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From Robert Hall <rfh...@berkeley.edu>
Subject Re: [users@httpd] JMeter Load Testing of Tomcat through Apache Proxy
Date Wed, 17 Feb 2010 20:26:14 GMT

On Feb 17, 2010, at 12:06 PM, Dan Denton wrote:

> On Mon, Feb 15, 2010 at 12:53 PM, Robert Hall <rfhall@berkeley.edu>  
> wrote:
>> Dan,
>>
>> On Feb 15, 2010, at 10:37 AM, Dan Denton wrote:
>>
>>> Hello all. I’m trying to load test a login page served by tomcat 6,
>>> proxied through apache 2 with mod_proxy. I’m using JMeter 2.3.4 to
>>> conduct the testing. My thread group consists of 500 sessions , and
>>> the sample is a GET of a simple login page.
>>>
>>> JMeter returns errors for a varying percentage of the samples. The
>>> errors returned are generally the following:
>>>
>>> at
>>> org 
>>> .apache 
>>> .jmeter 
>>> .protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java: 
>>> 1037)
>>> at
>>> org 
>>> .apache 
>>> .jmeter 
>>> .protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java: 
>>> 1023)
>>> at
>>> org 
>>> .apache 
>>> .jmeter.threads.JMeterThread.process_sampler(JMeterThread.java:346)
>>> at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:243)
>>> at java.lang.Thread.run(Unknown Source)
>>>
>>> The issues I’m having are twofold. I’m having difficulty determining
>>> if these errors are coming from JMeter or Tomcat, as they’re  
>>> displayed
>>> in the response window of JMeter. The developers think the error is
>>> coming from JMeter given the last few lines of the trace above.
>>
>> The developers are correct.
>>
>>> Given that I'm not a programmer I should probably take their word  
>>> for it,
>>> but why would JMeter show this error as the response?
>>
>> The system you are running JMeter on isn't able to handle the load.
>>
>>> Second, I've tried tweaking my process counts (startservers,  
>>> maxspare,
>>> etc...) with no change in the outcome. I can mitigate the issue by
>>> pointing JMeter directly to tomcat, but I need this product to go
>>> through our apache proxy for SSL.
>>>
>>> Any help on this would be greatly appreciated.
>>
>> There must be some JMeter setting that will work otherwise you  
>> would be
>> unable
>> to access the webapp over SSL from the system that is hosting JMeter.
>>
>> Try reducing everything to a count of 1 in JMeter.
>>
>> If that doesn't work, there is a problem with the SSL config in  
>> JMeter;
>> google "jmeter ssl".
>>
>> Otherwise, try spreading the load our across several JMeter instances
>> installed on separate systems.
>>
>> - Robert
>>
>
> Thanks for the reply Robert. I've set up JMeter 4 slaves, each with at
> least two 2.8 Ghz procs and 2 GB of RAM, and still regardless of
> whether it's 1 node simulating 400 sessions or 4 nodes each simulating
> 100, I still see these errors at 400 sessions or more. Also, when I
> use multiple slaves to execute the test, the percentage of failures
> when simulating 400 sessions is greater and the failures happen
> earlier in the test.
>
> This makes me think that this isn't just an issue with the systems
> running JMeter, but I'm not sure. I've tried tweaking my SSL Session
> Timeout as well, but with no effect. I did this because watching the
> mod_status page on this apache instance, I can see the current session
> count top out at about 330 every time, then subside. My guess was that
> SSL sessions were somehow bottlenecking.
>
> If anyone has any other suggestions, they would be greatly  
> appreciated.
>

Dan, this sounds like an Apache httpd configuration issue.

Check the values for the 'KeepAliveTimeout' and 'KeepAlive'  
directives, http://httpd.apache.org/docs/2.0/mod/core.html#keepalive

I suggest using "KeepAlive  On" and "KeepAliveTimeout 1"; the latter  
is probably defaulted to 15.

- Robert
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