Re: HTTPClient [ Was RE: DNS round robin and JVM DNS lookup caching ]

[sebb <se...@gmail.com>]

On 31/10/2007, Sonam Chauhan <so...@ce.com.au> wrote:
> Thanks Sebb:
>
> I opened this enhancement request for the original DNS caching issue:
>        http://issues.apache.org/bugzilla/show_bug.cgi?id=43730
>

OK, seen it

> > > clients, shouldn't this setting be disobeyed? For instance, suppose
> > > JMeter emulates 10 concurrent clients (10 threads) simultaneously
> > > executing a slow webservice - would 5 connections be made first, and
> the
> > > latter connections be made as the first batch finishes?
> >
> > No idea. Threads could well interact this way.
> >
> > This is one of the reasons that we added the HttpClient sampler, which
> > gives full control over connection re-use.
>
> So does the standard 'HTTP Request' sampler use the built-in Java HTTP
> implementation which is (probably) subject to these limits? If so, I

Yes.

> have a problem :D ... our automated test suite has more than 100 JMX
> testscripts using 'HTTP Request', and not 'HTTP Request HTTPClient'.

Whether you have a problem depends on what you are trying to prove
with the tests, and whether the Java implementation restrictions have
any measurable impact on the tests.

If you suspect a JVM limit is having an effect, try splitting a test
into two or more concurrent separate tests and see if there is a
noticeable difference.

Also you may be able to try changing the Java parameters to suit your tests.

> JMeter Ver 2.1.1. (which we use) application help for 'HTTP Request' and
> 'HTTP Request HTTPClient' states:
>        "There are two versions of the sampler - one uses the default
> Java    HTTP implementation, the other uses Commons HttpClient"
> ... so I didn't know the differences. The 'Samplers' section of the user
> manual does not mention the difference either:
>
> http://jakarta.apache.org/jmeter/usermanual/test_plan.html#samplers
> Is there any more current documentation on HTTPClient?

http://jakarta.apache.org/httpcomponents/httpclient-3.x/

> As these tests don't take the Java limits into account, should I shift
> them to HTTPClient?

See above - are the limits causing a problem?

> The GUI interface for HTTP Request and HTTP Request
> HTTPClient seems identical - so instead of editing all those testcases,
> is it possible to manipulate the JMX XML by doing a search and replace
> en-masse for the sampler name?

Yes, see ConvertHTTPSampler.txt in the extras/ directory.
You'll need to get this from a later version of JMeter or SVN.

However, there have been a lot of improvements to the JMeter
HttpClient code since 2.1.1, and the library itself has been updated,
so I would recommend updating JMeter to 2.3 as well.

> I've also opened enhancement request for the original issue:
>        http://issues.apache.org/bugzilla/show_bug.cgi?id=43730
>
> Kind regards,
> Sonam Chauhan
> --

[snip]

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