Re: DNS lookup failure for: hostname

[Yasser <yarafatin@xxxxxxxxx>]

The test ran for two hours on 4/21/2015 between 8pm and 10:50pm. 

I got the SAR report generated using ksar tool and didnt find anything wrong with the resource usage. Memory was almost full but not swapping either. A lot of TCP connections which is expected at this load. CPU and IO looks normal. Please find attached ksar report.  

Thanks,

Yasser

On Wed, Apr 22, 2015 at 9:48 PM, Robert Webb <rwebb@xxxxxxxxxxxx> wrote:

That is exactly what I was thinking.

But on to your real problem....

What do the apache server's resources look like when this starts happening? Things like number of connections, tcp port utilization, cpu, I/O, etc...

Makes me wonder if there isn't something being taxed and causing the server's DNS lookups to time out.

On Wed, 22 Apr 2015 21:44:18 -0400
 Yasser <yarafatin@xxxxxxxxx> wrote:

Yes.  The Apache servers may sound redundant with the current setup, but
in the future it will be used for other purposes like proxying to different
virtual ips,  php  hosting etc.
I cannot change the enterprise suite at this point in time.
So are you running through the F5, load balancing to the two Apache
proxies, then load balancing with the apache proxies to your 10 back end
JBOSS servers?


On Wed, 22 Apr 2015 16:21:29 -0400
Yasser <yarafatin@xxxxxxxxx> wrote:

I am in the midst of performance testing a web application and I get these
errors in Apache logs

[Sat Apr 18 03:01:01 2015] [error] [client xx.xx.xxx.253] proxy: DNS lookup
failure for: jboss-host-name returned by /some/url, referer:
http://f5hostname/context/URI

It occurs only at high load levels. I have seen posts where this error
occurs due to incorrect proxy configuration, but my case doesn't fall under
that I guess. At the very end of the test I get another error - "All
workers are in error state". I think the first DNS error causes all workers
to shutdown.

Can someone point where I could start looking? Please let me know if you
need more details than whats mentioned below.

*More details:*

Apache version: 2.2

mod_cluster: 1.2.4.Final

I have an F5 in front of two Apache servers. There are ten JBoss servers in
the balancer.

Apache configuration snippet: (I am not using proxypass directive, just
modcluster)

<IfModule mod_proxy.c>
   ProxyRequests Off
   ProxyVia On</IfModule>
<IfModule mpm_worker_module>
   ServerLimit, StartServers and worker related attributes configured
here</IfModule>
ProxyPreserveHost OnMemManagerFile /var/cache/httpd
<VirtualHost *:1280>
   ManagerBalancerName some2 (this is the same usedin jboss using
proxylist)
   ........

Logs:

[Tue Apr 21 22:06:25 2015] [debug] mod_proxy_http.c(1973): proxy: HTTP:
serving URL http://jbosshost:8080/uri

[Tue Apr 21 22:06:25 2015] [debug] proxy_util.c(2011): proxy: HTTP: has
acquired connection for (jbosshost)

[Tue Apr 21 22:06:25 2015] [debug] proxy_util.c(2067): proxy: connecting
http://jbosshost:8080/uri

[Tue Apr 21 22:06:25 2015] [error] [client 10.xxx.xxx.xxx] proxy: DNS
lookup failure for: jbosshost returned by /URI

[Tue Apr 21 22:06:25 2015] [debug] proxy_util.c(2029): proxy: HTTP: has
released connection for (jbosshost)

OS:

RHEL 6.5

Attachment: ksar-report.pdf
Description: Adobe PDF document

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