[PROTON-1592] [proton-python] accessing properties of event.receiver in on_link_opened throws exception

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Component/s: python-binding
• Labels: regression
• Assignee: Alan Conway
• Reporter: Jiri Daněk
• Created: 19/Sep/17 09:22
• Updated: 02/Oct/19 17:34
• Resolved: 28/Mar/18 16:55

Description

Apply the following patch to the tx-recv.py example

diff --git a/examples/python/tx_recv.py b/examples/python/tx_recv.py
index 4baddcf5..54f3b489 100755
--- a/examples/python/tx_recv.py
+++ b/examples/python/tx_recv.py
@@ -40,6 +40,9 @@ class TxRecv(MessagingHandler, TransactionHandler):
         self.container.declare_transaction(self.conn, handler=self)
         self.transaction = None
 
+ def on_link_opened(self, event):
+     event.receiver.drain_mode = True
+
     def on_message(self, event):
         print(event.message.body)
         self.transaction.accept(event.delivery)

Now run first tx_send.py, then this tx_recv.py. The second command throws exception

$ LD_LIBRARY_PATH=`pwd`/lib64 PYTHONPATH=`pwd`/lib64/proton/bindings/python python ../examples/python/tx_recv.py
Traceback (most recent call last):
  File "../examples/python/tx_recv.py", line 79, in <module>
    Container(TxRecv(opts.address, opts.messages, opts.batch_size)).run()
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/reactor.py", line 148, in run
    while self.process(): pass
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/reactor.py", line 174, in process
    self._check_errors()
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/reactor.py", line 170, in _check_errors
    _compat.raise_(exc, value, tb)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/__init__.py", line 4068, in dispatch
    ev.dispatch(self.handler)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/__init__.py", line 3977, in dispatch
    result = dispatch(handler, type.method, self)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/__init__.py", line 3857, in dispatch
    return handler.on_unhandled(method, *args)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/reactor.py", line 876, in on_unhandled
    event.dispatch(handler)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/__init__.py", line 3980, in dispatch
    self.dispatch(h, type)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/__init__.py", line 3977, in dispatch
    result = dispatch(handler, type.method, self)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/__init__.py", line 3855, in dispatch
    return m(*args)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/handlers.py", line 298, in on_link_remote_open
    self.on_link_opened(event)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/handlers.py", line 313, in on_link_opened
    dispatch(self.delegate, 'on_link_opened', event)
  File "/home/jdanek/Work/repos/qpid-proton/install/lib64/proton/bindings/python/proton/__init__.py", line 3855, in dispatch
    return m(*args)
  File "../examples/python/tx_recv.py", line 44, in on_link_opened
    event.receiver.drain_mode = True
AttributeError: 'NoneType' object has no attribute 'drain_mode'

To see this is a regression, repeat now with python-qpid-proton 0.17.0 from Pypi. With this previous release, there is success.