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From Dan Denton <random.da...@gmail.com>
Subject Re: [users@httpd] JMeter Load Testing of Tomcat through Apache Proxy
Date Wed, 17 Feb 2010 22:29:59 GMT
On Wed, Feb 17, 2010 at 3:19 PM, Robert Hall <rfhall@berkeley.edu> wrote:
>
> On Feb 17, 2010, at 12:50 PM, Dan Denton wrote:
>
>> On Wed, Feb 17, 2010 at 2:26 PM, Robert Hall <rfhall@berkeley.edu> wrote:
>>>
>>> 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
>>>
>> Thanks again Robert. My apache proxy has both directives already set,
>> and KeepAliveTimeout was indeed set to 15. I tried running the 400
>> session test across 4 slaves with KeepAliveTimout set to 1 and 30, and
>> the same result. A failure rate of approximately 20 percent.
>>
>> Are there any other directives you suggest changing?
>>
>> Thanks...
>>
>
> Surprising that KeepAliveTimeout of 1 and 30 produced the same results.
>
> Other directives: (with KeepAliveTimeout of 1)
>
> MaxKeepAliveRequests - defaults to 100, try raising to 500
>
> Separately, set KeepAlive Off.
>
> Have you looked at the httpd error logs?
>
> - Robert
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>

Robert,

With KeepAliveTimout set to 1, and with MaxKeepAliveRequests set to
either 100 or 500, the same results. When using 4 nodes, 100 sessions
a piece, failure rates are between 10 and 30%. With individual nodes
firing off 400 sessions, failure rates are 10% or less.

With KeepAlive off, the same results. The results are somewhat random,
but around the same failure rates.

Nothing in the error logs that seems to point to this issue. Only
occasional messages regarding child processes during the restarts for
the configuration changes.

So far, none of these changes seem to have had an effect. The failure
rates are the same regardless.

Thanks for the help...

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