You can use any load balancer in front of Knox and typically a round robin pattern works well. You will need at least 2 Knox instances to ensure HA, but I would look at your expected load and make sure the servers that are up during a failure can handle the load. For example, if you have 2 instances of Knox and one fails, can the one left active handle the load. If not, you may need 3 or more Knox instance.
I hope this helps.
Hi Eric thanks for your reply,is there any proper document you could suggest to follow.
Here are some great docs on Knox, http://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.4.0/bk_Knox_Gateway_Admin_Guide/content/ch01.htm... Also notice the guides posted by others here to help you with the setup.
The Apache Knox User's Guide contains a section (http://knox.apache.org/books/knox-0-6-0/user-guide.html#High+Availability) on using the Apache HTTP server as a load balancer for Knox. Someone familiar with another load balancer should be able to extrapolate the information provided in the Apache Knox User's Guide to setup that product.