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From "Alan D. Cabrera" <l...@toolazydogs.com>
Subject Re: [MINA 3.0] filter chains
Date Fri, 26 Aug 2011 14:55:43 GMT

On Aug 26, 2011, at 7:47 AM, Emmanuel Lecharny wrote:

> On 8/26/11 4:28 PM, Alan D. Cabrera wrote:
>> On Aug 26, 2011, at 7:12 AM, Julien Vermillard wrote:
>> 
>>> On Fri, Aug 26, 2011 at 4:07 PM, Emmanuel Lecharny<elecharny@gmail.com>
 wrote:
>>>> On 8/26/11 3:44 PM, Alan D. Cabrera wrote:
>>>>> On Aug 26, 2011, at 6:40 AM, Julien Vermillard wrote:
>>>>> 
>>>>>> On Fri, Aug 26, 2011 at 3:24 PM, Alan D. Cabrera<list@toolazydogs.com>
>>>>>>  wrote:
>>>>>>> On Aug 26, 2011, at 4:14 AM, Julien Vermillard wrote:
>>>>>>> 
>>>>>>>> I modified the API to remove IoFilterChain. Now you are supposed
to
>>>>>>>> give a list of filter to the service before starting it :
>>>>>>>> 
>>>>>>>> // create the fitler chain for this service
>>>>>>>> List<IoFilter>   filters = new ArrayList<IoFilter>();
>>>>>>>> filters.add(new LoggingFilter("byte log filter"));
>>>>>>>> filters.add(new MyCodecFilter());
>>>>>>>> filters.add(new LoggingFilter("pojo log filter"));
>>>>>>>> filters.add(newMyProtocolLogicFilter());
>>>>>>>> 
>>>>>>>> acceptor.setFilters(filters);
>>>>>>>> 
>>>>>>>> acceptor.bind(...);
>>>>>>> How do we make chains where two filters feed into one or one
filter
>>>>>>> feeds two filters?  If you look in my sandbox we can accommodate
this via:
>>>>>>> 
>>>>>>> static import a.m.util.Util. linkParentWithChild; // to be written
>>>>>>> 
>>>>>>> IoFilter foo = new FooFilter();
>>>>>>> LinkStateFilter link = new LinkStateFilter();
>>>>>>> IoFilter checksum = new ChecksumFilter();
>>>>>>> IoFilter log = new LogFilter();
>>>>>>> 
>>>>>>> link.addLinkStateListener(foo);
>>>>>>> linkParentWithChild(foo, checksum);
>>>>>>> linkParentWithChild(link, checksum);
>>>>>>> linkParentWithChild(checksum, log);
>>>>>>> 
>>>>>>> acceptor.setFilters(foo);
>>>>>>> 
>>>>>> About the code in the sandbox :
>>>>>> 
>>>>>> http://svn.apache.org/repos/asf/mina/sandbox/adc/ahc/mina3/src/main/java/org/apache/mina/core/IoFilter.java
>>>>>> I see no IoFilter.addLinkStateListener(..) method, am I looking at
the
>>>>>> right place ?
>>>>> Oops, it was meant to just be a sketch.  :)
>>>>> 
>>>>>> About the "filters feed into one or one filter feeds two filters",
do
>>>>>> you have a concrete use case in mind for that ?
>>>>> The above example does, Foo and the link state filter.  I'm sure that
>>>>> we've discussed this before.  Another example is a mux/demux situation.
 How
>>>>> would all of this fit into the grand scheme of things?
>>>> Yeah, it really should be a graph of filters, not a list of filters.
>>>> 
>>> Well if it's just for demuxing I proposed few mails ago this solution
>>> : http://s.apache.org/A9W
>> I think we need to make graphing a 1st class citizen and not buried inside another
filter class.
> 
> I do agree. The proposed solution on http://s.apache.org/A9W is what we currently have,
and it's tedious to manage.
> 
> It would be way better to be able to let the controler call the next filter based on
an evaluation method based on the current state.
> 
> 
> Now, the question is : how do the controller knows which filter to call next ? It must
have the current state, and it must be able to make the connection.
> 
> For instance, let's say that from filter F we can switch to either filter G or filter
H, depending on the state we transit to in F.
> 
> F --(state1)--> G
> or
> F --(state2)--> H
> 
> That means the controller has a map { (F, state1, G), (F, state2, H)} somewhere. State
should be passed to the controller too :
> 
> ...
> controller.nextFilter( newState );
> ...
> 
> Pretty theorical at this point... I'm sorry not to have a lot of time to code this, I
do realize that for you guys implementing ideas it's a PITA...

I was thinking of a simple DAG some, or all, of the nodes can be FSMs.

-> [FSM1] -> [Filter] -> [FSM2] -> [Filter]

Inside the FSM there could be chains, but there would be one chain per state.  The message
would run its course through the chain and then the next state would be set.  Otherwise things
become intractable.


Regards,
Alan


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