[vdk-plugins] vdk-kerberos-auth: Separate async event loop

The `VdkAioKerberosClient` implementation that we currently have, utilizes async/await constructs
to speed up some operations. The minikerberos authenticator is the only client that uses the aforementioned
async kerberos client. It uses `asyncio.run()` to execute the async operations, which works with the asyncio
main thread. This is fine in general, as long as other components don't use async/await.

If they do, however, we could end up in a situation, where the kerberos plugin closes the asyncio
main event loop, and breaks the other components that rely on the same thread.

To avoid race conditions and other issues with the asyncio thread, this change introduces a separate
event loop for the minikerberos authenticator.

Testing done: Functional test added.

Signed-off-by: Andon Andonov <andonova@vmware.com>

Author: doks5

projects/vdk-plugins/vdk-kerberos-auth/src/vdk/plugin/kerberos/minikerberos_authenticator.py

@@ -75,7 +75,12 @@ def _kinit(self) -> None:
             async def get_tgt():
                 await krb_client.get_TGT()
 
-            asyncio.run(get_tgt())
+            # Create a separate event loop to avoid interfering with users'
+            # data jobs utilizing asyncio, as well.
+            loop = asyncio.new_event_loop()
+            loop.run_until_complete(get_tgt())
+            loop.close()
+
             krb_client.ccache.to_file(self._ccache_file)
             log.info(
                 f"Got Kerberos TGT for {self._kerberos_principal}@{self._kerberos_realm} "

projects/vdk-plugins/vdk-kerberos-auth/tests/jobs/test-job/20_async_test.py

@@ -0,0 +1,17 @@
+# Copyright 2021 VMware, Inc.
+# SPDX-License-Identifier: Apache-2.0
+import asyncio
+import logging
+
+from vdk.api.job_input import IJobInput
+
+log = logging.getLogger(__name__)
+
+
+async def test_method():
+    await asyncio.sleep(1)
+
+
+def run(job_input: IJobInput):
+    log.info("Test Async step")
+    asyncio.run(test_method())