@Override
  public void shutdown() {
    logger.info("Shutting down the BlockingChannelConnectionPool");
    for (Map.Entry<String, BlockingChannelInfo> channels : connections.entrySet()) {
      channels.getValue().cleanup();
    }
  }
A connection pool that uses BlockingChannel as the underlying connection.
It is responsible for all the connection management. It helps to
checkout a new connection, checkin an existing connection that has been
checked out and destroy a connection in the case of an error
ambry-network/src/main/java/com/github/ambry/network/BlockingChannelConnectionPool.java