Add a method for waiting for unpublished events (#42)

Also update the README to reflect this update.

README.rst

@@ -81,6 +81,7 @@ Publishing an event
     ACTIVITY_TRIGGERED = EiffelActivityTriggeredEvent()
     ACTIVITY_TRIGGERED.data.add("name", "Test activity")
     PUBLISHER.send_event(ACTIVITY_TRIGGERED)
+    PUBLISHER.wait_for_unpublished_events()
 
 Deprecation of routing key
 --------------------------

docs/examples.rst

@@ -24,7 +24,6 @@ This code snippet will subscribe to an ActivityStarted in order to publish an Ac
 
 .. code-block:: python
 
-    import time
     from eiffellib.subscribers import RabbitMQSubscriber
     from eiffellib.publishers import RabbitMQPublisher
     from eiffellib.events import (EiffelActivityTriggeredEvent,
@@ -68,7 +67,7 @@ This code snippet will subscribe to an ActivityStarted in order to publish an Ac
     PUBLISHER.send_event(ACTIVITY_STARTED)
 
     # Wait for event to be received by 'callback'.
-    time.sleep(1)
+    PUBLISHER.wait_for_unpublished_events()
 
 Activity
 --------
@@ -80,7 +79,6 @@ An activity is just a callable which will send ActivityTriggered, Started and Fi
 .. code-block:: python
 
     import os
-    import time
     from eiffellib.subscribers import RabbitMQSubscriber
     from eiffellib.publishers import RabbitMQPublisher
     from eiffellib.events import EiffelAnnouncementPublishedEvent
@@ -117,4 +115,4 @@ An activity is just a callable which will send ActivityTriggered, Started and Fi
     PUBLISHER.send_event(ANNOUNCEMENT)
 
     # Wait for event to be received by 'callback'.
-    time.sleep(1)
+    PUBLISHER.wait_for_unpublished_events()

eiffellib/publishers/eiffel_publisher.py

@@ -1,4 +1,4 @@
-# Copyright 2020 Axis Communications AB.
+# Copyright 2020-2022 Axis Communications AB.
 #
 # For a full list of individual contributors, please see the commit history.
 #
@@ -46,6 +46,15 @@ def send(self, msg):
         """
         raise NotImplementedError
 
+    def wait_for_unpublished_events(timeout=60):
+        """Wait for all unpublished events to become published.
+
+        :raises TimeoutError: If the timeout is reached, this will be raised.
+        :param timeout: A timeout, in seconds, to wait before exiting.
+        :type timeout: int
+        """
+        raise NotImplementedError
+
     def close(self):
         """Close down publisher. Override if special actions are required."""
         self.running = False

eiffellib/publishers/rabbitmq_publisher.py

@@ -184,6 +184,27 @@ def _confirm_delivery(self, method_frame):
                     len(self._deliveries), self._acks, self._nacks)
         _LOG.debug(f"[{current_thread().getName()}] '_confirm_delivery' Lock released")
 
+    def wait_for_unpublished_events(self, timeout=60):
+        """Wait for all unpublished events to become published.
+
+        For the RabbitMQ publisher an event becomes published if the
+        broker (not the consumer) responds with an ACK.
+
+        :raises TimeoutError: If the timeout is reached, this will be raised.
+        :param timeout: A timeout, in seconds, to wait before exiting.
+        :type timeout: int
+        """
+        end = time.time() + timeout
+        deliveries = 0
+        while time.time() < end:
+            time.sleep(0.1)
+            deliveries = len(self._deliveries) + len(self._nacked_deliveries)
+            if deliveries == 0:
+                break
+        else:
+            raise TimeoutError("Timeout (%0.2fs) while waiting for events to publish"
+                               " (%d still unpublished)" % (timeout, deliveries))
+
     def send_event(self, event, block=True):
         """Validate and send an eiffel event to the rabbitmq server.