fix: Run noop loop in scheduler under dispatcherd flag (#1332)

This PR changes the approach to handle the dispatcherd flag in the
scheduler. Instead or returning an error and creating noise for users,
that also need to modify their deployments to not deploy the scheduler
which would be restarting all the time in default deployments, it
applies a less disruptive approach by just warning about it and running
a noop loop.

Signed-off-by: Alex <[email protected]>

Author: Alex-Izquierdo

src/aap_eda/core/exceptions.py

@@ -43,3 +43,7 @@ class DuplicateEnvKeyError(Exception):
 
 class InvalidEnvKeyError(Exception):
     pass
+
+
+class GracefulExit(Exception):
+    pass

src/aap_eda/core/management/commands/scheduler.py

@@ -70,6 +70,8 @@
 https://github.com/rq/rq-scheduler/blob/master/README.rst
 """
 import logging
+import signal
+import time
 import typing
 from datetime import datetime
 
@@ -79,6 +81,7 @@
 from django_rq.management.commands import rqscheduler
 
 from aap_eda.core import tasking
+from aap_eda.core.exceptions import GracefulExit
 from aap_eda.settings import features
 from aap_eda.utils.logging import startup_logging
 
@@ -167,15 +170,27 @@ class Command(rqscheduler.Command):
 
     def handle(self, *args, **options) -> None:
         if features.DISPATCHERD:
-            self.stderr.write(
-                self.style.ERROR(
-                    "This command is not supported when "
-                    f"{settings.DISPATCHERD_FEATURE_FLAG_NAME} is enabled. "
-                    "Please disable the feature flag in your settings "
-                    "or update your deployment.",
-                )
+            self.stdout.write(
+                self.style.WARNING(
+                    f"{settings.DISPATCHERD_FEATURE_FLAG_NAME} flag "
+                    "is enabled. This command is not required in this setup. "
+                    "You may update your deployment configuration to omit "
+                    "this process. \nRunning in background (noop mode)...",
+                ),
             )
-            raise SystemExit(1)
+
+            def handle_exit(signum, frame):
+                raise GracefulExit()
+
+            signal.signal(signal.SIGTERM, handle_exit)
+            signal.signal(signal.SIGINT, handle_exit)
+
+            try:
+                while True:
+                    time.sleep(60)
+            except GracefulExit:
+                self.stdout.write(self.style.NOTICE("Exiting noop mode."))
+                return
 
         # interval can be set through the command line
         # but we want to manage it through settings

tests/unit/commands/test_rq_cmd_wrapper.py

@@ -12,6 +12,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
+import signal
 from unittest import mock
 
 import pytest
@@ -67,13 +68,16 @@ def test_rqscheduler_command_feature_flag_disabled(
 @mock.patch(
     "aap_eda.core.management.commands.scheduler.features.DISPATCHERD", True
 )
-@mock.patch.object(rqscheduler.Command, "handle", return_value=None)
+@mock.patch("time.sleep")
 def test_rqscheduler_command_feature_flag_enabled(
-    mock_rqscheduler_handle,
+    mock_sleep,
     capsys,
 ):
-    with pytest.raises(SystemExit) as exc_info:
-        call_command("scheduler")
-    assert exc_info.value.code == 1
+    def fake_sleep(_):
+        signal.raise_signal(signal.SIGTERM)
+
+    mock_sleep.side_effect = fake_sleep
+    call_command("scheduler")
     captured = capsys.readouterr()
-    assert "This command is not supported" in captured.err
+    assert "This command is not required" in captured.out
+    assert "Exiting noop mode." in captured.out