TestRole wraps GetRole in a test to verify if the role matches an expected role string.

NoSentinelsAvailable is returned when all sentinels in the list are exhausted (or none configured), and contains the last error returned by Dial (which may be nil).

Sentinel provides a way to add high availability (HA) to Redis Pool using preconfigured addresses of Sentinel servers and name of master which Sentinels monitor.

Slave represents a Redis slave instance which is known by Sentinel.