| # Copyright 2020 The Fuchsia Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| |
| import time |
| |
| from typing import List |
| |
| |
| class Clock: |
| """A clock source, allowing faking of time in tests.""" |
| |
| def wait(self, seconds: float) -> None: |
| time.sleep(seconds) |
| |
| |
| class FakeClock(Clock): |
| """A fake Clock implementation, for testing.""" |
| |
| def __init__(self) -> None: |
| self.pauses : List[float] = [] |
| |
| def wait(self, seconds: float) -> None: |
| self.pauses.append(seconds) |
| |
| |
| class ExponentialBackoff: |
| """Track a polling period, exponentially backing off each poll.""" |
| def __init__( |
| self, |
| clock: Clock, |
| min_poll_seconds: float = 1., |
| max_poll_seconds: float = 600., |
| backoff: float = 1.4142135, |
| ): |
| self.min_poll_seconds: float = min_poll_seconds |
| self.max_poll_seconds: float = max_poll_seconds |
| self.current: float = min_poll_seconds |
| self.backoff: float = backoff |
| self.clock: Clock = clock |
| |
| def wait(self) -> None: |
| self.clock.wait(self.current) |
| self.current = min(self.current * self.backoff, self.max_poll_seconds) |
| |
