Make engine configurable, make debugger show local variables

To make it easy to set Mistral for debugging.
1) Make engine configurable.
2) Enable debugger via command line. Passing --use-debugger will make PyDev or PyCharm show
 local variables in debugging session.

Also, a tiny fix in action_factory.

Change-Id: Id054ae5156649b1f6bbba7131e54bf21d71c659a

README.rst

@@ -22,10 +22,19 @@ To run Mistral API server perform the following command in a shell:
 Note that an example configuration file can be found in etc/mistral.conf.example.
 
 ### Running Mistral Task Executors
-To run Mistral Task Executor instance perform the following command in a shell:
+To run Mistral Task Executor instance perform the following command in a shell::
 
 *tox -evenv -- python mistral/cmd/task_executor.py --config-file path_to_config*
 
 Note that at least one Executor instance should be running so that workflow tasks are processed by Mistral.
 
+### Debugging
+To debug the engine, create etc/mistral.conf with the settings::
+    [engine]
+    engine = mistral.engine.local.engine
+    [pecan]
+    auth_enable = False
 
+and run in pdb, PyDev or PyCharm::
+
+    mistral/cmd/api --config-file etc/mistral.conf --use-debugger

etc/mistral.conf.example

@@ -19,6 +19,10 @@ default_log_levels = mistral=INFO,mistral.cmd.api=INFO,mistral.api=DEBUG,wsme=DE
 host = 0.0.0.0
 port = 8989
 
+[engine]
+# Mistral engine class (string value)
+#engine=mistral.engine.scalable.engine
+
 [pecan]
 auth_enable = True
 

mistral/api/app.py

@@ -19,6 +19,7 @@ import pecan
 from oslo.config import cfg
 
 from mistral import context as ctx
+from mistral.engine import engine
 from mistral.db import api as db_api
 from mistral.services import periodic
 from mistral.api import access_control
@@ -47,6 +48,7 @@ def setup_app(config=None):
     app_conf = dict(config.app)
 
     db_api.setup_db()
+    engine.load_engine()
     ##TODO(akuznetsov) move this to event scheduling to separate process
     periodic.setup()
 

mistral/cmd/api.py

@@ -29,9 +29,12 @@ from mistral.api import app
 from mistral import config
 from mistral.openstack.common import log as logging
 
-
 eventlet.monkey_patch(
-    os=True, select=True, socket=True, thread=True, time=True)
+    os=True,
+    select=True,
+    socket=True,
+    thread=False if '--use-debugger' in sys.argv else True,
+    time=True)
 
 LOG = logging.getLogger('mistral.cmd.api')
 

mistral/config.py

@@ -24,12 +24,16 @@ from keystoneclient.middleware import auth_token
 from mistral.openstack.common import log
 from mistral import version
 
-
 api_opts = [
     cfg.StrOpt('host', default='0.0.0.0', help='Mistral API server host'),
     cfg.IntOpt('port', default=8989, help='Mistral API server port')
 ]
 
+engine_opts = [
+    cfg.StrOpt('engine', default='mistral.engine.scalable.engine',
+               help='Mistral engine class')
+]
+
 pecan_opts = [
     cfg.StrOpt('root', default='mistral.api.controllers.root.RootController',
                help='Pecan root controller'),
@@ -54,14 +58,25 @@ rabbit_opts = [
     cfg.StrOpt('rabbit_password', default='guest', help='RabbitMQ password')
 ]
 
+use_debugger = cfg.BoolOpt(
+    "use-debugger",
+    default=False,
+    help='Enables debugger. Note that using this option changes how the '
+    'eventlet library is used to support async IO. This could result '
+    'in failures that do not occur under normal operation. '
+    'Use at your own risk.'
+)
+
 CONF = cfg.CONF
 
 CONF.register_opts(api_opts, group='api')
+CONF.register_opts(engine_opts, group='engine')
 CONF.register_opts(pecan_opts, group='pecan')
 CONF.register_opts(auth_token.opts, group='keystone')
 CONF.register_opts(db_opts, group='database')
 CONF.register_opts(rabbit_opts, group='rabbit')
 
+CONF.register_cli_opt(use_debugger)
 
 CONF.import_opt('verbose', 'mistral.openstack.common.log')
 CONF.import_opt('debug', 'mistral.openstack.common.log')
@@ -73,7 +88,6 @@ CONF.import_opt('log_date_format', 'mistral.openstack.common.log')
 CONF.import_opt('use_syslog', 'mistral.openstack.common.log')
 CONF.import_opt('syslog_log_facility', 'mistral.openstack.common.log')
 
-
 cfg.set_defaults(log.log_opts,
                  default_log_levels=['sqlalchemy=WARN',
                                      'eventlet.wsgi.server=WARN'])

mistral/engine/actions/action_factory.py

@@ -45,7 +45,7 @@ def _find_action_result_helper(task, action):
     try:
         return task['service_dsl']['actions'][action.name].get('output', {})
     except (KeyError, AttributeError):
-        return None
+        return {}
 
 
 def get_rest_action(task):

mistral/engine/engine.py

@@ -20,15 +20,16 @@ of workflow executions.
 """
 
 from mistral.openstack.common import importutils
+from oslo.config import cfg
+
+_engine = None
 
 
-# TODO(rakhmerov): make it configurable
-module_name = "mistral.engine.scalable.engine"
-try:
+def load_engine():
+    global _engine
+    module_name = cfg.CONF.engine.engine
     module = importutils.import_module(module_name)
-    IMPL = module.get_engine()
-finally:
-    pass
+    _engine = module.get_engine()
 
 
 def start_workflow_execution(workbook_name, task_name, context=None):
@@ -40,7 +41,7 @@ def start_workflow_execution(workbook_name, task_name, context=None):
     :param context: Execution context which defines a workflow input
     :return: Workflow execution.
     """
-    return IMPL.start_workflow_execution(workbook_name, task_name, context)
+    return _engine.start_workflow_execution(workbook_name, task_name, context)
 
 
 def stop_workflow_execution(workbook_name, execution_id):
@@ -50,7 +51,7 @@ def stop_workflow_execution(workbook_name, execution_id):
     :param execution_id: Workflow execution id.
     :return: Workflow execution.
     """
-    return IMPL.stop_workflow_execution(workbook_name, execution_id)
+    return _engine.stop_workflow_execution(workbook_name, execution_id)
 
 
 def convey_task_result(workbook_name, execution_id, task_id, state, result):
@@ -72,8 +73,8 @@ def convey_task_result(workbook_name, execution_id, task_id, state, result):
     :param result: Task result data.
     :return: Task.
     """
-    return IMPL.convey_task_result(workbook_name, execution_id, task_id,
-                                   state, result)
+    return _engine.convey_task_result(workbook_name, execution_id, task_id,
+                                      state, result)
 
 
 def get_workflow_execution_state(workbook_name, execution_id):
@@ -83,7 +84,7 @@ def get_workflow_execution_state(workbook_name, execution_id):
     :param execution_id: Workflow execution id.
     :return: Current workflow state.
     """
-    return IMPL.get_workflow_execution_state(workbook_name, execution_id)
+    return _engine.get_workflow_execution_state(workbook_name, execution_id)
 
 
 def get_task_state(workbook_name, execution_id, task_id):
@@ -94,4 +95,4 @@ def get_task_state(workbook_name, execution_id, task_id):
     :param task_id: Task id.
     :return: Current task state.
     """
-    return IMPL.get_task_state(workbook_name, execution_id, task_id)
+    return _engine.get_task_state(workbook_name, execution_id, task_id)