Ansible Action Pluginの探索

備忘録

AnsibleのAction Pluginは実行時にどのように探索されているのか

Action Pluginについてどのようにコールされているのかがわからず開発で見落としたため、下記を残す。

TaskExecutorのクラス内でメソッドを下記の順で呼んでいる。 run ⇒ _run_loop ⇒ _execute ⇒ _get_action_handler ⇒ _get_action_handler_with_module_context

そして_get_action_handler_with_module_contextの内容は下記

def _get_action_handler_with_module_context(self, templar):
        '''
        Returns the correct action plugin to handle the requestion task action and the module context
        '''
        module_collection, separator, module_name = self._task.action.rpartition(".")
        module_prefix = module_name.split('_')[0]
        if module_collection:
            # For network modules, which look for one action plugin per platform, look for the
            # action plugin in the same collection as the module by prefixing the action plugin
            # with the same collection.
            network_action = "{0}.{1}".format(module_collection, module_prefix)
        else:
            network_action = module_prefix

        collections = self._task.collections

        # Check if the module has specified an action handler
        module = self._shared_loader_obj.module_loader.find_plugin_with_context(
            self._task.action, collection_list=collections
        )
        if not module.resolved or not module.action_plugin:
            module = None
        if module is not None:
            handler_name = module.action_plugin
        # let action plugin override module, fallback to 'normal' action plugin otherwise
        elif self._shared_loader_obj.action_loader.has_plugin(self._task.action, collection_list=collections):
            handler_name = self._task.action
        elif all((module_prefix in C.NETWORK_GROUP_MODULES, self._shared_loader_obj.action_loader.has_plugin(network_action, collection_list=collections))):
            handler_name = network_action
            display.vvvv("Using network group action {handler} for {action}".format(handler=handler_name,
                                                                                    action=self._task.action),
                         host=self._play_context.remote_addr)
        else:
            # use ansible.legacy.normal to allow (historic) local action_plugins/ override without collections search
            handler_name = 'ansible.legacy.normal'
            collections = None  # until then, we don't want the task's collection list to be consulted; use the builtin

        # networking/psersistent connections handling
        if any(((self._connection.supports_persistence and C.USE_PERSISTENT_CONNECTIONS), self._connection.force_persistence)):

            # check handler in case we dont need to do all the work to setup persistent connection
            handler_class = self._shared_loader_obj.action_loader.get(handler_name, class_only=True)
            if getattr(handler_class, '_requires_connection', True):
                # for persistent connections, initialize socket path and start connection manager
                self._play_context.timeout = self._connection.get_option('persistent_command_timeout')
                display.vvvv('attempting to start connection', host=self._play_context.remote_addr)
                display.vvvv('using connection plugin %s' % self._connection.transport, host=self._play_context.remote_addr)

                options = self._connection.get_options()
                socket_path = start_connection(self._play_context, options, self._task._uuid)
                display.vvvv('local domain socket path is %s' % socket_path, host=self._play_context.remote_addr)
                setattr(self._connection, '_socket_path', socket_path)
            else:
                # TODO: set self._connection to dummy/noop connection, using local for now
                self._connection = self._get_connection({}, templar, 'local')

        handler = self._shared_loader_obj.action_loader.get(
            handler_name,
            task=self._task,
            connection=self._connection,
            play_context=self._play_context,
            loader=self._loader,
            templar=templar,
            shared_loader_obj=self._shared_loader_obj,
            collection_list=collections
        )

        if not handler:
            raise AnsibleError("the handler '%s' was not found" % handler_name)

        return handler, module

コードからわかること FQCNで指定があれば

network_action = "{0}.{1}".format(module_collection, module_prefix)

でモジュールを呼ぶAction Pluginへのパスが通ることがわかる。そうでない場合はすべてのモジュールを探索することになる（これはFQCN指定をするべきであるというインセンティブにつながるかもしれない） なので開発する際は<collection_name>.<os_name>のAction Pluginが最低限必要であることがわかる。