def __init__(self, options, log, stable_name, pinger=None, resolver=None):
"""Create a cache factory from settings.
:param options: Task's scoped options.
:param log: Task's context log.
:param stable_name: Task's stable name.
:param pinger: Pinger to choose the best remote artifact cache URL.
:param resolver: Resolver to look up remote artifact cache URLs.
:return: cache factory.
"""
self._options = options
self._log = log
self._stable_name = stable_name
# Created on-demand.
self._read_cache = None
self._write_cache = None
# Protects local filesystem setup, and assignment to the references above.
self._cache_setup_lock = threading.Lock()
# Caches are supposed to be close, and we don't want to waste time pinging on no-op builds.
# So we ping twice with a short timeout.
# TODO: Make lazy.
self._pinger = pinger or Pinger(timeout=self._options.pinger_timeout,
tries=self._options.pinger_tries)
# resolver is also close but failing to resolve might have broader impact than
# single ping failure, therefore use a higher timeout with more retries.
self._resolver = resolver or \
(RESTfulResolver(timeout=1.0, tries=3) if self._options.resolver == 'rest' else \
NoopResolver())
