Add experimental reconnection logic.

discord/backoff.py

@@ -0,0 +1,85 @@
+# -*- coding: utf-8 -*-
+
+"""
+The MIT License (MIT)
+
+Copyright (c) 2015-2017 Rapptz
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+"""
+
+import time
+import random
+
+class ExponentialBackoff:
+    """An implementation of the exponential backoff algorithm
+
+    Provides a convenient interface to implement an exponential backoff
+    for reconnecting or retrying transmissions in a distributed network.
+
+    Once instantiated, the delay method will return the next interval to
+    wait for when retrying a connection or transmission.  The maximum
+    delay increases exponentially with each retry up to a maximum of
+    2^10 * base, and is reset if no more attempts are needed in a period
+    of 2^11 * base seconds.
+
+    Parameters
+    ----------
+    base: int
+        The base delay in seconds.  The first retry-delay will be up to
+        this many seconds.
+    integral: bool
+        Set to True if whole periods of base is desirable, otherwise any
+        number in between may be returned.
+    """
+
+    def __init__(self, base=1, *, integral=False):
+        self._base = base
+
+        self._exp = 0
+        self._max = 10
+        self._reset_time = base * 2 ** 11
+        self._last_invocation = time.monotonic()
+
+        # Use our own random instance to avoid messing with global one
+        rand = random.Random()
+        rand.seed()
+
+        self._randfunc = rand.rand_range if integral else rand.uniform
+
+    def delay(self):
+        """Compute the next delay
+
+        Returns the next delay to wait according to the exponential
+        backoff algorithm.  This is a value between 0 and base * 2^exp
+        where exponent starts off at 1 and is incremented at every
+        invocation of this method up to a maximum of 10.
+
+        If a period of more than base * 2^11 has passed since the last
+        retry, the exponent is reset to 1.
+        """
+        invocation = time.monotonic()
+        interval = invocation - self._last_invocation
+        self._last_invocation = invocation
+
+        if interval > self._reset_time:
+            self._exp = 0
+
+        self._exp = min(self._exp + 1, self._max)
+        return self._randfunc(0, self._base * 2 ** self._exp)