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From Jean-Baptiste Onofré ...@nanthrax.net>
Subject Re: [Proposal] New subproject rcomp - Reactive components framework
Date Tue, 08 Aug 2017 12:26:46 GMT
Hi

I will do a new review round tomorrow morning.

Thanks
Regards
JB

On Aug 8, 2017, 13:04, at 13:04, Christian Schneider <chris@die-schneider.net> wrote:
>I now adapted the package names as well as the maven coordinates. All 
>files should now also have the apache headers.
>I also made sure the build now works without any running mqtt or kafka 
>server.
>
>I would be happy about a quick review of the current status. If there 
>are no objections then I will go ahead and ask for a git repository.
>
>Christian
>
>On 03.08.2017 08:02, Jean-Baptiste Onofré wrote:
>> Hi Christian,
>>
>> the proposal is interesting, and I see a first potential use in 
>> Decanter for sure.
>>
>> The comment about Camel is fair as it looks very similar at first
>glance.
>>
>> However, the scope is slightly different IMHO.
>>
>> I checked about the legal. The code should be cleanup for donation 
>> (ASF headers, package names, ...). About the dependency license, for 
>> the reactive-streams, it' OK as it uses Creative Commons Zero into
>the 
>> Public Domain. And Reactor is already under Apache license.
>>
>> The DSL is a hot topic. I understand that leveraging Akka or Reactor 
>> is easier, but I'm a bit concern that we could be too much "coupled".
>> Maybe our own simple DSL could help. Thoughts ?
>>
>> Thanks anyway !
>> Regards
>> JB
>>
>> On 07/19/2017 01:02 PM, Christian Schneider wrote:
>>>
>>>       Scope
>>>
>>> I recently experimented with reactive streams and built a small 
>>> component framework on top of this spec.
>>> See https://github.com/cschneider/reactive-components
>>>
>>> The goal is to have a small API that can encapsulate a protocol and 
>>> transport. The code using such a reactive component should not 
>>> directly depend on the specifics of the transport or protocol. 
>>> Another goal is to have reactive features like back pressure. 
>>> Ultimately I am searching for something like Apache Camel Components
>
>>> but with a lot less coupling. In camel the big problem is that 
>>> components depend on camel core which unfortunately is much more
>than 
>>> a component API. So any camel component is coupled quite tightly to 
>>> all of camel core.
>>>
>>>
>>>       Proposal
>>>
>>> I propose to donate my code to Apache and establish this as a Apache
>
>>> Karaf sub project. Some people like Jean-Baptiste and Hadrian have 
>>> already expressed that they support this and I hope for some more 
>>> feedback and help.
>>>
>>> I chose the Karaf project at the moment but am also open to placing 
>>> this in another Apache project. Some matching projects would be 
>>> Apache Camel, Aries or Felix.
>>>
>>>
>>>       Component API
>>>
>>> I was trying to find the simplest API that would allow similar 
>>> components to camel in one way mode.
>>>
>>> public interface RComponent {
>>>      <T> Publisher<T> from(String destination, Class<T> type);
>>>      <T> Subscriber<T> to(String destination, Class<T> type);
>>> }
>>>
>>> A component is a factory for Publishers and Subscribers. From and to
>
>>> have similar meaning as in camel. The component can be given a
>source 
>>> / target type to produce / consume. So with the OSGi Converter spec 
>>> this would allow to have type safe messaging without coding the 
>>> conversion in every component. Each component is exposed as a
>service 
>>> which encapsulates most of the configuration. All endpoint specific 
>>> configuration can be done using the destination String.
>>>
>>> Publisher and Subscriber are interfaces from the reactive streams
>api 
>>> (http://www.reactive-streams.org/). So they are well defined and
>have 
>>> zero additional dependencies.
>>>
>>> I also considered to use OSGi push streams which is an OSGi spec and
>
>>> would also be an interesting foundation. I decided against that 
>>> though as push streams have no API that is separate from the DSL and
>
>>> will probably not be used a lot outside of OSGi.
>>>
>>> See the examples for how to use this in practice. 
>>> https://github.com/cschneider/reactive-components
>>>
>>>
>>>       Possible use cases
>>>
>>> Two big use cases are reactive microservices that need messaging as 
>>> well as plain camel like integrations.
>>> Another case are the Apache Karaf decanter collectors and appenders.
>
>>> Currently they use a decanter specific API but they could easily be 
>>> converted into the more general rcomp api.
>>> We could also create a bridge to camel components to leverage the 
>>> many existing camel components using the rcomp API as well as 
>>> offering rcomp components to camel.
>>>
>>> Components alone are of course not enough. One big strength of
>Apache 
>>> Camel is the DSL. In case of rcomp I propose to not create our own 
>>> DSL and instead use existing DSLs that work well in OSGi. Two
>examples:
>>>
>>> Akka and reactive streams
>>>
>https://de.slideshare.net/ktoso/reactive-integrations-with-akka-streams
>>>
>>> Reactor and reactive streams
>>>
>https://de.slideshare.net/StphaneMaldini/reactor-30-a-reactive-foundation-for-java-8-and-spring
>
>>>
>>>
>>> Another integration is with REST. It is already possible to
>integrate 
>>> CXF Rest services with reactive streams using some adapters but we 
>>> could have native integration.
>>>
>>>
>>>       Risks and Opportunities
>>>
>>> The main risk I see is not gathering a critical mass of components
>to 
>>> draw more people.
>>> Another risk is that the RComponent API or the reactor streams have 
>>> some unexpected limitations.
>>> The big opportunity I see is that the rcomp API is very simple so
>the 
>>> barrier of entry is low.
>>> I also hope that this might become a new foundation for a simpler
>and 
>>> more modern Apache Camel.
>>>
>>> So this all depends on getting some support by you all.
>>>
>>> Christian
>>>
>>>
>>
>
>-- 
>Christian Schneider
>http://www.liquid-reality.de
>
>Open Source Architect
>http://www.talend.com

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