Thanks Steven

El 14 de marzo de 2012 15:37, Steven Dolg <steven.dolg@indoqa.com> escribió:
Hi Javier,

that's the first time, I've heard of concurrency issues in C3.
That's not to say there cannot be any, just that it's probably a rare case or you're stressing the system more than anyone else has yet.

Strange, we experienced this kind of problems since the beginning. For your information,
we need 34 request to retrieve all the resources for the homepage (devel environment).
 

Some thoughts top off my head:
- providers and factories should be singletons, as they should not have any state (ie. member variables)
- the invocation must be a prototype, as it has a state
- if "synchronized" reliably fixes the problem, then there is a problem with accessing the same, stateful resource from different threads


Yeah, I didn't investigate further but maybe the problem is only for certain factory.
 

I cannot look into this right now, but I'll sure do this evening.
Are you using trunk or a certain build?

We are using trunk.
 

I might be able to reproduce this on my own, but a reduced version (ie a controller and sitemap) for your setup would certainly help.


I could provide an example block but I don't know if I will have time till next weekend. Here is how we declared the static resources in sitemap:

    <map:pipeline id="static-resources" type="noncaching">
<!--       <map:parameter name="cache-expires" value="access plus 1 weeks"/> -->
     
      <!-- images -->
      <map:match pattern="images/**">
        <map:match pattern="**.*">
          <map:read src="resources/{map:1}.{map:2}" />
        </map:match>
      </map:match>
     
      <!-- css and js -->
      <map:match pattern="**.*">
        <map:read src="resources/{map:1}.{map:2}" />
      </map:match>
     
    </map:pipeline>

I can confirm that the HTML page is well-formed (JMeter tests again) and the problem is in Cocoon side (see FileReader patch for my tests). So to reproduce the problem, a page with 30 <img/> tags loading different images should work and refresh sometimes without cache (ctrl+f5 in FF).



Steven

Salu2
 

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