Tableau Server is a stateful application, meaning it maintains information about a user's session (e.g., login status, workbook interactions) on the specific node that initiated the session. When using a load balancer, it is essential to enable "sticky sessions" (also known as session affinity or persistence). This configuration ensures that all subsequent requests from a single user during their session are consistently routed to the same Tableau Server node. Without sticky sessions, a user's requests could be distributed to different nodes, leading to session loss, unexpected logouts, and a broken user experience.

A. Configuring the load balancer to use a round-robin method for distributing requests across nodes is incorrect because, without session affinity, it would break user sessions by sending subsequent requests to different nodes that do not have the original session's state.

C. Setting up the load balancer to redirect all write operations to a single node is incorrect. This is not a standard load balancer function for Tableau user traffic; the Tableau Server cluster architecture manages data and configuration consistency internally.

D. Allocating a separate subnet for the load balancer to enhance network performance is a network topology choice, not a direct requirement for ensuring session consistency, which is the core issue addressed by sticky sessions.

1. Tableau Server Documentation: In the guide for adding a load balancer

the documentation explicitly states the requirement for session persistence.

Source: Tableau Help

"Add a Load Balancer"

Reference: Under the section "Load balancer requirements

" the first point is: "Configure the load balancer for sticky sessions (also known as session affinity). Sticky sessions ensure that a user is connected to the same Tableau Server process throughout a session."

2. AWS Elastic Load Balancing Documentation: This official vendor documentation explains the concept and necessity of sticky sessions for applications that maintain session state.

Source: AWS Documentation

"Sticky sessions for your Application Load Balancer"

Reference: The "Overview" section states

"Sticky sessions are a mechanism to route requests from the same client to the same target... This is useful for servers that maintain state information in order to provide a continuous experience to clients."

3. Google Cloud Documentation: Similar to other major cloud vendors

Google's documentation on load balancing confirms the principle of session affinity for stateful services.

Source: Google Cloud

"External Passthrough Network Load Balancer overview"

Reference: In the section on "Session affinity

" it details how this feature directs all packets from the same client IP address and port to the same backend virtual machine

which is the underlying principle required for Tableau Server sessions.