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From David Jencks <david_jen...@yahoo.com>
Subject Re: [ApacheDS] Configuration of protocols
Date Thu, 11 Oct 2007 05:30:01 GMT
After a lot of discussion on IRC with Alex we think we have an  
approach we like for providing the acceptors to the servers, so i  
coded most of it up and committed it (rev 583683).  Lets see if I can  
describe it:

- the acceptors get to be components, and they each get a reference  
to a thread pool (Executor).
- there's a DatagramAcceptor and a SocketAcceptor, so the server can  
be sure to get the kind it expects.
- these wrap the Mina acceptor classes to
-- install a final filter
-- assure that some parts of the IoAcceptorConfiguration are  
configured correctly (right now, that ThreadModel.MANUAL is set which  
appears to mean we are using an external thread pool)

Each server has 2 (will be one for non-udp protocols such as ldap)  
Acceptor references.  On start it binds stuff at its port to the  
acceptor and on stop it unbinds.  It supplies a (partially  
configured) IoAcceptorConfiguration to the bind method along with the  
actual protocol handler and the address to bind to.

We were thinking of allowing configuration of a non-default  
AcceptorConfiguration through spring which code-wise would be pretty  
easy but would be much easier with xbean-ization of mina.  Alex added  
the xbean tags and pushed snapshots of mina and I added an  
experimental mina-xbean-spring module to apacheds to build the xbean  
fluff.  NOTE THAT this new module uses mina 1.1.4-SNAPSHOT whereas  
everything else uses mina 1.1.2, so to use xbeanized mina components  
we need to adjust the mina version.  We're hoping the mina guys will  
pick this up and move it to the mina project.

Among other side effects the ApacheDS module isn't needed in the  
servers I've worked on (everything except ldap and ldaps AFAICT).

Alex thought that the filters in one of these acceptors ought to be  
configurable by spring but looking into it more I don't quite see  
how.... it looks like we'd need a filter factory rather than a list  
of filters.  We could presumably take a list of filters and add them  
to the factory one by one as we do with the final filter now.  I  
might be missing something here since I haven't looked at the mina  
code at all.

One bit left to do is renaming the XXXConfiguration to XXXServer or  
something more appropriate and checking to see if anything can be  
pruned.

Of course comments are more than welcome...

thanks
david jencks

On Oct 10, 2007, at 1:00 PM, Alex Karasulu wrote:

> Hi David,
>
> On 10/10/07, David Jencks <david_jencks@yahoo.com> wrote:
>
> On Oct 10, 2007, at 11:35 AM, Alex Karasulu wrote:
>
>> Ok I had some sleep and low and behold the ideas came to me :).  I  
>> think I have a clear picture of
>> what we need to do to handle this properly.  Let me describe that  
>> here then try to figure out how
>> that fits with what you have done and described below.
>>
>> First if Emmanuel is right about NTP needing both protocol end  
>> points on the same port for both
>> transport protocols (UDP/TCP) then there is no need to have twice  
>> the configuration. Then
>> something like these combinations would suffice:
>>
>> <ntpServer port=123>
>>    <#directoryService/>
>>    <#udpAcceptor/>
>>    <#tcpAcceptor/>
>> </ntpServer>
>>
>> Configures both UDP and TCP transports on port 123.
>>
>> <ntpServer port=123>
>>    <#directoryService/>
>>    <#tcpAcceptor/>
>> </ntpServer>
>>
>> Configures only TCP on port 123.
>>
>> <ntpServer port=123>
>>    <#directoryService/>
>>    <#udpAcceptor/>
>> </ntpServer>
>>
>> Configures only UDP on port 123.
>>
>> Note that I did not pass in <#apacheDS/> which is not needed since  
>> this service will depend on the
>> core directory service plus the MINA components.  Depending on  
>> which IoAcceptor is set the respective
>> transport protocol is used.  If both are set then both transports  
>> are to be used.
>>
>> So instead of having the NtpServer class just deal with setting up  
>> a single endpoint for one transport
>> protocol it will handle all endpoints for all transport protocols  
>> and no more configuration bean.  The
>> component is wired directly but how it's wired determines what is  
>> enabled.
>
> In order to make this work and still be typesafe we either have to:
>
> I like the idea of making it type safe.  This can be achieved by  
> making getter/setter pairs for specific
> transport types on the XxxServer use more specific interfaces that  
> are already present in MINA:
>
> DatagramAcceptor or
> SocketAcceptor
>
> This would best settle the type safety issue IMO.
>
> - create different classes for the tcp and udp IoAcceptor instances  
> so you can't hook up the wrong one
>
> They already exist as stated above so this option is best I think.   
> WDYT?
>
> or
>
> - wrap the IoAcceptor get the appropriate BaseIoAcceptorConfig from  
> the wrapper.  This would work if all uses of udp use the same  
> acceptor config and all uses of tcp use the same tcp config.  I'm  
> not qualified to guess if this is the case now and in the  
> forseeable future.  In this case the XXXServer class (currently  
> typically XXXConfiguration) could get a list of IoAcceptorwrapper  
> objects instead of just one or two.
>
> Another aspect I don't know about here is exactly how MINA  
> distributes threads between udp and tcp.  My guess is that MINA has  
> a thread pool that it uses for all incoming requests, whether udp  
> or tcp.
>
> Yes this is the case.  We have two pools: one for the logical  
> request handling and one for the protocol
> codec IO handling.  A thread from one pool hands off the req/resp  
> object to the other.
>
> If we want to preserve a single thread pool for all requests this  
> may take some hoop-jumping-through with separate configuration of  
> the tcp and udp IoAcceptors.  On the other hand I've heard rumors  
> that you can get spring to call a method and use the result as the  
> reference value, so we might be able to do something with  that and  
> preserve a single MinaBean.
>
>
> Anyway if someone wants to explain the desired model here or point  
> me to docs that would be great.
>
> I have some ideas but I'm not so confident.  You're right about  
> more experimentation being needed.  Slowly as we
> chug along and get rid of these distracting issues of configuration  
> we'll be able to best move the MINA component
> assembly out of the ApacheDS object.
>> If the other protocols obey the same requirements where both  
>> transport endpoints are needed on the
>> same port then we can follow this same pattern.  We just have to  
>> watch for the special cases if they
>> do exist.
>>
>> Now what impact does this have on OSGi and on configuration in DIT  
>> for the future.  I don't know that
>> yet and it's something to think about.
>>
>> Ok now inline for discussing your changes ...
>>
>> On 10/10/07, David Jencks <david_jencks@yahoo.com > wrote:
>> In rev 583375  I moved all the non-ldap protocol servers into  
>> independent components and provided 2 NTP implementations as a  
>> basis for further discussion.
>>
>> Ok so you broke it out to have a UdpNtpServer and a TcpNtpServer  
>> which are in them selves what you
>> deem one implementation approach I guess right?
>>
>> Then there is this NtpConfiguration which starts both together as  
>> a configuration bean + manager for the
>> other two services?
>>
>> NtpConfiguration illustrates the approach of a single component to  
>> configure both udp and tcp versions of the same protocol.  This  
>> could trivially be enhanced with flags to enable/disable the tcp  
>> or udp choices.  If we decide on this approach I would rename the  
>> class NtpServer.
>>
>> server.xml configuration of this looks like:
>>
>>   <ntpConfiguration ipPort="80123">
>>     <apacheDs>#apacheDS</apacheDs>
>>   </ntpConfiguration>
>>
>> Ok then this would be close to what I was pointing out above but  
>> it uses this ApacheDS reference
>> instead of feeding in the MINA components.  I would like to see  
>> these configuration objects go away
>> all together without even the ServiceConfiguration base class.   
>> Instead an AbstractServer object can
>> be defined and used for server implementations like NtpServer with  
>> the base configuration details in
>> it.
>>
>> This way we don't have a configuration bean + additional code to  
>> start and stop subordinate services.
>> So let me list it out:
>>
>> AbstractServer (or AbstractService )
>>
>>     Replaces ServiceConfiguration as base class for protocol  
>> servers.  This is the common
>>     denominator for all servers running in ApacheDS.  It may need  
>> some properties moved
>>     into some subtypes since the present ServiceConfiguration has  
>> more than the common
>>     denominator.
>
> Is this any different from renaming ServiceConfiguration to  
> AbstractService?  I tried to avoid extra renamings since I thought  
> it would make the actual changes into components harder to see.
>
> Well there might be more to it like removing some properties that  
> are not common across the board but
> yes this is what it looks like is going to happen.  However note  
> that now the semantics are clear that what
> is being wired is the actual component and not just a bean used to  
> hold configuration information.  Subtypes
> of that server/service will now hold the logic and structures to  
> manage the runtime state of the component.
> I think that's the main goal with this whole get rid of  
> configuration beans effort.
>
> SNIP ...
>
> Alex


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