Question

Can anyone suggest some reading material or a tutorail how to set up a load balancer on cluster and use it with any service?

1)Can we use loadbalancer setup alone as a single entry-point for users and for callbacks from any service ? or does it have to be used with any other?

  1. Does the servers pointing to loadbalancer need to be configured to virtual IP so that request from http , or https gets served? or the http/https request can be pointed directly to loadbalancer without a virtual IP as discussed above?

  2. The load balancer should be configured for round-robin between the servers to distribute the requests, is it a feature of load balancer ?

4)In order to have full HA, the load balancer should also have HA support, or it becomes a single point of failure? Are they any open source stack available with this feature and can you suggest a few ?

  1. When you set up for group of same servers have a Round-Robin DNS do you still need a loadbalancer to serve over http and https?

Please let me know if my questions make sense or suggest an idea and literature to go through.

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For the first answer to your question, Yes you can configure a loadbalancer as a single entry point for users ( clients ). Typically a loadbalancer sits in a DMZ zone and routes service requests to the internal nodes ( internal servers ). Hardware loadbalancer does support service call backs but they will be quite expensive. I have worked with HA proxy and it works like a charm and since its open source as well so there you go! You can find lot of articles on internet for free, I will provide the link at the end of my answer.

You second question is not clear to me but still here is my take on that!

Normally, you can offload your servers to your loadbalancer, so the request from the client to the loadbalancer uses SSL and from there onwards you can use simple HTTP .i.e from your loadbalancer to your internal node. Confusing? Client --> Loadbalancer ( HTTPS)—> (HTTP) Internal node. Now you are saving your computing resources as well and serving secure requests faster. Hope you are clear with the concept.

Loadbalancer supports different algorithms for loadbalancing like srouce based, least connection, round robin and ratio based load balancing (typically supported by hardware loadbalancers), most of them are supported by HAproxy.

HAproxy supports full HA, it can be used along with keepalived ( open source tool for hearbeat sharing). You can configure two linux machines with HAproxy with Keepalived.

DNS loadbalancing can help you will IP based load balancing but when you need service based load balancing, you need a load balancing software like HAproxy. So, the answer is yes you need a load balancer for it.

Below are some links which can help you brushing up your concepts of load balancing with self sufficient tutorials.

https://www.digitalocean.com/community/tutorials/an-introduction-to-haproxy-and-load-balancing-concepts

https://www.digitalocean.com/community/tutorials/how-to-set-up-highly-available-haproxy-servers-with-keepalived-and-floating-ips-on-ubuntu-14-04

https://www.digitalocean.com/community/tutorials/how-to-create-a-high-availability-haproxy-setup-with-corosync-pacemaker-and-floating-ips-on-ubuntu-14-04

You can also refer to official documentation of HAproxy.

http://www.haproxy.org/#docs

Let me know in case I can be of any help.