dovecot - Nov 2019 - dovecot: auth: Error: DNS lookup for xxx failed: Name does not resolve

I had a working container with dovecot configured as proxy. And all of a 
sudden I am getting these messages 'dovecot: auth: Error: DNS lookup for 
roosit03 failed: Name does not resolve'
Pinging/nslookup these hostnames is ok

Marc> I had a working container with dovecot configured as proxy. And
Marc> all of a sudden I am getting these messages 'dovecot: auth:
Marc> Error: DNS lookup for roosit03 failed: Name does not resolve'
Marc> Pinging/nslookup these hostnames is ok

Does nslookup work inside the container?  Sounds to me like the setup
isn't working properly, but it's hard to know unless you give us more
details.  Can you spin up another container with the same config but
not running dovecot to do a check on DNS resolution?

Does the container's logs give you more details?  How often do you
stop/restart the container?  I would think that Dovecot in a container
isn't really ideal since you need to access the mailstores, and
somehow you get email delivered to the mailstore by
postfix/sendmail/exim or some other tool.

John

I am sure resolving works fine. I tested this in a running mesos 
container, but also in docker run[1]. I need to have the search local 
option in resolve.conf. 

It was actually working, until I started adding the proxy for 
managesieve, but when I reverted, it still does not work. I think the 
building from cache mislead me.

I suspect this is a different problem, that at some point is giving this 
error. Maybe I need some specific config for the dns-client socket. 

PS. This is just a proxy I need temporary. But I am thinking of creating 
a container that directly connects to ceph storage so you do not need 
any local storage. 

[1]
docker run --dns-search='local' -v /dev/log:/dev/log -it dovecot-proxy 
bash

[2]
passdb {
  driver = ldap
  args = /etc/dovecot/dovecot-ldap.conf.ext
  default_fields = proxy=y host=svr1
}

-----Original Message-----
From: John Stoffel [mailto:john at stoffel.org] 
Sent: zaterdag 30 november 2019 20:51
To: Marc Roos
Cc: dovecot
Subject: Re: dovecot: auth: Error: DNS lookup for xxx failed: Name does 
not resolve


Marc> I had a working container with dovecot configured as proxy. And 
Marc> all of a sudden I am getting these messages 'dovecot: auth:
Marc> Error: DNS lookup for roosit03 failed: Name does not resolve'
Marc> Pinging/nslookup these hostnames is ok

Does nslookup work inside the container?  Sounds to me like the setup 
isn't working properly, but it's hard to know unless you give us more 
details.  Can you spin up another container with the same config but not 
running dovecot to do a check on DNS resolution?

Does the container's logs give you more details?  How often do you 
stop/restart the container?  I would think that Dovecot in a container 
isn't really ideal since you need to access the mailstores, and somehow 
you get email delivered to the mailstore by postfix/sendmail/exim or 
some other tool.

John