When AbstractRpcClient calls getConnection, the status of conn should be checked

/**
 * Get a connection from the pool, or create a new one and add it to the pool. Connections to a
 * given host/port are reused.
 */
private T getConnection(ConnectionId remoteId) throws IOException {
  if (failedServers.isFailedServer(remoteId.getAddress())) {
    if (LOG.isDebugEnabled()) {
      LOG.debug("Not trying to connect to " + remoteId.getAddress()
        + " this server is in the failed servers list");
    }
    throw new FailedServerException(
      "This server is in the failed servers list: " + remoteId.getAddress());
  }
  T conn;
  synchronized (connections) {
    if (!running) {
      throw new StoppedRpcClientException();
    }
    conn = connections.getOrCreate(remoteId, () -> createConnection(remoteId));
    conn.setLastTouched(EnvironmentEdgeManager.currentTime());
  }
  return conn;
} 

@Override
public boolean isActive() {
  return channel != null && channel.isActive();
}