Upgrade to thespian 3.8.0

With this commit we upgrade to thespian 3.8.0 and replace a workaround
to use multiple timers per actor with the now available proper solution.

Closes #318

esrally/driver/driver.py

@@ -131,7 +131,10 @@ def __init__(self, metrics, next_task_scheduled_in):
 
 
 class DriverActor(actor.RallyActor):
+    RESET_RELATIVE_TIME_MARKER = "reset_relative_time"
+
     WAKEUP_INTERVAL_SECONDS = 1
+
     """
     Coordinates all worker drivers. This is actually only a thin actor wrapper layer around ``Driver`` which does the actual work.
     """
@@ -156,9 +159,7 @@ def receiveMessage(self, msg, sender):
             elif isinstance(msg, UpdateSamples):
                 self.update_samples(msg)
             elif isinstance(msg, thespian.actors.WakeupMessage):
-                # workaround to detect multiple timers firing at different intervals. We should actually determine them via some other means
-                # e.g. a payload.
-                if msg.delayPeriod != datetime.timedelta(seconds=DriverActor.WAKEUP_INTERVAL_SECONDS):
+                if msg.payload == DriverActor.RESET_RELATIVE_TIME_MARKER:
                     self.coordinator.reset_relative_time()
                 elif not self.coordinator.finished():
                     self.coordinator.update_progress_message()
@@ -221,9 +222,7 @@ def complete_current_task(self, driver):
 
     def on_task_finished(self, metrics, next_task_scheduled_in):
         if next_task_scheduled_in > 0:
-            assert next_task_scheduled_in != DriverActor.WAKEUP_INTERVAL_SECONDS, \
-                "Due to a (temporary) workaround the task schedule interval must be different than the wakeup interval."
-            self.wakeupAfter(datetime.timedelta(seconds=next_task_scheduled_in))
+            self.wakeupAfter(datetime.timedelta(seconds=next_task_scheduled_in), payload=DriverActor.RESET_RELATIVE_TIME_MARKER)
         else:
             self.coordinator.reset_relative_time()
         self.send(self.start_sender, TaskFinished(metrics, next_task_scheduled_in))

setup.py

@@ -27,7 +27,7 @@ def str_from_file(name):
     "jsonschema==2.5.1",
     "Jinja2==2.9.5",
     # remote messaging
-    "thespian==3.7.3",
+    "thespian==3.8.0",
     # recommended library for thespian to identify actors more easily with `ps`
     # "setproctitle==1.1.10",
     # always use the latest version, these are certificate files...