A NNFailoverProxyProvider implementation which works on IP failover setup.
Only one proxy is used to connect to both servers and switching between
the servers is done by the environment/infrastructure, which guarantees
clients can consistently reach only one node at a time.
Clients with a live connection will likely get connection reset after an
IP failover. This case will be handled by the
FailoverOnNetworkExceptionRetry retry policy. I.e. if the call is
not idempotent, it won't get retried.
A connection reset while setting up a connection (i.e. before sending a
request) will be handled in ipc client.
The namenode URI must contain a resolvable host name.