History for SynchronousCall

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Multiplexed Zope RPC

  Scenario: Synchronous Call

    Assumptions
     
      - Calling thread wants to send a message to the server and
        await its reply, synchronously.
        
      - The server may send asynchronous messages *directed to the
        calling thread*;  these messages must be handled by that thread.
    
    Procedure

      1. Client thread invokes the ZRPC object, passing the method name
         as the first of a set of arbitrary arguments.

      2. ZRPC finds/creates a ThreadMessageHandler corresponding to the
         current thread ID, and delegates the invocation to it.

      3. The handler marshals its threadID and the passed arguments into
         a message, and calls back up to the ZRPC object to put the
         message on the wire.
       
      4. Handler drops into "consumer mode" on its message queue, processing
         "out-of-band" messages while waiting for a response or exception
         message.

      5. Meanwhile, the asyncore loop is pushing inbound messages to the
         ZRPC object, which unpacks the threadID from the message and
         dispatches it to the corresponding handler, in "producer" mode.
      
      6. The "blocked-in-synchronous call" handler finally receives a
         reply:

          * if it is a normal return, the handler unmarshals the value,
            if any, and returns it.

          * otherwise, the handler unmarshals the exception and raises it.