hosts.py 文件源码

def __init__(self, host_provider, expire_time=600, retry_time=60,
                 invalidation_threshold=0.2):
        """Initialize the host selection.

        Args:
            host_provider: A ``HostProvider``, used to get the current list
                of live hosts.
            expire_time: An integer, expire time in seconds.
            retry_time: An integer, retry time in seconds.
            invalidation_threshold: A float, when the number of entries
                being invalidated divided by the number of all valid hosts
                is above this threshold, we stop accepting invalidation
                requests. We do this to stay on the conservative side to
                avoid invalidating hosts too fast to starve requests.

        """
        assert host_provider.initialized
        # Current host.
        self._current = None
        # Last host, works even when current host invalided.
        self._last = None
        # Time when we selected the current host.
        self._select_time = None
        # Adjust expire time by +/- 10%, but 0 is special for testing purpose.
        self._expire_time = expire_time
        if expire_time:
            self._expire_time = expire_time + int(
                random.triangular(-expire_time * 0.1, expire_time * 0.1))
        self._retry_time = retry_time
        self._invalidation_threshold = invalidation_threshold
        # Host name -> time when marked bad.
        self._bad_hosts = {}
        self._host_provider = host_provider