In a clustering environment, applying SSL does not seem as straightforward as in a single-server environment. We have a load balancer and worker nodes in a cluster, so we need to decide in which place we should enable SSL. Here are the two possible places:
The communication between users and the load balancer
The communication between the load balancer and the worker nodes
In practice, we usually enable SSL between users and the load balancer to secure their communication, and use cleartext communication between the load balancer and the worker nodes. Here is the deployment diagram:
This is reasonable because the worker nodes are usually protected by a firewall, and the purpose of using SSL is not only for encrypting communication channel, but a certificate signed by an authority can also help the customers' web browsers to verify the identity of the web server.
Enabling SSL communication between the load balancer and the worker node also creates many overheads...