pop3 and dsync master-master replication issue causing duplicate delivery (resolved)
Burak Seydioglu
Burak.Seydioglu at servicenow.com
Mon Feb 13 22:44:57 UTC 2017
I had opened a thread a while ago in regards to dsync duplicate delivery issues. Here is an update in case anybody else is suffering from this:
https://dovecot.org/list/dovecot/2016-April/103973.html
We are using an LDAP backend for userdb and passdb lookups and this is causing multiple replication users to be created. Here is the broken setup:
###############################################
userdb
###############################################
hosts = localhost
dn = cn=dovecot,dc...
dnpass = PASSWORD
ldap_version = 3
base = ou=instances,dc...
deref = never
scope = subtree
user_attrs = \
=home=/mail/spool/hash-%0.2M{ldap:uid}/%{ldap:uid}, \
=mail=maildir:/mail/spool/hash-%0.2M{ldap:uid}/%{ldap:maildrop}
user_filter = (&(objectClass=mailUser)(uid=%n))
iterate_attrs = uid=user
iterate_filter = (objectClass=mailUser)
###############################################
passdsb
###############################################
hosts = localhost
dn = cn=dovecot,dc=dc...
dnpass = PASSWORD
ldap_version = 3
base = ou=instances,dc=dc...
deref = never
scope = subtree
pass_attrs = uid=user,userPassword=password, \
=userdb_home=/mail/spool/hash-%0.2M{ldap:uid}/%{ldap:uid}, \
=userdb_mail=maildir:/mail/spool/hash-%0.2M{ldap:uid}/%{ldap:maildrop}
pass_filter = (&(objectClass=mailUser)(uid=%n))
###############################################
If you don't specify a user attribute in the userdb configuration, dovecot uses the destination email address to create the replication user in addition to users based on the definitions from iterate_attr and pass_attr entries. At the end, multiple replication users are created for the same mailbox causing deleted messages to re-appear and get delivered multiple times.
###############################################
username priority fast sync full sync failed
buraktest1 none 02:07:02 02:07:02 -
buraktest1 at buraktest1.domain.com none 02:57:13 02:57:13 -
###############################################
One thing to note here is that the behavior does not manifest itself during the first delivery/retrieval/delete cycle. You need to repeat the cycle again to expose the issue.
The fix is to define and override the "user" attribute in the userdb configuration:
###############################################
userdb
###############################################
hosts = localhost
dn = cn=dovecot,dc...
dnpass = PASSWORD
ldap_version = 3
base = ou=instances,dc...
deref = never
scope = subtree
user_attrs = \
=user=%{ldap:uid}, \
=home=/mail/spool/hash-%0.2M{ldap:uid}/%{ldap:uid}, \
=mail=maildir:/mail/spool/hash-%0.2M{ldap:uid}/%{ldap:maildrop}
user_filter = (&(objectClass=mailUser)(uid=%n))
iterate_attrs = uid=user
iterate_filter = (objectClass=mailUser)
###############################################
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