Add loop helpers and simplify deploy example

examples/deploy.py

@@ -2,65 +2,38 @@
 This example:
 
 1. Connects to the current model
-2. Resets it
-3. Deploy a charm and waits until it's idle
-4. Destroys the unit and application
+2. Deploy a charm and waits until it reports itself active
+3. Destroys the unit and application
 
 """
-import asyncio
-import logging
+from juju import loop
+from juju.model import Model
 
-from juju.model import Model, ModelObserver
 
-
-class MyModelObserver(ModelObserver):
-    async def on_unit_add(self, delta, old, new, model):
-        logging.info(
-            'New unit added: %s', new.name)
-
-    async def on_change(self, delta, old, new, model):
-        for unit in model.units.values():
-            unit_status = unit.data['agent-status']['current']
-            logging.info(
-                'Unit %s status: %s', unit.name, unit_status)
-            if unit_status == 'idle':
-                logging.info(
-                    'Destroying unit %s', unit.name)
-                loop.create_task(unit.destroy())
-
-    async def on_unit_remove(self, delta, old, new, model):
-        app_name = old.application
-        app = model.applications[app_name]
-        if not app.units:
-            logging.info(
-                'Destroying application %s', app.name)
-            loop.create_task(app.destroy())
-            await model.block_until(
-                lambda: len(model.applications) == 0
-            )
-            await model.disconnect()
-            model.loop.stop()
-
-
-async def run():
+async def main():
     model = Model()
+    print('Connecting to model')
     await model.connect_current()
 
-    await model.reset(force=True)
-    model.add_observer(MyModelObserver())
+    try:
+        print('Deploying ubuntu')
+        application = await model.deploy(
+            'ubuntu-10',
+            application_name='ubuntu',
+            series='trusty',
+            channel='stable',
+        )
+
+        print('Waiting for active')
+        await model.block_until(
+            lambda: all(unit.workload_status == 'active'
+                        for unit in application.units))
 
-    await model.deploy(
-        'ubuntu-0',
-        application_name='ubuntu',
-        series='trusty',
-        channel='stable',
-    )
+        print('Removing ubuntu')
+        await application.remove()
+    finally:
+        print('Disconnecting from model')
+        await model.disconnect()
 
 
-logging.basicConfig(level=logging.DEBUG)
-ws_logger = logging.getLogger('websockets.protocol')
-ws_logger.setLevel(logging.INFO)
-loop = asyncio.get_event_loop()
-loop.set_debug(False)
-loop.create_task(run())
-loop.run_forever()
+loop.run(main())

juju/loop.py

@@ -0,0 +1,34 @@
+import asyncio
+import signal
+
+
+def run(*steps):
+    """
+    Helper to run one or more async functions synchronously, with graceful
+    handling of SIGINT / Ctrl-C.
+
+    Returns the return value of the last function.
+    """
+    if not steps:
+        return
+
+    task = None
+    run._sigint = False  # function attr to allow setting from closure
+    loop = asyncio.get_event_loop()
+
+    def abort():
+        task.cancel()
+        run._sigint = True
+
+    loop.add_signal_handler(signal.SIGINT, abort)
+    try:
+        for step in steps:
+            task = loop.create_task(step)
+            loop.run_until_complete(asyncio.wait([task], loop=loop))
+            if run._sigint:
+                raise KeyboardInterrupt()
+            if task.exception():
+                raise task.exception()
+        return task.result()
+    finally:
+        loop.remove_signal_handler(signal.SIGINT)

requirements.txt

@@ -1,3 +1,3 @@
 --index-url https://pypi.python.org/simple/
-
+dateutil
 -e .

tests/test_loop.py

@@ -0,0 +1,19 @@
+import unittest
+import juju.loop
+
+
+class TestLoop(unittest.TestCase):
+    def test_run(self):
+        async def _test():
+            return 'success'
+        self.assertEqual(juju.loop.run(_test()), 'success')
+
+    def test_run_interrupt(self):
+        async def _test():
+            juju.loop.run._sigint = True
+        self.assertRaises(KeyboardInterrupt, juju.loop.run, _test())
+
+    def test_run_exception(self):
+        async def _test():
+            raise ValueError()
+        self.assertRaises(ValueError, juju.loop.run, _test())