sendmail 8.13.1 queue mail when load average above 26

zisser · 02-04-2008, 04:38 AM

Hello,

My Customer has a RH4 with sendmail box. Load Average is around 4 to 8 usually with some peaks.
We installed our client software which open about 20 threads in uninterruptible sleep state (we don't want to go too deep here now and this is not the direction we want to go).
In Linux each thread is counted into the Load Average value.
We then Adjusted the confQUEUE_LA and confREFUSE_LA in /etc/mail/sendmail.mc. This works fine up to Load Average of 25.
Above that value mail is just queuing in /var/spool/clientmqueue.

I spent a lot of time on this case and I have two possible ways to look at this:
1. A bug in sendmail
2. Some other params or components that effect or effected by high Load Average.

I would appreciate any idea....

Regards
udi

gilead · 02-04-2008, 09:00 PM

On a box that is basically a dedicated mail server, the recommendation here is to set QueueLA higher than RefuseLA:

Code:

...the other way around will cause your queue to explode when the 
load is high (assuming you reach QueueLA of course), you accept lots 
of new messages but can't get rid of them as the load average hovers 
around RefuseLA - the many messages in the queue drive up disk I/O and 
thereby the load average.

It sounds like you have it the other way around and your queue is just getting larger. It doesn't sound like a sendmail bug, but since your client software is generating a very large load can you test it with the settings the other way around?

zisser · 02-05-2008, 02:30 AM

Thanks for answering.

my queue is not exploding... it is empty.
The mail is hanging in the clientqueue. And we are talking about one or two emails not more. (this is a test box. in the production the clientqueue can explode... but if I run mailq the results are zero!!!)

Now, I know all about the params and how to set them. The issue here is that while the Load Average is above 26 (!) sendmail queue the mail in clientqueue. Less then 26 mail is processed OK and the params do their job.

The high load avg is not the issue as I read other posts on the web that show higher LA and by adjusting these params the problems go away.

In my case even if I set the params to 100 as long as the current LA is above 26 mail will hang in client queue.

Thanks again,
Udi Zisser.

gilead · 02-05-2008, 04:56 PM

The only info I've seen that might help is here in the sendmail book. They say the values can be set separately for the MTA and MSA - have you tried that yet?

Apart from that, the info here recommends using the following command to flush all the mail off the system:

Code:

sendmail -OQueueLA=100 -q 0 -v

zisser · 02-06-2008, 06:37 AM

Never tried this.
Sound very interesting!!!

But... I really don't know how to do that.
How can I set QueueLA separately for the MTA and MSA???

Thank you,
Udi

gilead · 02-06-2008, 02:11 PM

When you compile sendmail from source, there's a step where you change to the cf/cf directory, create a sendmail.mc file and then build the sendmail.cf file. That step also builds submit.cf from a default submit.mc file. If you also modify the submit.mc file and then build the .cf file, it will do both.

zisser · 02-07-2008, 03:07 AM

Thanks for the answer!

Building sendmail is not an option for me on this case. We are talking about a customer server that will accespt only official RH4 builds.

Can I add the same params as in /etc/mail/sendmail.mc to /etc/mail/submit.mc and use m4 to compile the params to .cf ?
define(`confQUEUE_LA', `40')dnl
define(`confREFUSE_LA', `50')dnl

Thanks,
Udi Zisser

gilead · 02-07-2008, 04:28 PM

Yes you can - that's what I meant, but didn't explain well.

zisser · 02-09-2008, 02:40 PM

Thanks alot !!!!
I do think it worked!

I also found this link that explains the data flow:
http://sial.org/howto/sendmail/#s2

Reading this page connected all the dots...

Regards,
Udi Zisser

gilead · 02-09-2008, 02:44 PM

I'm glad you got it working - thanks for posting the link, it's good info