Fix gunicorn deployments that fail to start indexing due to multiple …

…application instances being created. (#473)

knowledge_repo/app/app.py

@@ -47,6 +47,7 @@ def __init__(self, repo, db_uri=None, debug=None, config=None, **kwargs):
         # Add unique identifier for this application isinstance
         self.uuid = str(uuid.uuid4())
         if 'KNOWLEDGE_REPO_MASTER_UUID' not in os.environ:
+            logger.info("Set KNOWLEDGE_REPO_MASTER_UUID to '{}'.".format(self.uuid))
             os.environ['KNOWLEDGE_REPO_MASTER_UUID'] = self.uuid
 
         # Preload default configuration

knowledge_repo/app/deploy/common.py

@@ -75,7 +75,11 @@ def builder_func(self):
 
     @property
     def app(self):
-        return self.builder_func()
+        try:
+            self.__app
+        except AttributeError:
+            self.__app = self.builder_func()
+        return self.__app
 
     def write_temp_files(self):
         import tempfile

knowledge_repo/app/deploy/gunicorn.py

@@ -41,10 +41,6 @@ def load_config(self):
             self.cfg.set(key, value)
 
     def load(self):
-        return self.builder_func()
-
-    def run(self):
         if not self.app.check_thread_support():
             raise RuntimeError("Database configuration is not suitable for deployment (not thread-safe).")
-        self.app.start_indexing()
-        return BaseApplication.run(self)
+        return self.app.start_indexing()

knowledge_repo/app/index.py

@@ -28,6 +28,8 @@ def set_up_indexing_timers(app):
             logger.info("Not spawning index-sync timers for non-master application instance: {}".format(app.uuid))
             return
 
+        logger.info("Spawning index-sync timers for master application instance: {}".format(app.uuid))
+
         def index_watchdog(app):
             while True:
                 if not hasattr(app, 'sync_thread') or not app.sync_thread.is_alive():