Fix: ASGI processes did not support lifetime events

ASGI specification https://asgi.readthedocs.io/en/latest/specs/lifespan.html

Fixes #293
Replaces #294

runtimes/aleph-alpine-3.13-python/init1.py

@@ -23,7 +23,7 @@
 from io import StringIO
 from os import system
 from shutil import make_archive
-from typing import Optional, Dict, Any, Tuple, List, NewType, Union, AsyncIterable
+from typing import Optional, Dict, Any, Tuple, List, NewType, Union, AsyncIterable, Literal
 
 import aiohttp
 import msgpack
@@ -164,6 +164,36 @@ def setup_volumes(volumes: List[Volume]):
     system("mount")
 
 
+async def wait_for_lifespan_event_completion(application: ASGIApplication,
+                                             event: Union[Literal['startup', 'shutdown']]):
+    """
+    Send the startup lifespan signal to the ASGI app.
+    Specification: https://asgi.readthedocs.io/en/latest/specs/lifespan.html
+    """
+
+    lifespan_completion = asyncio.Event()
+
+    def receive():
+        return {
+            'type': f'lifespan.{event}',
+        }
+
+    def send(type: str):
+        if type == f'lifespan.{event}.complete':
+            pass
+        else:
+            logger.warning(f"Unexpected response to startup: {type}")
+
+    while not lifespan_completion.is_set():
+        await application(
+            scope={
+                'type': 'lifespan',
+            },
+            receive=receive,
+            send=send,
+        )
+
+
 def setup_code_asgi(
     code: bytes, encoding: Encoding, entrypoint: str
 ) -> ASGIApplication:
@@ -200,6 +230,8 @@ def setup_code_asgi(
         app = locals[entrypoint]
     else:
         raise ValueError(f"Unknown encoding '{encoding}'")
+
+    asyncio.run(wait_for_lifespan_event_completion(application=app, event='startup'))
     return app
 
 
@@ -364,7 +396,10 @@ async def process_instruction(
             logger.debug("Application terminated")
             # application.communicate()
         else:
-            # Close the cached session in aleph_client:
+            assert isinstance(application, ASGIApplication)
+            await wait_for_lifespan_event_completion(application=application, event='shutdown')
+
+            # Close the cached session in aleph_client: TODO: remove this, use SDK
             from aleph_client.asynchronous import get_fallback_session
 
             session: aiohttp.ClientSession = get_fallback_session()