Use a web browser to verify the hadoop IPC port is accessible

A quick, simple method to verify that your Hadoop / hdfs / IPC port is accessible is to simply use a web browser.  Setting up PolyBase, you'll need to create an external data source. This is where you point to the Hadoop IPC port.  PolyBase is not known for its robust error messages, so just because you created a data sources successfully does not mean it will work.

Lets say your Hadoop hdfs port has this address:

                   hdfs://192.168.1.120:8020

Simply replace hdfs with http and try to connect with a browser. Like this:

                   http://192.168.1.120:8020/

You should get the message:

       It looks like you are making an HTTP request to a Hadoop 
       IPC port. This is not the correct port for the web 
       interface on this daemon.

If you don't get this message, you'll need to work out why your Hadoop system is not responding.

Command(s) completed successfully.

PolyBase does not validate your Hadoop Location when you create a new external data source. For example, we created our new, but invalid data source with the following command. One that has a totally invalid hdfs location value:

               CREATE EXTERNAL DATA SOURCE [invalid] 
               WITH ( 
                TYPE = HADOOP
                , LOCATION = N'hdfs://192.168.1.130:8020'
                , RESOURCE_MANAGER_LOCATION = N'192.168.1.130:8050'
                )
               GO

PolyBase simple returned this value:  Command(s) completed successfully. The point, is that just because you can create a Hadoop external data source does not mean that it is valid.