[Dovecot] No failover from director to backend?

[Timo Sirainen]

People already replied and pointed to poolmon. There is no built-in failure handling, because it's not possible to implement it in a way that works well for everyone. Although I think poolmon could also itself use a bit of tweaking. For example if all hosts became very heavily loaded, poolmon would now probably drop all of them immediately if one if its check connections failed.

On 29.10.2012, at 23.05, Patrick Westenberg wrote:

> Hi,
> 
> no one here who is able to reply to my questions?
> 
> Regards
> Patrick
> 
> 
> 
> Patrick Westenberg schrieb:
>> Hi everyone,
>> 
>> short version:
>> Is there no built in failover mechanism for the director service to
>> handle a backend failure?
>> 
>> Long version:
>> I have a frontend server running the director service and two backends.
>> Due to maintenance I had to shut down one of the backends which caused
>> connection errors for the users being directed to this backend.
>> 
>> I was very surprised as I expected the director to redirect these users
>> to the remaining backend.
>> 
>> Am I wrong or is the director not working as expected?
>> 
>> Regards
>> Patrick
>> 
>> 
>> 
>> # 2.1.6: /usr/local/etc/dovecot/dovecot.conf
>> # OS: Linux 2.6.32-5-amd64 x86_64 Debian 6.0.5
>> auth_mechanisms = plain login
>> director_mail_servers = 172.17.1.1 172.17.1.2
>> director_servers = 172.17.1.3 172.17.1.4
>> lmtp_proxy = yes
>> log_path = /var/log/dovecot.log
>> managesieve_notify_capability = mailto
>> managesieve_sieve_capability = fileinto reject envelope
>> encoded-character vacation subaddress comparator-i;ascii-numeric
>> relational regex imap4flags copy include variables body enotify
>> environment mailbox date ihave
>> protocols = imap pop3 lmtp sieve
>> service auth {
>>   unix_listener /var/spool/postfix/private/auth {
>>     group = postfix
>>     mode = 0666
>>     user = postfix
>>   }
>>   unix_listener auth-userdb {
>>     user = dovecot
>>   }
>> }
>> service director {
>>   fifo_listener login/proxy-notify {
>>     mode = 0666
>>   }
>>   inet_listener {
>>     address = 172.17.1.3
>>     port = 9090
>>   }
>>   unix_listener director-userdb {
>>     mode = 0600
>>   }
>>   unix_listener login/director {
>>     mode = 0666
>>   }
>> }
>> service imap-login {
>>   executable = imap-login director
>> }
>> service lmtp {
>>   inet_listener lmtp {
>>     address = 172.17.1.3
>>     port = 24
>>   }
>> }
>> service managesieve-login {
>>   executable = managesieve-login director
>>   inet_listener sieve {
>>     port = 4190
>>   }
>> }
>> service pop3-login {
>>   executable = pop3-login director
>> }
>> ssl_cert = </etc/ssl/certs/imap.xx.crt
>> ssl_key = </etc/ssl/private/imap.xx.key
>> protocol !smtp {
>>   passdb {
>>     args = proxy=y nopassword=y starttls=any-cert
>>     driver = static
>>   }
>> }
>> protocol smtp {
>>   passdb {
>>     args = /usr/local/etc/dovecot/dovecot-sql.conf.ext
>>     driver = sql
>>   }
>>   userdb {
>>     args = /usr/local/etc/dovecot/dovecot-sql.conf.ext
>>     driver = sql
>>   }
>> }
>> protocol lmtp {
>>   auth_socket_path = director-userdb
>> }
>