Re: [exim] Strange confusing random slowness

* on the Mon, Jan 22, 2007 at 07:46:03AM -0800, Marc Perkel wrote:

> I have a problem that's confusing me and having a hard time tracking it
> down. One of my exim servers is randomly slow sending email. The symptom
> showed up recently about a week ago around the time I installed 4.66 but
> I don't think it's related.

> Using thunderbird. I'll try to send an email and it will sit there for
> 10 to 20 seconds before it sends. Sometimes it sends instantly. I'm also
> noticing slowness sending to mailman lists.
>
> The server however is hardly loaded at all, and I actually just upgraded
> it to a faster server with more memory but that didn't have any affect
> on the problem.
>
> It acts like it's slow DNS related but tried running my own dedicated
> DNS server that's very fast and it didn't seem to make a difference.
> /etc/resolv is pointing to my DNS server, and I don't think it's DNS but
> it behaves the way things would behave if I had a DNS problem. So that's
> why I'm confused.
>
> Around the same time however I started having random slowness with a
> spamassassin server where processes would back up in memory, but actual
> server load levels would not be high. It is as if these processes are
> waiting on something.
>
> Anyhow - need a clue. Thanks in advance.

I agree. Sounds like DNS resolution to me. Do you have a firewall on the
box? If so, try dropping it, or relaxing your rules. Your dns server
needs to be able to send and receive both tcp and udp packets on port 53.

If that doesn't help, use logwrite at the beginning of each acl to help
determine at what point it's being delayed, or if it's being delayed
before the connect acl.

Mike