Fix app init in case timescale listenstore is down

SQLALCHEMY_TIMESCALE_URI can be empty if listenstore_up is set to false in consul config.
In such cases, we want to bring up the flask app with whatever parts possible so that
submit listens endpoint keeps working. Currently, this breaks during flask admin init and
leads to app creation errors.

Add timescale uri to sqlalchemy binds only if listenstore is available and only register
playlist admin views under the same condition.

consul_config.py.ctmpl

@@ -80,16 +80,22 @@ MB_DATABASE_URI = ""
 SQLALCHEMY_TIMESCALE_URI = """postgresql://listenbrainz_ts:{{template "KEY" "timescale_lb_password"}}@{{.Address}}:{{.Port}}/listenbrainz_ts"""
 TIMESCALE_ADMIN_URI = """postgresql://postgres:{{template "KEY" "timescale_admin_password"}}@{{.Address}}:{{.Port}}/postgres"""
 TIMESCALE_ADMIN_LB_URI = """postgresql://postgres:{{template "KEY" "timescale_admin_password"}}@{{.Address}}:{{.Port}}/listenbrainz_ts"""
+# for use in playlists admin view
+SQLALCHEMY_BINDS = {
+   'timescale': SQLALCHEMY_TIMESCALE_URI
+}
     {{end}}
     {{else}}
 SQLALCHEMY_TIMESCALE_URI = "SERVICEDOESNOTEXIST_timescale-listenbrainz"
 TIMESCALE_ADMIN_URI = "SERVICEDOESNOTEXIST_timescale-listenbrainz"
 TIMESCALE_ADMIN_LB_URI = "SERVICEDOESNOTEXIST_timescale-listenbrainz"
+SQLALCHEMY_BINDS = {}
     {{end}}
 {{else}}
 SQLALCHEMY_TIMESCALE_URI = ""
 TIMESCALE_ADMIN_URI=""
 TIMESCALE_ADMIN_LB_URI=""
+SQLALCHEMY_BINDS = {}
 {{end}}
 
 
@@ -101,11 +107,6 @@ MBID_MAPPING_DATABASE_URI = "dbname=musicbrainz_json_dump user=musicbrainz host=
 MBID_MAPPING_DATABASE_URI = ""
 {{end}}
 
-# for use in playlists admin view
-SQLALCHEMY_BINDS = {
-   'timescale': SQLALCHEMY_TIMESCALE_URI
-}
-
 {{if service "typesense-listenbrainz-new"}}
 {{with index (service "typesense-listenbrainz-new") 0}}
 TYPESENSE_HOST = "{{.Address}}"

listenbrainz/webserver/__init__.py

@@ -187,24 +187,8 @@ def after_request_callbacks(response):
     return app
 
 
-def create_web_app(debug=None):
-    """ Generate a Flask app for LB with all configurations done, connections established and endpoints added."""
-    app = create_app(debug=debug)
-
-    # Static files
-    import listenbrainz.webserver.static_manager
-    static_manager.read_manifest()
-    app.static_folder = '/static'
-
-    from listenbrainz.webserver.utils import get_global_props
-    app.context_processor(lambda: dict(
-        get_static_path=static_manager.get_static_path,
-        global_props=get_global_props()
-    ))
-
-    _register_blueprints(app)
-
-    # Admin views
+def init_admin(app):
+    """Initialize admin interface."""
     from listenbrainz import model
     model.db.init_app(app)
 
@@ -227,8 +211,32 @@ def create_web_app(debug=None):
     admin.add_view(ExternalServiceAdminView(ExternalServiceModel, model.db.session, endpoint='external_service_model'))
     admin.add_view(ListensImporterAdminView(ListensImporterModel, model.db.session, endpoint='listens_importer_model'))
     admin.add_view(ReportedUserAdminView(ReportedUsersModel, model.db.session, endpoint='reported_users_model'))
-    admin.add_view(PlaylistAdminView(PlaylistModel, model.db.session, endpoint='playlist_model'))
-    admin.add_view(PlaylistRecordingAdminView(PlaylistRecordingModel, model.db.session, endpoint='playlist_recording_model'))
+
+    # can be empty incase timescale listenstore is down
+    if app.config['SQLALCHEMY_TIMESCALE_URI']:
+        # playlist admin views require timescale database, only register if listenstore is available
+        admin.add_view(PlaylistAdminView(PlaylistModel, model.db.session, endpoint='playlist_model'))
+        admin.add_view(PlaylistRecordingAdminView(PlaylistRecordingModel, model.db.session, endpoint='playlist_recording_model'))
+
+
+def create_web_app(debug=None):
+    """ Generate a Flask app for LB with all configurations done, connections established and endpoints added."""
+    app = create_app(debug=debug)
+
+    # Static files
+    import listenbrainz.webserver.static_manager
+    static_manager.read_manifest()
+    app.static_folder = '/static'
+
+    from listenbrainz.webserver.utils import get_global_props
+    app.context_processor(lambda: dict(
+        get_static_path=static_manager.get_static_path,
+        global_props=get_global_props()
+    ))
+
+    _register_blueprints(app)
+
+    init_admin(app)
 
     @app.before_request
     def before_request_gdpr_check():