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From Christian Schneider <>
Subject Re: [HEADS UP] - Adjustments to ExecutorServiceManager on trunk
Date Thu, 18 Aug 2011 12:07:48 GMT
Am 18.08.2011 13:50, schrieb Claus Ibsen:
> On Thu, Aug 18, 2011 at 1:25 PM, Christian Schneider
> <>  wrote:
>> Hi Claus,
>> I just saw that you also changed the ThreadPoolFactory interface to not use
>> the profiles and instead have several methods again. This completely defeats
>> the purpose of having a small factory interface.
>> I will revert that back.
> The ThreadPoolFactory has an API that is fully non Camel specific.
> There is no Camel API at all in that interface.
> It relies purely on well known JDK terms for thread pools and thus
> makes it much easier for 3rd party to implement a custom factory if
> they need.
> All 4 methods are similar to the JDK Executors API and therefore easy
> for people to understand and implement.
> Your API was a Camel thingy with the ThreadPoolProfile (API from
> Camel) and thus people would have to drag Camel API in their custom
> implementations. Likewise when people needed a cached thread pool,
> then the ThreadPoolProfile would not be able to indicate that.
> I would oppose against putting Camel's API into the SPI when its not necessary.

The class ThreadPoolProfile is not much more than a c struct to combine 
the attributes of a thread pool into a class.
The implementor of a camel spi always has a dependency to the camel API 
as the  spi interface is part of the API. So I see no real problem in 
having this in the interface.
Most spi interfaces reference other camel api classes and many of those 
classes are much more problematic. The ThreadPoolProfile is self 
contained so I see absolutely no problem in having it there.
The similarity to the jdk is important for the ExecutorServiceManager as 
very many people use this. The spi factory will only be used very 
seldomly. So I donĀ“t think the similarity is very important.
In fact it rather hurts as the user has to implement more methods.
>> I worked on these changes quite a long time so the fact that you simply
>> changed things back after we discussed on them and agreed on the changes
>> makes me a bit sad. It also causes me a lot of unplanned work now. I agree
>> with you on some of the things you mentioned.
>> Like for example that it makes sense to offer an API on the
>> ExecutorServiceManager that people are familiar with. So I think using the
>> almost same API as in java is a good thing. I also like the fact that the
>> change on the components is now really small after your change and also that
>> there is a completely compatible ExecutorServiceStrategy as a fallback. That
>> really makes sense for all external components.
>> The problem is that with your changes you also rolled back good things I did
>> that I now have to spend a lot of time bringing in again.
> The trunk is not an experimental branch where people can commit big
> refactorings or changes that break backwards compatible.
> Likewise there is nobody in the community that requires a change in
> the ExecutorServiceStrategy API. This is something you
> came up with because you wanted to adjust the API. This is sometimes
> tempting to do, but is very dangerous. The API should be kept
> stable, especially for Camel 2.x that is 2+ years old, and for a
> feature that has been in there for 18+ months.
Your arguments are true and I have no problems with the fact that you 
want the camel 2.x branch to be quite compatible. The problem I had was 
rather with the way you did this. You changed the code and then asked 
for a heads up. For my changes I first offered a patch and we discussed it.
> We have Camel 3.0 where the API can be more open for changes.
The problem with incompatible changes in major versions only is that 
they accumulate and make the major version very fragile and makes the 
development on that version take a very long time. So I think we should 
try to do as much in minor versions as we can and accept some minor 
incompatiblities. Of course it is very diffcult to judge what is minor.


Christian Schneider

Open Source Architect
Talend Application Integration Division

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