Major Description
ServerManager#getServerConnection() try to retrieve the cached connection from Map serverConnections. ServerName objects are the key with which items are saved in this map. But we use String type to get. This always returns null and in turn the Master creates a new connection with RS again and again.
private final Map<ServerName, HRegionInterface> serverConnections = new HashMap<ServerName, HRegionInterface>(); ........... private HRegionInterface getServerConnection(final ServerName sn) throws IOException { HRegionInterface hri = this.serverConnections.get(sn.toString()); if (hri == null) { LOG.debug("New connection to " + sn.toString()); hri = this.connection.getHRegionConnection(sn.getHostname(), sn.getPort()); this.serverConnections.put(sn, hri); } return hri; }