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From Steven Dolg <>
Subject Re: [C3] Concurrency issues with ComponentProvider
Date Fri, 16 Mar 2012 10:07:05 GMT
Hello again,

using the test project from Thorsten [1] I created a very simple client, 
running several threads to send requests for a randomly selected static 
resource (one of the image files).
(Of course I reverted the "synchronized" in SpringComponentProvider 
before running the tests!)

I ran several scenarios, the biggest one was 1,000,000 requests with 100 
concurrent threads.
After each request, the size of the response was compared to the actual 
size of the requested file.
I ran this several times, both with and without caching, and didn't get 
a single error.

The system handled nearly 1,000 requests per second, so I don't think 
it's not enough load.
I could probably push it a little more, but I doubt this would show a 
different result.

This leads me to believe that there's nothing wrong with handling 
concurrent requests, even under heavy load, when handling static 
resources or other "simple" pipelines.
(Which is also consistent with our Jira, which is not crawling with 
"random strangeness" issues)
Since you *do* have an issue, we should look for other potential sources.

Controllers in general (or your specific one) could be causing problems. 
(The "synchronized" in the SpringComponentProvider could even cause 
parts of the execution before it to be executed sequential instead of 
There's also no controller involved in Thorsten's test project, so this 
would be consistent with what I saw yesterday.

What is your controller doing and could you replace it with some kind of 
static resource to test if that's causing your problem?
Could you try to remove the "synchronized" modifiers one by one and see 
which of them is actually fixing your problem? (I guess it's the one at 
"createComponent", but who knows...).
Could you verify that the HTML page generated by your controller (that's 
how I understood your application) is actually correct when you see a 
wrong result?

The other thing I noticed yesterday, is that the "synchronized" had less 
a performance impact than I expected.
The number of requests handled per second was almost unchanged, probably 
due to the method being synchronized having such a short execution time.
Still I think we should try to avoid this, if at all possible, since we 
are forcing the creating of pipelines to be handled sequentially.



Am 14.03.2012 13:55, schrieb Javier Puerto:
> Hi Cocoon developers,
> we are working in a project based on C3 and we found a strange 
> behaviour when loading the static resources. We are developing a Web 
> 2.0 application and therefore we have a lot of resources (js, images 
> and css). The weird thing is that sometimes the system is returning 
> the wrong resources, returning a js instead of a css or switching 
> images...
> For my tests I did a little modification in class FileReaderComponent 
> to see the source of the file that is being served. See attached file 
> "FileReaderComponent.diff".
> This modification uses System.out to show the source of the file 
> before and after read it. The component seems to be fine, also it's 
> very simple so it seems to not be the cause. The patch allow me to 
> discard the component as cause of problem, the source passed as 
> argument when there's too much resources requests are wrong sometimes.
> I've review how the components are instantiated and I saw a possible 
> design problem for ComponentProvider class.
> <bean name="org.apache.cocoon.sitemap.ComponentProvider" 
> class="org.apache.cocoon.sitemap.SpringComponentProvider">
> <property name="actionFactory" 
> ref="org.apache.cocoon.sitemap.spring.ActionFactory" />
> <property name="languageInterpreterFactory" 
> ref="org.apache.cocoon.sitemap.expression.LanguageInterpreterFactory" />
> <property name="pipelineComponentFactory" 
> ref="org.apache.cocoon.sitemap.spring.PipelineComponentFactory" />
> <property name="pipelineFactory" 
> ref="org.apache.cocoon.sitemap.spring.PipelineFactory" />
> </bean>
> <bean name="org.apache.cocoon.sitemap.Invocation" 
> class="org.apache.cocoon.sitemap.InvocationImpl" scope="prototype">
> <property name="componentProvider" 
> ref="org.apache.cocoon.sitemap.ComponentProvider" />
> </bean>
> Above is the sitemap component configuration, the InvocationImpl is 
> the component that will create the different components thought the 
> ComponentProvider that will delegate on different factories. The 
> problem I see is that while the Invocation is declared as "prototype", 
> the ComponentProvider is a shared instance so it could be that on high 
> demand the methods overlaps between request. I've solved the problem 
> declaring the methods as "synchronized" (att. 
> SpringComponentProvider.diff).
> This will solve the problems with concurrency, but I wonder if it's 
> the best solution. WDYT?
> It's very hard to reproduce the problem with tools like JMeter (better 
> reloading directly in browser). Anyways it's happend sometimes with my 
> current functional test plan but I can't reproduce it consistently. 
> Also the JMeter test plan is designed for our current web project so I 
> can't attach it. The functional tests is configure as:
> * 30 threads
> * No delay between request
> * Ramp up 1s
> * Infinite loop
> * Random controller with 6 static requests, each request with size 
> assertion.
> Please, tell me if you need more detailed tests or it's enough. IMO 
> anybody could see the problem if there's a lot of concurrent resources 
> involved.
> Salu2

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