Add support for plugin actions

implements blueprint mistral-pluggable-task-actions

Change-Id: If12a0c6835edcabd33027555501dea4f473fc1f5

doc/source/writing_a_plugin_action.rst

@@ -0,0 +1,49 @@
+How to write an Action Plugin
+=============================
+
+1. Write a class based on mistral.actions.base.Actions
+::
+
+ from mistral.actions import base
+
+ class RunnerAction(base.Action):
+    def __init__(self, param):
+        # store the incomming params
+        self.param = param
+
+    def run(self):
+        # return your results here
+        return {'status': 0}
+
+2. Publish the class in a namespace
+   (in your setup.cfg)
+
+::
+
+ [entry_points]
+ myproject.plugins.example =
+    runner = solum.mistral_plugins.somefile:RunnerAction
+
+3. Add the namespace into /etc/mistral/mistral.conf
+   (don't overwrite "mistral.plugins.std")
+
+::
+
+ action_plugins = mistral.plugins.std,myproject.plugins.example
+
+4. Use your plugin
+
+Note on naming the plugin.
+
+ * The namespace is "myproject.plugins.example"
+ * The class is named "runner"
+ * Now you can call the action "example.runner"
+
+::
+
+ Workflow:
+   tasks:
+     myaction:
+       action: example.runner
+       parameters:
+         param: avalue_to_pass_in

etc/mistral.conf.example

@@ -30,6 +30,10 @@ rabbit_password = guest
 # Example: server=api,engine
 #server=all
 
+# List of python module namespaces to search for plug-ins.
+# See: doc/source/writing_a_plugin_action.rst on how to write a plugin.
+action_plugins = mistral.actions.std
+
 [api]
 # Host and port to bind the API server to
 host = 0.0.0.0

mistral/actions/action_factory.py

@@ -15,6 +15,7 @@
 #    limitations under the License.
 
 import inspect
+from oslo.config import cfg
 
 from mistral.actions import base
 from mistral.actions import std_actions
@@ -26,36 +27,29 @@ from mistral.openstack.common import log as logging
 LOG = logging.getLogger(__name__)
 
 _ACTION_CTX_PARAM = 'action_context'
-_STD_NAMESPACE = "std"
-
 _NAMESPACES = {}
 
 
-def _find_or_create_namespace(name):
+def _find_or_create_namespace(full_name):
+    name = full_name.split('.')[-1]
     ns = _NAMESPACES.get(name)
 
     if not ns:
-        ns = base.Namespace(name)
+        ns = base.Namespace(full_name)
         _NAMESPACES[name] = ns
 
     return ns
 
 
-def register_action_class(namespace_name, action_name, action_cls):
-    _find_or_create_namespace(namespace_name).add(action_name, action_cls)
-
-
 def get_registered_namespaces():
     return _NAMESPACES.copy()
 
 
-def _register_standard_action_classes():
-    register_action_class(_STD_NAMESPACE, "echo", std_actions.EchoAction)
-    register_action_class(_STD_NAMESPACE, "http", std_actions.HTTPAction)
-    register_action_class(_STD_NAMESPACE,
-                          "mistral_http", std_actions.MistralHTTPAction)
-    register_action_class(_STD_NAMESPACE, "ssh", std_actions.SSHAction)
-    register_action_class(_STD_NAMESPACE, "email", std_actions.SendEmailAction)
+def _register_action_classes():
+    cfg.CONF.import_opt('action_plugins', 'mistral.config')
+    for py_ns in cfg.CONF.action_plugins:
+        ns = _find_or_create_namespace(py_ns)
+        ns.log()
 
 
 def get_action_class(action_full_name):
@@ -160,5 +154,5 @@ def create_action(db_task):
                                   (db_task, e))
 
 
-# Registering standard actions on module load.
-_register_standard_action_classes()
+# Registering actions on module load.
+_register_action_classes()

mistral/actions/base.py

@@ -15,9 +15,9 @@
 #    limitations under the License.
 
 import abc
+from stevedore import extension
 
 from mistral.openstack.common import log as logging
-from mistral import exceptions as exc
 
 LOG = logging.getLogger(__name__)
 
@@ -86,24 +86,26 @@ class Action(object):
 class Namespace(object):
     """Action namespace."""
 
-    def __init__(self, name):
-        self.name = name
-        self.action_classes = {}  # action name -> action class
-
-    def add(self, action_name, action_cls):
-        if action_name in self.action_classes:
-            raise exc.ActionRegistrationException(
-                "Action is already associated with namespace "
-                "[action_cls=%s, namespace=%s" %
-                (action_cls, self))
-
-        self.action_classes[action_name] = action_cls
+    def __init__(self, namespace):
+        self.name = namespace.split('.')[-1]
+        self.mgr = extension.ExtensionManager(
+            namespace=namespace,
+            invoke_on_load=False)
 
     def contains_action_name(self, name):
-        return name in self.action_classes
+        return name in self.mgr.names()
 
     def get_action_class(self, name):
-        return self.action_classes.get(name)
+        # ExtensionManager has no "get"
+        if self.contains_action_name(name):
+            return self.mgr[name].plugin
+        else:
+            return None
 
     def __len__(self):
-        return len(self.action_classes)
+        # ExtensionManager has no len()
+        return len(self.mgr.names())
+
+    def log(self):
+        for ext in self.mgr:
+            LOG.debug('%s:%s' % (self.name, ext.name))

mistral/config.py

@@ -94,6 +94,11 @@ launch_opt = cfg.ListOpt(
          'api, engine, and executor.'
 )
 
+action_plugins_opt = cfg.ListOpt(
+    'action_plugins',
+    default=['mistral.actions.std'],
+    help='List of namespaces to search for plug-ins.')
+
 
 wf_trace_log_name_opt = cfg.StrOpt('workflow_trace_log_name',
                                    default='workflow_trace',
@@ -110,6 +115,7 @@ CONF.register_opts(db_opts, group='database')
 CONF.register_opts(rabbit_opts, group='rabbit')
 CONF.register_opts(executor_opts, group='executor')
 CONF.register_opt(wf_trace_log_name_opt)
+CONF.register_opt(action_plugins_opt)
 
 CONF.register_cli_opt(use_debugger)
 CONF.register_cli_opt(launch_opt)

requirements.txt

@@ -15,4 +15,5 @@ python-keystoneclient>=0.7.0
 networkx>=1.8
 six>=1.6.0
 SQLAlchemy>=0.7.8,<=0.9.99
+stevedore>=0.14
 yaql==0.2.1 # This is not in global requirements

setup.cfg

@@ -30,3 +30,10 @@ mistral.engine.drivers =
 
 mistral.executor.drivers =
     default = mistral.engine.drivers.default.executor:DefaultExecutor
+
+mistral.actions.std =
+    echo = mistral.actions.std_actions:EchoAction
+    http = mistral.actions.std_actions:HTTPAction
+    mistral_http = mistral.actions.std_actions:MistralHTTPAction
+    ssh = mistral.actions.std_actions:SSHAction
+    email = mistral.actions.std_actions:SendEmailAction