[Dovecot] Maildir locking by LDA of dovecot
Hi all!
First of all, I want ti thank the whole Dovecot community (developers for developing and fast responses, users for populating and responses too). Dovecot is a really good and fast IMAP server - it serves near 3000 in our installation.
Now I have a problem and request community's help its resolving;) Dovecot version: 1.0.13, compiled with vpopmail support. I have an account spam@domain.com (:-), in which we put all our spam (we gather statistic later). There can be 10 and more delivery attempts in a second to maildir of this account during the spam attacks on our server. The queue of our server can grow up to 20k messages, and all of these messages are sent to spam@domain.com. I found a lot of such strings in dovecot.log file during such DoS attack:
dovecot.log:deliver(spam@domain.com): May 16 04:18:48 Info: msgid=01c8b6da$a8bacf80$b7af2abe@sale: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:18:59 Info: msgid=6611811842.20080516012444@poiusadfhnvxzmdiasdasgkhlsdkfg.com: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:20:06 Info: msgid=01c8b6a8$7b552e00$a0a4034c@sale: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:20:14 Info: msgid=360825920.32055246029506@mirgames.ru: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:20:50 Info: msgid=01c8b6b1$0df9cb00$cc36dfc9@tek2: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:21:00 Info: msgid=087901c7ca2d$ef272640$1e01a8c0@telefonia.InterCable.net: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:21:01 Info: msgid=000701c8b6d2$01ff999f$c491aca7@snoueiij: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:22:32 Info: msgid=000801c8b69b$060c0230$3cd8a4b7@cpbvlrx: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:22:45 Info: msgid=000801c8b6a5$04ba6412$9910848d@aldldr: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:22:45 Info: msgid=031401c772e2$adc5be40$1e01a8c0@mtu-net.ru: save failed to INBOX: Timeout while waiting for lock dovecot.log:deliver(spam@domain.com): May 16 04:23:08 Info: msgid=01c8b6db$0222fe80$b7af2abe@info: save failed to INBOX: Timeout while waiting for lock
What can I do for resolving this locks? The queue of my server becomes really big! May be, while looking into uidlist file, can dovecot LDA lock it? And other deliver processes can't open it and wait for him?
$ dovecot --version 1.0.13
# dovecot -n # 1.0.13: /etc/dovecot.conf log_path: /var/log/dovecot.log protocols: imap pop3 ssl_disable: yes login_dir: /var/run/dovecot/login login_executable(default): /usr/libexec/dovecot/imap-login login_executable(imap): /usr/libexec/dovecot/imap-login login_executable(pop3): /usr/libexec/dovecot/pop3-login login_greeting: Server is ready. login_process_per_connection: no login_greeting_capability(default): yes login_greeting_capability(imap): yes login_greeting_capability(pop3): no login_max_connections: 1024 first_valid_uid: 39 last_valid_uid: 39 first_valid_gid: 39 last_valid_gid: 39 fsync_disable: yes maildir_copy_with_hardlinks: yes mail_executable(default): /usr/libexec/dovecot/imap mail_executable(imap): /usr/libexec/dovecot/imap mail_executable(pop3): /usr/libexec/dovecot/pop3 mail_plugins(default): quota imap_quota mail_plugins(imap): quota imap_quota mail_plugins(pop3): quota mail_plugin_dir(default): /usr/lib/dovecot/imap mail_plugin_dir(imap): /usr/lib/dovecot/imap mail_plugin_dir(pop3): /usr/lib/dovecot/pop3 auth default: mechanisms: plain login cram-md5 default_realm: tversu.ru cache_size: 10240 user: vpopmail username_format: %Lu passdb: driver: vpopmail args: cache_key=%u dovecot userdb: driver: vpopmail socket: type: listen client: path: /var/spool/postfix/private/auth mode: 438 user: postfix group: postfix master: path: /var/run/dovecot/auth-master mode: 438 plugin: quota: maildir:ignore=Trash
WBR, Mike Grozak, TvSU IC
On 5/22/2008, Mike Grozak (mike@tversu.ru) wrote:
First of all, I want ti thank the whole Dovecot community (developers for developing and fast responses, users for populating and responses too). Dovecot is a really good and fast IMAP server - it serves near 3000 in our installation.
What filesystem is this on?
--
Best regards,
Charles
Charles Marcus wrote:
On 5/22/2008, Mike Grozak (mike@tversu.ru) wrote:
First of all, I want ti thank the whole Dovecot community (developers for developing and fast responses, users for populating and responses too). Dovecot is a really good and fast IMAP server - it serves near 3000 in our installation.
What filesystem is this on? ext3.
How can I escape dovecot-uidlist locking? it really locks my system!
WBR, Mike Grozak, TvSU IC
On 5/22/2008 7:06 AM, Mike Grozak wrote:
First of all, I want ti thank the whole Dovecot community (developers for developing and fast responses, users for populating and responses too). Dovecot is a really good and fast IMAP server - it serves near 3000 in our installation.
What filesystem is this on?
ext3.
How can I escape dovecot-uidlist locking? it really locks my system!
Have you read closely this page?
http://wiki.dovecot.org/MailboxFormat/Maildir
It discusses how to properly use dovecot-uidlist.lock
For example:
"The dovecot-uidlist file doesn't need to be locked for reading. When writing dovecot-uidlist.lock file needs to be created. The dovecot-uidlist file must never be directly modified, it can only be replaced with rename() call."
and
"Because Dovecot uses its own non-standard locking (dovecot-uidlist.lock dotlock file), other MUAs accessing the maildir don't support it. This means that if another MUA is updating messages' flags or expunging messages, Dovecot might temporarily lose some message. After the next sync when it finds it again, an error message may be written to log and the message will receive a new UID."
It may be a vpopmail issue, but I don't that...
Otherwise, I guess you'll have to wait to see if Timo can help...
--
Best regards,
Charles
On Thu, 2008-05-22 at 10:14 +0400, Mike Grozak wrote:
dovecot.log:deliver(spam@domain.com): May 16 04:18:48 Info: msgid=01c8b6da$a8bacf80$b7af2abe@sale: save failed to INBOX: Timeout while waiting for lock
You can't really do much about these on Dovecot's side, but you could try reducing the max. number of simultaneous deliver processes your MTA launches.
Another possibility is to upgrade to Dovecot v1.1. There deliver doesn't wait for dovecot-uidlist lock.
participants (3)
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Charles Marcus
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Mike Grozak
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Timo Sirainen