Moved Celery CLI commands to 'manage.py celery' submodule + added extensions:

Added a 'celery queue' command, which is supposed to show queued
Celery tasks (but doesn't work quite as I'd expect).

Added a 'celery purge' command, which purges queued Celery tasks.

README.md

@@ -61,4 +61,6 @@ Pillar requires [Celery](http://www.celeryproject.org/) for background task proc
 turn requires a backend and a broker, for which the default Pillar configuration uses Redis and
 RabbitMQ.
 
-You can run the Celery Worker using `manage.py operations worker`.
+You can run the Celery Worker using `manage.py celery worker`.
+
+Find other Celery operations with the `manage.py celery` command.

pillar/cli/__init__.py

@@ -8,6 +8,7 @@ import logging
 from flask_script import Manager
 
 from pillar import current_app
+from pillar.cli.celery import manager_celery
 from pillar.cli.maintenance import manager_maintenance
 from pillar.cli.operations import manager_operations
 from pillar.cli.setup import manager_setup
@@ -15,6 +16,7 @@ from pillar.cli.setup import manager_setup
 log = logging.getLogger(__name__)
 manager = Manager(current_app)
 
+manager.add_command('celery', manager_celery)
 manager.add_command("maintenance", manager_maintenance)
 manager.add_command("setup", manager_setup)
 manager.add_command("operations", manager_operations)

pillar/cli/celery.py

@@ -0,0 +1,60 @@
+import logging
+
+from flask_script import Manager
+from pillar import current_app
+
+log = logging.getLogger(__name__)
+
+manager_celery = Manager(
+    current_app, usage="Celery operations, like starting a worker or showing the queue")
+
+
+@manager_celery.option('args', nargs='*')
+def worker(args):
+    """Runs a Celery worker."""
+
+    import sys
+
+    argv0 = f'{sys.argv[0]} operations worker'
+    argvother = [
+        '-E',
+        '-l', 'INFO',
+        '--concurrency', '1',
+        '--pool', 'solo',  # No preforking, as PyMongo can't handle connect-before-fork.
+                           # We might get rid of this and go for the default Celery worker
+                           # preforking concurrency model, *if* we can somehow reset the
+                           # PyMongo client and reconnect after forking.
+    ] + list(args)
+
+    current_app.celery.worker_main([argv0] + argvother)
+
+
+@manager_celery.command
+def queue():
+    """Shows queued Celery tasks."""
+
+    from pprint import pprint
+
+    # Inspect all nodes.
+    i = current_app.celery.control.inspect()
+
+    print(50 * '=')
+    print('Tasks that have an ETA or are scheduled for later processing:')
+    pprint(i.scheduled())
+
+    print()
+    print('Tasks that are currently active:')
+    pprint(i.active())
+
+    print()
+    print('Tasks that have been claimed by workers:')
+    pprint(i.reserved())
+    print(50 * '=')
+
+
+@manager_celery.command
+def purge():
+    """Deletes queued Celery tasks."""
+
+    log.warning('Purging all pending Celery tasks.')
+    current_app.celery.control.purge()

pillar/cli/operations.py

@@ -159,23 +159,3 @@ def index_users_update_settings():
             'unordered(roles)'
         ]
     })
-
-
-@manager_operations.option('args', nargs='*')
-def worker(args):
-    """Runs a Celery worker."""
-
-    import sys
-
-    argv0 = f'{sys.argv[0]} operations worker'
-    argvother = [
-        '-E',
-        '-l', 'INFO',
-        '--concurrency', '1',
-        '--pool', 'solo',  # No preforking, as PyMongo can't handle connect-before-fork.
-                           # We might get rid of this and go for the default Celery worker
-                           # preforking concurrency model, *if* we can somehow reset the
-                           # PyMongo client and reconnect after forking.
-    ] + list(args)
-
-    current_app.celery.worker_main([argv0] + argvother)