Implement a timer to increase frequency at special times

punkow/service/timer.py

@@ -0,0 +1,91 @@
+import asyncio
+import contextlib
+import datetime
+import logging
+import typing
+
+import croniter
+import pytz
+
+logger = logging.getLogger(__name__)
+
+
+class TimeStream(object):
+    def __init__(self, timespec, now):
+        self._spec = timespec
+        self._iter = croniter.croniter(timespec, now)
+        self._special_window = datetime.timedelta(minutes=10)
+
+        self._prev = self._iter.get_prev(datetime.datetime)
+        self._next = self._iter.get_next(datetime.datetime)
+
+    def is_between(self, now: datetime.datetime) -> bool:
+
+        while now > self._next:
+            self._prev = self._next
+            self._next = self._iter.get_next(datetime.datetime)
+
+        while now < self._prev:
+            self._next = self._prev
+            self._prev = self._iter.get_prev(datetime.datetime)
+
+        if now - self._special_window < self._prev:
+            logger.debug("Less than 10 minutes since %s -> increase interval", self._prev.isoformat())
+            return True
+
+        if now + self._special_window > self._next:
+            logger.debug("Less than 10 minutes to %s -> increase interval", self._next.isoformat())
+            return True
+
+        return False
+
+
+class Timer(object):
+    def __init__(self, interval: float = 5 * 60,
+                 special_times: typing.List[str] = None,
+                 time_zone: str = 'CET'):
+        self._interval = interval
+        self._special_times = []  # type: typing.List[TimeStream]
+        self._time_zone = pytz.timezone(time_zone)
+
+        now = self._now()
+
+        for line in special_times:
+            if not croniter.croniter.is_valid(line):
+                logger.warning("Special time definition '%s' not valid. Ignoring!")
+            else:
+                self._special_times.append(TimeStream(line, now))
+
+    def _now(self) -> datetime.datetime:
+        utc_now = pytz.utc.localize(datetime.datetime.utcnow())
+        return utc_now.astimezone(self._time_zone)
+
+    def _wait_time(self, now):
+        for special in self._special_times:
+            if special.is_between(now):
+                return 1
+        return self._interval
+
+    @contextlib.asynccontextmanager
+    async def timed(self):
+        start = self._now()
+
+        yield
+
+        end = self._now()
+        elapsed = (end - start).total_seconds()
+        sleep = max(0.0, self._wait_time(end) - elapsed)
+        logger.debug("Booking run completed in %0.2f seconds - now sleep for %0.2f seconds", elapsed, sleep)
+        await asyncio.sleep(sleep)
+
+
+if __name__ == '__main__':
+    t = Timer(20, ["0 0 * * *"])
+    z = pytz.timezone("CET")
+    d = datetime.datetime(2019, 1, 17, 0, 0, 0, 0)
+
+    for i in range(40):
+        tm = d + datetime.timedelta(minutes=i-20)
+
+        inte = t._wait_time(z.localize(tm))
+        print(tm.isoformat(), inte)