Solaris-x86-10u8 Dovecot-1.2.7
Large mail setup, with quite a few MX servers working well. Generally everything is super.
But every now and then, we get "bouts of bad weather" - which only lasts a short time, and curiously nearly always occur when mail is sent to customer mailing lists. I suspect mostly because of that 1 message has multiple recipients within the same domain. Perhaps.
Delivery setup as:
main.cf: virtual_transport = dovecot dovecot_destination_recipient_limit = 1 dovecot_destination_concurrency_limit=300
master.cf: dovecot unix - n n - 70 pipe flags=DRhu user=dovecot:dovecot argv=/usr/local/libexec/dovecot/deliver -f ${sender} -d ${recipient}
Errors look something like:
example.com
Dec 06 08:46:25 deliver(rbc-005@example.com): Info: msgid=A22A602A940A45A49EA2C4CC53D27655@UQC.local: saved mail to INBOX
Dec 06 08:46:25 deliver(rbc-002@example.com): Info: msgid=A22A602A940A45A49EA2C4CC53D27655@UQC.local: saved mail to INBOX
Dec 06 08:46:28 deliver(rbc-004@example.com): Error: userdb lookup(rbc-004@example.com) failed: Internal failure
Dec 06 08:46:28 deliver(rbc-011@example.com): Error: userdb lookup(rbc-011@example.com) failed: Internal failure
Dec 06 08:46:28 deliver(rbc-013@example.com): Error: userdb lookup(rbc-013@example.com) failed: Internal failure
Dec 06 08:46:28 deliver(rbc-006@example.com): Error: userdb lookup(rbc-006@example.com) failed: Internal failure
Later on, when it retries, everything goes according to plan and delivery is achieved.
Now this is actually due to slapd saying:
Dec 6 08:46:25 vmx15.unix slapd[3958]: [ID 763815 local4.debug] connection_input: conn=72057 deferring operation: too many executing
And since it happens most frequently with mailing-lists, or mails with many recipients, I would guess it is due to a large number of lookups happening in a very short time.
Since dovecot_destination_recipient_limit=1, I believe 'deliver' is only ever called with just one recipient for "-d", and 'deliver' probably-does-not (?) query LDAP for any of the other "To:" addresses in the message body. Is that the case?
Secondary, the dovecot-ldap.conf for dovecot-auth has:
hosts = 127.0.0.1 172.20.12.33 172.20.12.23 172.20.12.113
So even though localhost's slapd was busy at the time, the other three hosts were definitely not. Is LDAP fail-over ... failing... in this case? How many concurrent queries does dovecot-auth perform? Any way to tweak this value?
Admittedly, postfix/dovecot does handle this situation correctly, as 'temporary failure' and mail delivery is merely delayed. But at the same time, it *could* be something with an easy fix as well.
Thoughts?
Lund
-- Jorgen Lundman | lundman@lundman.net Unix Administrator | +81 (0)3 -5456-2687 ext 1017 (work) Shibuya-ku, Tokyo | +81 (0)90-5578-8500 (cell) Japan | +81 (0)3 -3375-1767 (home)