In order to make sure that it can be done, I'm attempting to use Proton-c in a multi-threaded server environment.The basic assumptions that I'm making are:

1. The root data structure that threads can operate on is
   pn_connector_t/pn_connection_t.  An application thread cannotuse
   pn_driver_t without taking measures to ensure that it is the only
   one doing so at a time.
2. As long as no two threads are concurrently operating on the same
   instance of pn_connection_t, everything should work properly.

So far, so good.  There is one interesting exception to the above.

It will commonly be the case that a thread processing the reception of a message from an inbound link will need to indicate to a different outbound link that there is now data to be sent (i.e. activate that link for write). It is likely that the outbound link will be associated with a different connection that the thread is not allowed to use because another thread may be processing it concurrently.

This is not difficult to handle, but it requires that my threading layer be able to get the pn_connector_t associated with the link. Proton-c provides the following linkage: pn_link_t => pn_session_t => pn_connection_t. There's no way to get the pn_connector_t though.

So, I think I need one of two possible changes:

1. Provide linkage from pn_connection_t to pn_connector_t (may be
   architecturally undesirable), or
2. Add a void* context field to pn_connector_t.

Thoughts, Feelings, Emotions?

-Ted

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