Re: DNS lookup failure for: hostname

"Robert Webb" <rwebb@xxxxxxxxxxxx> · Wed, 22 Apr 2015 21:48:35 -0400

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

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