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| 1 | +from gevent.hub import getcurrent |
| 2 | +import gevent |
| 3 | +import time |
| 4 | +import logging |
| 5 | + |
| 6 | +from gevent.monkey import get_original |
| 7 | + |
| 8 | +# Guarantee that Task threads will always be proper system threads, regardless of Gevent patches |
| 9 | +Event = get_original("threading", "Event") |
| 10 | + |
| 11 | + |
| 12 | +class ClientEvent(object): |
| 13 | + """ |
| 14 | + An event-signaller object with per-client setting and waiting. |
| 15 | +
|
| 16 | + A client can be any Greenlet or native Thread. This can be used, for example, |
| 17 | + to signal to clients that new data is available |
| 18 | + """ |
| 19 | + |
| 20 | + def __init__(self): |
| 21 | + self.events = {} |
| 22 | + |
| 23 | + def wait(self, timeout: int = 5): |
| 24 | + """Wait for the next data frame (invoked from each client's thread).""" |
| 25 | + ident = id(getcurrent()) |
| 26 | + if ident not in self.events: |
| 27 | + # this is a new client |
| 28 | + # add an entry for it in the self.events dict |
| 29 | + # each entry has two elements, a threading.Event() and a timestamp |
| 30 | + self.events[ident] = [Event(), time.time()] |
| 31 | + |
| 32 | + # We have to reimplement event waiting here as we need native thread events to allow gevent context switching |
| 33 | + wait_start = time.time() |
| 34 | + while not self.events[ident][0].is_set(): |
| 35 | + now = time.time() |
| 36 | + if now - wait_start > timeout: |
| 37 | + return False |
| 38 | + gevent.sleep(0) |
| 39 | + return True |
| 40 | + |
| 41 | + def set(self, timeout=5): |
| 42 | + """Signal that a new frame is available.""" |
| 43 | + now = time.time() |
| 44 | + remove = None |
| 45 | + for ident, event in self.events.items(): |
| 46 | + if not event[0].is_set(): |
| 47 | + # if this client's event is not set, then set it |
| 48 | + # also update the last set timestamp to now |
| 49 | + event[0].set() |
| 50 | + event[1] = now |
| 51 | + else: |
| 52 | + # if the client's event is already set, it means the client |
| 53 | + # did not process a previous frame |
| 54 | + # if the event stays set for more than `timeout` seconds, then assume |
| 55 | + # the client is gone and remove it |
| 56 | + if now - event[1] >= timeout: |
| 57 | + remove = ident |
| 58 | + if remove: |
| 59 | + del self.events[remove] |
| 60 | + |
| 61 | + def clear(self): |
| 62 | + """Clear frame event, once processed.""" |
| 63 | + ident = id(getcurrent()) |
| 64 | + if ident not in self.events: |
| 65 | + logging.error(f"Mismatched ident. Current: {ident}, available:") |
| 66 | + logging.error(self.events.keys()) |
| 67 | + return False |
| 68 | + self.events[id(getcurrent())][0].clear() |
| 69 | + return True |
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