------------------------------------------------------------------------

So it does nothing, because the expire time is in future. Fast forward 6 more
days into future. Running expire-tool --test:

---%<-------------------------------------------------------------------------
Info: tss/Trash: seq=1 uid=1: Expunge
Info: tss/Trash: timestamp 1247860656 (Fri Jul 17 15:57:36 2009) -> 1247947391
(Sat Jul 18 16:03:11 2009)
---%<-------------------------------------------------------------------------

The first message would be expunged and the second message's timestamp would
become the new expire_stamp in database. After running expire-tool without
--test, the database is updated:

---%<-------------------------------------------------------------------------
mysql> select mailbox, from_unixtime(expire_stamp), username from expires;
+---------+-----------------------------+----------+
| mailbox | from_unixtime(expire_stamp) | username |
+---------+-----------------------------+----------+
| Trash   | 2009-07-18 16:03:11         | tss      |
+---------+-----------------------------+----------+
---%<-------------------------------------------------------------------------

Also you can see the first message has been expunged from Trash:

---%<-------------------------------------------------------------------------
2 fetch 1:* (internaldate x-savedate)
* 1 FETCH (INTERNALDATE "29-Jun-2003 23:20:09 -0400" X-SAVEDATE "11-Jul-2009
16:03:11 -0400")
2 OK Fetch completed.
---%<-------------------------------------------------------------------------

Example #2 timeline
-------------------

Again you have Trash configured for 7 days, but this time you have an existing
message there before expire plugin has been enabled. Initially the expire
database is empty. Today is 2009-07-20.

---%<-------------------------------------------------------------------------
1 fetch 1:* (internaldate x-savedate)
* 1 FETCH (INTERNALDATE "29-Jun-2003 23:20:09 -0400" X-SAVEDATE "11-Jul-2009
16:03:11 -0400")
1 OK Fetch completed.
---%<-------------------------------------------------------------------------

If you run expire-tool, you'll notice that it does nothing for the mailbox.
There's nothing in expire database, so expire-tool doesn't even mention it when
running with --test.

After user moves the first message to Trash, the database gets updated:

---%<-------------------------------------------------------------------------
mysql> select mailbox, from_unixtime(expire_stamp), username from expires;
+---------+-----------------------------+----------+
| mailbox | from_unixtime(expire_stamp) | username |
+---------+-----------------------------+----------+
| Trash   | 2009-07-27 16:32:11         | tss      |
+---------+-----------------------------+----------+
---%<-------------------------------------------------------------------------

The messages in Trash are:

---%<-------------------------------------------------------------------------
2 fetch 1:* (internaldate x-savedate)
* 1 FETCH (INTERNALDATE "29-Jun-2003 23:20:09 -0400" X-SAVEDATE "11-Jul-2009
16:03:11 -0400")
* 2 FETCH (INTERNALDATE "16-Dec-2002 11:02:39 -0500" X-SAVEDATE "20-Jul-2009
16:32:11 -0400")
2 OK Fetch completed.
---%<-------------------------------------------------------------------------

So the first message should be expiring already, right? No. It doesn't because
the timestamp in database is still in future. expire-tool --test says:

---%<-------------------------------------------------------------------------
Info: tss/Trash: stop, expire time in future: Mon Jul 27 16:32:11 2009
---%<-------------------------------------------------------------------------

OK, let's see what happens when we finally reach July 27th:

---%<-------------------------------------------------------------------------
Info: tss/Trash: seq=1 uid=3: Expunge
Info: tss/Trash: seq=2 uid=4: Expunge
Info: tss/Trash: no messages left
---%<-------------------------------------------------------------------------

They both got expunged! The expire database's timestamp simply tells
expire-tool when to start looking into messages in that mailbox. After that
expire-tool looks at the actual save dates and figures out which messages
exactly need to be expunged.

After running expire-tool without --test you'll see that the Trash mailbox is
empty and the database row is deleted.

(This file was created from the wiki on 2019-06-19 12:42)