Handle exceptions in runtime service so unittest can catch them (#813)

* handle exceptions in runtime service so unittest can catch them

* lint

* Update multiprocessing.py

Added typing

* Update multiprocessing.py

* Update multiprocessing.py

* add queue per actor

---------

Co-authored-by: PhilippPlank <32519998+PhilippPlank@users.noreply.github.com>

src/lava/magma/runtime/message_infrastructure/multiprocessing.py

@@ -113,11 +113,13 @@ def start(self):
 
     def build_actor(self, target_fn: ty.Callable, builder: ty.Union[
         ty.Dict['AbstractProcess', 'PyProcessBuilder'], ty.Dict[
-            SyncDomain, 'RuntimeServiceBuilder']]) -> ty.Any:
+            SyncDomain, 'RuntimeServiceBuilder']],
+            exception_q: mp.Queue = None) -> ty.Any:
         """Given a target_fn starts a system (os) process"""
         system_process = SystemProcess(target=target_fn,
                                        args=(),
-                                       kwargs={"builder": builder})
+                                       kwargs={"builder": builder,
+                                               "exception_q": exception_q})
         system_process.start()
         self._actors.append(system_process)
         return system_process

src/lava/magma/runtime/runtime.py

@@ -42,6 +42,7 @@
 from lava.magma.core.run_conditions import (AbstractRunCondition,
                                             RunContinuous, RunSteps)
 from lava.magma.compiler.channels.watchdog import WatchdogManagerInterface
+from multiprocessing import Queue
 
 """Defines a Runtime which takes a lava executable and a pluggable message
 passing infrastructure (for instance multiprocessing+shared memory or ray in
@@ -94,13 +95,15 @@ def target_fn(*args, **kwargs):
     """
     try:
         builder = kwargs.pop("builder")
+        exception_q = kwargs.pop('exception_q')
         actor = builder.build()
+        # No exception occured
+        exception_q.put(None)
         actor.start(*args, **kwargs)
     except Exception as e:
-        print("Encountered Fatal Exception: " + str(e))
-        print("Traceback: ")
-        print(traceback.format_exc())
-        raise e
+        e.trace = traceback.format_exc()
+        exception_q.put(e)
+        raise(e)
 
 
 class Runtime:
@@ -134,6 +137,7 @@ def __init__(self,
         self.num_steps: int = 0
 
         self._watchdog_manager = None
+        self.exception_q = []
 
     def __del__(self):
         """On destruction, terminate Runtime automatically to
@@ -160,6 +164,15 @@ def initialize(self, node_cfg_idx: int = 0):
         self._build_processes()
         self._build_runtime_services()
         self._start_ports()
+
+        # Check if any exception was thrown
+        for q in self.exception_q:
+            e = q.get()
+            if e:
+                print(str(e), e.trace)
+                raise(e)
+        del self.exception_q
+
         self.log.debug("Runtime Initialization Complete")
         self._is_initialized = True
 
@@ -293,17 +306,22 @@ def _build_processes(self):
                 if isinstance(proc_builder, PyProcessBuilder):
                     # Assign current Runtime to process
                     proc._runtime = self
+                    exception_q = Queue()
+                    self.exception_q.append(exception_q)
                     self._messaging_infrastructure.build_actor(target_fn,
-                                                               proc_builder)
+                                                               proc_builder,
+                                                               exception_q)
 
     def _build_runtime_services(self):
         """Builds the runtime services"""
         runtime_service_builders = self._executable.runtime_service_builders
         if self._executable.runtime_service_builders:
             for _, rs_builder in runtime_service_builders.items():
+                self.exception_q.append(Queue())
                 self._messaging_infrastructure. \
                     build_actor(target_fn,
-                                rs_builder)
+                                rs_builder,
+                                self.exception_q[-1])
 
     def _get_resp_for_run(self):
         """