Commit f24067f7 authored by Anael Beutot's avatar Anael Beutot Committed by Antoine Millet
Browse files

Added background calculation for tags

parent b06ef671

cloudcontrol/common/client/tags.py

+40 −6
Original line number Diff line number Diff line
@@ -15,7 +15,8 @@ logger = logging.getLogger(__name__) 


class Tag(object):

    """``class`` that abstract tags and act as a simple container."""

    def __init__(self, name, valuable, ttl=-1, refresh=None, parent=None):

    def __init__(self, name, valuable, ttl=-1, refresh=None, parent=None,

                 background=False):

        """

        :param string name: tag name

        :param valuable: something that gives tag value, string or callable
@@ -26,8 +27,10 @@ class Tag(object): 
                * positive integer in seconds



        :param None,int refresh: period used to refresh tag value on the node

        :param object obj: parent object the tag is attached to, it may be

        :param object parent: parent object the tag is attached to, it may be

            needed for the tag callable to process the tag

        :param bool background: calculate the tag value in a background thread

            (migth be usefull to not block the event loop)

        """

        self.name = name

        self.value = None
@@ -35,6 +38,7 @@ class Tag(object): 
        self.ttl = ttl

        self.refresh = refresh

        self.parent = parent if parent is None else weakref.proxy(parent)

        self.background = bool(background)



        if inspect.isfunction(valuable):

            self.is_function = True
@@ -48,7 +52,10 @@ class Tag(object): 
        else:

            self.value = valuable



        #: timer instance

        self.watcher = None

        #: async watcher in case of background is True

        self.async = None



        # special arguments for tag db

        self.db = None
@@ -65,8 +72,34 @@ class Tag(object): 
    def update_value(self):

        """Called when the tag value may change."""

        prev_value = self.value

        if not self.background:

            self.calculate_value()

            if self.value != prev_value:

                self._handle_registration(prev_value)

            return



        # else

        # create a thread that will run the calculate_value method

        def thread_run():

            self.calculate_value()

            self.async.send()



        # keep previous value in watcher's opaque

        self.async.data = prev_value

        self.async.start()



        th = threading.Thread(target=thread_run)

        th.daemon = True

        th.start()



    def async_cb(self, watcher, revents):

        if watcher.data != self.value:

            self._handle_registration(watcher.data)



        watcher.data = None

        watcher.stop()



    def _handle_registration(self, prev_value):

        if self.db is None:

            # when we calculate the tag, the latter could raise an exception

            # and could provoke a deconnection to the libvirt for example,
@@ -74,9 +107,7 @@ class Tag(object): 
            # include the current (in case this happens, just return)

            return



        if prev_value == self.value:

            return

        elif prev_value is None:

        if prev_value is None:

            # we need to register tag again

            if self.sub_id == '__main__':

                logger.debug('Register tag %s', self.name)
@@ -106,6 +137,9 @@ class Tag(object): 
        """

        :param loop: pyev loop

        """

        if self.background:

            self.async = loop.async(self.async_cb)



        if not self.is_function:

            return