Avoid deploying misconfigured messaging plugin

Initializes messaging plugin at start which would effectively cancel
deployment of a broken app.

resultsdb/__init__.py

@@ -38,6 +38,7 @@
 from resultsdb.controllers.main import main
 from resultsdb.controllers.api_v2 import api as api_v2
 from resultsdb.controllers.api_v3 import api as api_v3, create_endpoints
+from resultsdb.messaging import load_messaging_plugin
 from resultsdb.models import db
 from . import config
 
@@ -119,6 +120,8 @@ def create_app(config_obj=None):
     else:
         app.logger.info("OpenIDConnect authentication is disabled")
 
+    setup_messaging(app)
+
     app.logger.debug("Finished ResultsDB initialization")
     return app
 
@@ -173,6 +176,21 @@ def setup_logging(app):
         app.logger.addHandler(file_handler)
 
 
+def setup_messaging(app):
+    app.messaging_plugin = None
+    if not app.config["MESSAGE_BUS_PUBLISH"]:
+        app.logger.info("No messaging plugin")
+        return
+
+    plugin_name = app.config["MESSAGE_BUS_PLUGIN"]
+    app.logger.info("Using messaging plugin %s", plugin_name)
+    plugin_args = app.config["MESSAGE_BUS_KWARGS"]
+    app.messaging_plugin = load_messaging_plugin(
+        name=plugin_name,
+        kwargs=plugin_args,
+    )
+
+
 def register_handlers(app):
     # TODO: find out why error handler works for 404 but not for 400
     @app.errorhandler(400)

resultsdb/controllers/common.py

@@ -4,7 +4,6 @@
 
 from resultsdb.models import db
 from resultsdb.messaging import (
-    load_messaging_plugin,
     create_message,
     publish_taskotron_message,
 )
@@ -28,13 +27,10 @@ def commit_result(result):
         result.outcome,
     )
 
-    if app.config["MESSAGE_BUS_PUBLISH"]:
+    if app.messaging_plugin:
         app.logger.debug("Preparing to publish message for result id %d", result.id)
-        plugin = load_messaging_plugin(
-            name=app.config["MESSAGE_BUS_PLUGIN"],
-            kwargs=app.config["MESSAGE_BUS_KWARGS"],
-        )
-        plugin.publish(create_message(result))
+        message = create_message(result)
+        app.messaging_plugin.publish(message)
 
     if app.config["MESSAGE_BUS_PUBLISH_TASKOTRON"]:
         app.logger.debug("Preparing to publish Taskotron message for result id %d", result.id)

resultsdb/messaging.py

@@ -205,7 +205,7 @@ def __init__(self, **kwargs):
         required = ["connection", "destination"]
         for attr in required:
             if getattr(self, attr, None) is None:
-                raise ValueError("%r required for %r." % (attr, self))
+                raise ValueError(f"Missing {attr!r} option for STOMP messaging plugin")
 
     def publish(self, msg):
         msg = json.dumps(msg)

testing/test_app.py

@@ -0,0 +1,49 @@
+from unittest.mock import Mock
+
+from pytest import raises
+
+from resultsdb import setup_messaging
+
+
+def test_app_messaging(app):
+    assert app.messaging_plugin is not None
+    assert type(app.messaging_plugin).__name__ == "DummyPlugin"
+
+
+def test_app_messaging_none():
+    app = Mock()
+    app.config = {"MESSAGE_BUS_PUBLISH": False}
+    setup_messaging(app)
+    app.logger.info.assert_called_once_with("No messaging plugin")
+
+
+def test_app_messaging_stomp():
+    app = Mock()
+    app.config = {
+        "MESSAGE_BUS_PUBLISH": True,
+        "MESSAGE_BUS_PLUGIN": "stomp",
+        "MESSAGE_BUS_KWARGS": {
+            "destination": "results.new",
+            "connection": {
+                "host_and_ports": [("localhost", 1234)],
+            },
+        },
+    }
+    setup_messaging(app)
+    app.logger.info.assert_called_once_with("Using messaging plugin %s", "stomp")
+
+
+def test_app_messaging_stomp_bad():
+    app = Mock()
+    app.config = {
+        "MESSAGE_BUS_PUBLISH": True,
+        "MESSAGE_BUS_PLUGIN": "stomp",
+        "MESSAGE_BUS_KWARGS": {
+            "connection": {
+                "host_and_ports": [("localhost", 1234)],
+            },
+        },
+    }
+    expected_error = "Missing 'destination' option for STOMP messaging plugin"
+    with raises(ValueError, match=expected_error):
+        setup_messaging(app)

testing/test_general.py

@@ -226,6 +226,7 @@ def test_stomp_publish_send_failed(self, mock_stomp):
         assert len(mock_stomp().connect.mock_calls) == 1
         assert len(mock_stomp().disconnect.mock_calls) == 1
 
+
 class TestGetResultsParseArgs:
     # TODO: write something!
     pass