[omniORB] Dynamic destruction of servants when no clientreferences

[Steven King]

Okeefe, Michael K wrote:

>"Duncan has made a game example application that shows how to do the
>child poa 
>creation and registering of the objects. Google for it. "
>
>Here's the link I think you're referring to, it covers factory pattern,
>garbage collection, and more:
>http://www.grisby.org/presentations/py10tut.pdf
>
>
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>omniORB-list at omniorb-support.com
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>  
>
Thanks for you help,

I thought that I would let the list know of the solution we ended up 
using for reference, please comment and critique.

Each client connection made to request a DOM Document causes a new 
Document servant to be created.  This servant is registered on new 
unique POA (using the rootPOA and the POA Manager of the root POA). 
 Each client is also required to implement a Listener interface and pass 
it with the request for the Document.  This listener and the created POA 
is registered onto a Document Clients register.  
Each servant created by operations on the Document are attached to the 
same POA as that Document.

Upon initialisation, a cleaning thread is created which runs every 30 
seconds or so.  The cleaning thread iterates through the list of known 
clients from the DocumentClients register.  For each client that is no 
longer connected to the ORB (by checking a hit() method on the Listener 
interface), I destory() the POA associated with that clients connection. 
 This destroy in turn cleans up all of the servants registered to this 
POA (calls all of their destructors).

This was done because:
1) We wanted to know when a client was finished and not just remove the 
servants without the clients knowledge.  
     Some clients will be connected for very long periods of time - with 
potentially long wait times between requests.
2) Elegantly clean up all of the servants created from within the 
context of DOM Document servant.
3) Fitted in well with our DOM Document caching mechanism (the cache 
needed to be reevaluated every so often)

Please feel free to comment,

Thanks,

Steve
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