main loop: plugins for periodic functions

cylc/flow/main_loop/__init__.py

@@ -98,6 +98,9 @@ async def my_startup_coroutine(schd, state):
 
    # plugins must be properly installed, in-place PYTHONPATH meddling will
    # not work.
+
+   from setuptools import setup
+
    setup(
        name='my-plugin',
        version='1.0',
@@ -109,18 +112,14 @@ async def my_startup_coroutine(schd, state):
             'my_plugin=my_plugin.my_plugin'
           ]
        }
+   )
 
 Examples
 ^^^^^^^^
 
 For examples see the built-in plugins in the :py:mod:`cylc.flow.main_loop`
 module which are registered in the Cylc Flow ``setup.cfg`` file.
 
-Registration
-^^^^^^^^^^^^
-
-Plugins must be registered using the `cylc.main_loop` entry point.
-
 Coroutines
 ^^^^^^^^^^
 
@@ -152,12 +151,12 @@ async def my_startup_coroutine(schd, state):
 .. autofunction:: cylc.flow.main_loop.periodic
 
 """
-import asyncio
 from collections import deque
 from inspect import (
     getmembers,
     isfunction
 )
+from textwrap import indent
 from time import time
 
 import pkg_resources
@@ -324,7 +323,11 @@ def load(config, additional_plugins=None):
         try:
             module_name = entry_points[plugin_name.replace(' ', '_')]
         except KeyError:
-            raise UserInputError(f'No main-loop plugin: "{plugin_name}"')
+            raise UserInputError(
+                f'No main-loop plugin: "{plugin_name}"\n'
+                + '    Available plugins:\n'
+                + indent('\n'.join(sorted(entry_points)), '        ')
+            )
         # load plugin
         try:
             module = module_name.load()

cylc/flow/main_loop/log_data_store.py

@@ -19,6 +19,9 @@
 
    This plugin is for Cylc developers debugging the data store.
 
+If ``matplotlib`` is installed this plugin will plot results as a PDF in
+the run directory when the suite is shut down (cleanly).
+
 """
 import json
 from pathlib import Path

cylc/flow/main_loop/log_main_loop.py

@@ -19,6 +19,9 @@
 
    This plugin is for Cylc developers debugging main loop operations.
 
+If ``matplotlib`` is installed this plugin will plot results as a PDF in
+the run directory when the suite is shut down (cleanly).
+
 """
 from collections import deque
 import json

cylc/flow/main_loop/log_memory.py

@@ -42,6 +42,9 @@
 
    Set a sensible interval before running suites.
 
+If ``matplotlib`` is installed this plugin will plot results as a PDF in
+the run directory when the suite is shut down (cleanly).
+
 """
 
 import json

cylc/flow/scheduler.py

@@ -43,7 +43,6 @@
 from cylc.flow.daemonize import daemonize
 from cylc.flow.exceptions import (
     CylcError,
-    HostSelectException,
     PointParsingError,
     TaskProxySequenceBoundsError
 )