evennia/src/scripts/tickerhandler.py

"""
TickerHandler

This implements an efficient Ticker which uses a subscription
model to 'tick' subscribed objects at regular intervals.

The ticker mechanism is used by importing and accessing
the instantiated TICKER_HANDLER instance in this module. This
instance is run by the server; it will save its status across
server reloads and be started automaticall on boot.

Example:

    from src.scripts.tickerhandler import TICKER_HANDLER

    # tick myobj every 15 seconds
    TICKER_HANDLER.add(myobj, 15)

The handler will by default try to call a hook "at_tick()"
on the subscribing object. The hook's name can be changed
if the "hook_key" keyword is given to the add() method (only
one such alternate name per interval though). The
handler will transparently set up and add new timers behind
the scenes to tick at given intervals, using a TickerPool.

To remove:

    TICKER_HANDLER.remove(myobj, 15)

The interval must be given since a single object can be subcribed
to many different tickers at the same time.


The TickerHandler's functionality can be overloaded by modifying the
Ticker class and then changing TickerPool and TickerHandler to use the
custom classes

class MyTicker(Ticker):
    # [doing custom stuff]

class MyTickerPool(TickerPool):
    ticker_class = MyTicker
class MyTickerHandler(TickerHandler):
    ticker_pool_class = MyTickerPool

If one wants to duplicate TICKER_HANDLER's auto-saving feature in
a  custom handler one can make a custom AT_STARTSTOP_MODULE entry to
call the handler's save() and restore() methods when the server reboots.

"""
from twisted.internet.defer import inlineCallbacks
from twisted.internet.task import LoopingCall
from src.server.models import ServerConfig
from src.utils.logger import log_trace
from src.utils.dbserialize import dbserialize, dbunserialize, pack_dbobj, unpack_dbobj

_GA = object.__getattribute__
_SA = object.__setattr__


class Ticker(object):
    """
    Represents a repeatedly running task that calls
    hooks repeatedly. Overload _callback to change the
    way it operates.
    """

    @inlineCallbacks
    def _callback(self):
        """
        This will be called repeatedly every self.interval seconds.
        self.subscriptions contain tuples of (obj, args, kwargs) for
        each subscribing object.

        If overloading, this callback is expected to handle all
        subscriptions when it is triggered. It should not return
        anything and should not traceback on poorly designed hooks.
        The callback should ideally work under @inlineCallbacks so it can yield
        appropriately.
        """
        for key, (obj, args, kwargs) in self.subscriptions.items():
            hook_key = yield kwargs.get("hook_key", "at_tick")
            try:
                yield _GA(obj, hook_key)(*args, **kwargs)
            except Exception:
                log_trace()

    def __init__(self, interval):
        """
        Set up the ticker
        """
        self.interval = interval
        self.subscriptions = {}
        # set up a twisted asynchronous repeat call
        self.task = LoopingCall(self._callback)

    def validate(self):
        """
        Start/stop the task depending on how many
        subscribers we have using it.
        """
        subs = self.subscriptions
        if None in subs.values():
            # clean out objects that may have been deleted
            subs = dict((store_key, obj) for store_key, obj in subs if obj)
            self.subscriptions = subs
        if self.task.running:
            if not subs:
                self.task.stop()
        elif subs:
            self.task.start(self.interval, now=False)

    def add(self, store_key, obj, *args, **kwargs):
        """
        Sign up a subscriber to this ticker
        """
        self.subscriptions[store_key] = (obj, args, kwargs)
        self.validate()

    def remove(self, store_key):
        """
        Unsubscribe object from this ticker
        """
        self.subscriptions.pop(store_key, False)
        self.validate()

    def stop(self):
        """
        Kill the Task, regardless of subscriptions
        """
        self.subscriptions = {}
        self.validate()


class TickerPool(object):
    """
    This maintains a pool of Twisted LoopingCall tasks
    for calling subscribed objects at given times.
    """
    ticker_class = Ticker

    def __init__(self):
        "Initialize the pool"
        self.tickers = {}

    def add(self, store_key, obj, interval, *args, **kwargs):
        """
        Add new ticker subscriber
        """
        if interval not in self.tickers:
            self.tickers[interval] = self.ticker_class(interval)
        self.tickers[interval].add(store_key, obj, *args, **kwargs)

    def remove(self, store_key, interval):
        """
        Remove subscription from pool
        """
        if interval in self.tickers:
            self.tickers[interval].remove(store_key)

    def stop(self, interval=None):
        """
        Stop all scripts in pool. This is done at server reload since
        restoring the pool will automatically re-populate the pool.
        If interval is given, only stop tickers with that interval.
        """
        if interval and interval in self.tickers:
            self.tickers[interval].stop()
        else:
            for ticker in self.tickers.values():
                ticker.stop()


class TickerHandler(object):
    """
    The Tickerhandler maintains a pool of tasks for subscribing
    objects to various tick rates.  The pool maintains creation
    instructions and and re-applies them at a server restart.
    """
    ticker_pool_class = TickerPool

    def __init__(self, save_name="ticker_storage"):
        """
        Initialize handler
        """
        self.ticker_storage = {}
        self.save_name = save_name
        self.ticker_pool = self.ticker_pool_class()

    def _store_key(self, obj, interval):
        """
        Tries to create a store_key for the object.
        Returns a tuple (isdb, store_key) where isdb
        is a boolean True if obj was a database object,
        False otherwise.
        """
        try:
            obj = obj.typeclass
        except AttributeError:
            pass
        dbobj = None
        try:
            dbobj = obj.dbobj
        except AttributeError:
            pass
        isdb = True
        if dbobj:
            # create a store_key using the database representation
            objkey = pack_dbobj(dbobj)
        else:
            # non-db object, look for a property "key" on it, otherwise
            # use its memory location.
            try:
                objkey = _GA(obj, "key")
            except AttributeError:
                objkey = id(obj)
            isdb = False
        # return sidb and store_key
        return isdb, (objkey, interval)

    def save(self):
        """
        Save ticker_storage as a serialized string into a temporary
        ServerConf field. This is called by server when it shuts down
        """
        #print "save:", self.ticker_storage
        if self.ticker_storage:
            ServerConfig.objects.conf(key=self.save_name,
                                    value=dbserialize(self.ticker_storage))
        else:
            ServerConfig.objects.conf(key=self.save_name, delete=True)

    def restore(self):
        """
        Restore ticker_storage from database and re-initialize the handler from storage. This is triggered by the server at restart.
        """
        # load stored command instructions and use them to re-initialize handler
        ticker_storage = ServerConfig.objects.conf(key=self.save_name)
        if ticker_storage:
            self.ticker_storage = dbunserialize(ticker_storage)
            #print "restore:", self.ticker_storage
            for (obj, interval), (args, kwargs) in self.ticker_storage.items():
                obj = unpack_dbobj(obj)
                _, store_key = self._store_key(obj, interval)
                self.ticker_pool.add(store_key, obj, interval, *args, **kwargs)

    def add(self, obj, interval, *args, **kwargs):
        """
        Add object to tickerhandler. The object must have an at_tick
        method. This will be called every interval seconds until the
        object is unsubscribed from the ticker.
        """
        isdb, store_key = self._store_key(obj, interval)
        if isdb:
            self.ticker_storage[store_key] = (args, kwargs)
            self.save()
        self.ticker_pool.add(store_key, obj, interval, *args, **kwargs)

    def remove(self, obj, interval):
        """
        Remove object from ticker with given interval.
        """
        isdb, store_key = self._store_key(obj, interval)
        if isdb:
            self.ticker_storage.pop(store_key, None)
            self.save()
        self.ticker_pool.remove(store_key, interval)

    def clear(self, interval=None):
        """
        Stop/remove all tickers from handler, or the ones
        with a given interval. This is the only supported
        way to kill tickers for non-db objects. If interval
        is given, only stop tickers with this interval.
        """
        self.ticker_pool.stop(interval)
        if interval:
            self.ticker_storage = dict((store_key, store_key) for store_key in self.ticker_storage if store_key[1] != interval)
        else:
            self.ticker_storage = {}
        self.save()

    def all(self, interval=None):
        """
        Get the subsciptions for a given interval. If interval
        is not given, return a dictionary with lists for every
        interval in the tickerhandler.
        """
        if interval is None:
            # return dict of all, ordered by interval
            return dict((interval, ticker.subscriptions.values())
                         for interval, ticker in self.ticker_pool.tickers.items())
        else:
            # get individual interval
            ticker = self.ticker_pool.tickers.get(interval, None)
            if ticker:
                return ticker.subscriptions.values()

# main tickerhandler
TICKER_HANDLER = TickerHandler()