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Date: Wed, 11 Dec 2013 09:35:09 -0500 (EST)
From: Ken Giusti <kgiusti@redhat.com>
To: proton@qpid.apache.org, users@qpid.apache.org
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Subject: Python wrapper - SASL and SSL class API
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Thread-Topic: Python wrapper - SASL and SSL class API
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Hi all - just wanted to get some opinions on $Subject:

While I was trying to implement a fix for https://issues.apache.org/jira/browse/PROTON-476  I found that the lifecycle model for the python SASL and SSL objects differs for the C engine.  I think the python wrapper's impl is buggy.

In the C engine, these objects are singletons with respect to their associated transport - there can only be one SSL and SASL object associated with a given transport.  This is enforce by the C api - the transport provides factory classes for these objects.

The python wrapper doesn't enforce this.  For both objects, a "public" constructor is supplied (I say "public" because it is exported by the wrapper's __all__ list).  This makes it trivial for an application to construct multiple instances of SASL/SSL objects that reference the same underlying C object.  While this can technically be done safely using reference counting, I think it may lead to unanticipated behavior - not to mention that it differs from the object model provide by the C engine. 

I'd like to fix this by modifying the python wrapper to remove the SSL and SASL objects from the __all__ list, and provide factory methods on the Transport class for creating instances of these objects.

This would result in a change to the public API. 

Let me know what you think,

thanks,

-- 
-K