Enable Impersonation for HBase REST Gateway

To enable HBase REST Gateway impersonation, configure all HBase servers to allow proxy users, then configure every REST Gateway to enable impersonation.

To enable REST Gateway impersonation, add the following to the hbase-site.xml file for every REST gateway:
<property>
    <name>hbase.rest.authentication.type</name>
    <value>kerberos</value>
</property>
<property>
    <name>hbase.rest.authentication.kerberos.principal</name>
    <value>HTTP/_HOST@HADOOP.LOCALDOMAIN</value>
</property>
<property>
    <name>hbase.rest.authentication.kerberos.keytab</name>
    <value>$KEYTAB</value>
</property>

Substitute the keytab for HTTP for $KEYTAB.