kytos.core.helpers

Complexity

Total Complexity

11

Size/Duplication

Total Lines	196
Duplicated Lines	0 %

Test Coverage

Coverage

78.85%

Importance

Changes

0

5 Functions

Rating	Name	Duplication	Size	Complexity
A	get_thread_pool_max_workers()	0	3	1
A	get_time()	0	30	3
A	run_on_thread()	0	21	1
B	listen_to()	0	101	5
A	now()	0	11	1

"""Utilities functions used in Kytos."""
import logging
from concurrent.futures import ThreadPoolExecutor
from datetime import datetime, timezone
from threading import Thread

from kytos.core.config import KytosConfig

__all__ = ['listen_to', 'now', 'run_on_thread', 'get_time']

LOG = logging.getLogger(__name__)

# APP_MSG = "[App %s] %s | ID: %02d | R: %02d | P: %02d | F: %s"


def get_thread_pool_max_workers():
    """Get the number of thread pool max workers."""
    return int(KytosConfig().options["daemon"].thread_pool_max_workers)


# pylint: disable=invalid-name
executor = None
if get_thread_pool_max_workers():
    executor = ThreadPoolExecutor(max_workers=get_thread_pool_max_workers())


def listen_to(event, *events):
    """Decorate Event Listener methods.

    This decorator was built to be used on NAPPs methods to define which
    type of event the method will handle. With this, we will be able to
    'schedule' the app/method to receive an event when a new event is
    registered on the controller buffers.
    By using the run_on_thread decorator, we also guarantee that the method
    (handler) will be called from inside a new thread, avoiding this method to
    block its caller.

    The decorator will add an attribute to the method called 'events', that
    will be a list of the events that the method will handle.

    The event that will be listened to is always a string, but it can represent
    a regular expression to match against multiple Event Types. All listened
    events are documented in :doc:`/developer/listened_events` section.

    Example of usage:

    .. code-block:: python3

        class MyAppClass(KytosApp):
            @listen_to('kytos/of_core.messages.in')
            def my_handler_of_message_in(self, event):
                # Do stuff here...

            @listen_to('kytos/of_core.messages.out')
            def my_handler_of_message_out(self, event):
                # Do stuff here...

            @listen_to('kytos/of_core.messages.in.ofpt_hello',
                       'kytos/of_core.messages.out.ofpt_hello')
            def my_handler_of_hello_messages(self, event):
                # Do stuff here...

            @listen_to('kytos/of_core.message.*.hello')
            def my_other_handler_of_hello_messages(self, event):
                # Do stuff here...

            @listen_to('kytos/of_core.message.*.hello')
            def my_handler_of_hello_messages(self, event):
                # Do stuff here...

            @listen_to('kytos/of_core.message.*')
            def my_stats_handler_of_any_message(self, event):
                # Do stuff here...
    """
    def thread_decorator(handler):
        """Decorate the handler method.

        Returns:
            A method with an `events` attribute (list of events to be listened)
            and also decorated to run on a new thread.

        """
        @run_on_thread
        def threaded_handler(*args):
            """Decorate the handler to run from a new thread."""
            handler(*args)

        threaded_handler.events = [event]
        threaded_handler.events.extend(events)
        return threaded_handler

    def thread_pool_decorator(handler):
        """Decorate the handler method.

        Returns:
            A method with an `events` attribute (list of events to be listened)
            and also decorated to run on in the thread pool

        """
        def done_callback(future):
            """Done callback."""
            if not future.exception():
                _ = future.result()
            else:
                exc_str = f"{type(future.exception())}: {future.exception()}"
                args = (
                    getattr(future, "__inner_args")
                    if hasattr(future, "__inner_args")
                    else tuple()
                )
                LOG.error(f"listen_to handler: {handler}, "
                          f"args: {args}, exception: {exc_str}")

        def inner(*args):
            """Decorate the handler to run in the thread pool."""
            future = executor.submit(handler, *args)
            inner_args = args[1:] if len(args) > 1 else args
            setattr(future, "__inner_args", inner_args)
            future.add_done_callback(done_callback)

        inner.events = [event]
        inner.events.extend(events)
        return inner

    if get_thread_pool_max_workers():
        return thread_pool_decorator
    return thread_decorator


def now(tzone=timezone.utc):
    """Return the current datetime (default to UTC).

    Args:
        tzone (datetime.timezone): Specific time zone used in datetime.

    Returns:
        datetime.datetime.now: Date time with specific time zone.

    """
    return datetime.now(tzone)


def run_on_thread(method):
    """Decorate to run the decorated method inside a new thread.

    Args:
        method (function): function used to run as a new thread.

    Returns:
        Decorated method that will run inside a new thread.
        When the decorated method is called, it will not return the created
        thread to the caller.

    """
    def threaded_method(*args):
        """Ensure the handler method runs inside a new thread."""
        thread = Thread(target=method, args=args)

        # Set daemon mode so that we don't have to wait for these threads
        # to finish when exiting Kytos
        thread.daemon = True
        thread.start()
    return threaded_method


def get_time(data=None):
    """Receive a dictionary or a string and return a datatime instance.

    data = {"year": 2006,
            "month": 11,
            "day": 21,
            "hour": 16,
            "minute": 30 ,
            "second": 00}

    or

    data = "21/11/06 16:30:00"

    2018-04-17T17:13:50Z

    Args:
        data (str, dict): python dict or string to be converted to datetime

    Returns:
        datetime: datetime instance.

    """
    if isinstance(data, str):
        date = datetime.strptime(data, "%Y-%m-%dT%H:%M:%S")
    elif isinstance(data, dict):
        date = datetime(**data)
    else:
        return None
    return date.replace(tzinfo=timezone.utc)