Question

In a system requiring horizontal scaling, which load balancing algorithm ensures that requests from the same client session are consistently directed to the same server node based on a hash of the client identifier?

Accepted Answer

The load balancing algorithm that ensures requests from the same client session are consistently directed to the same server node is called Source IP Hashing or Session Affinity Hashing. This process works by taking a unique identifier from the incoming request, such as the client&#x27;s IP address or a session ID, and applying a mathematical hash function to it. A hash function is an algorithm that converts data of any size into a fixed-length string of characters or a specific number. The resulting hash value acts as a digital fingerprint for that client. The load balancer then performs a modulo operation on this hash value using the number of available servers to determine a specific target node index. Because the same input consistently generates the same hash, the load balancer will map the same client identifier to the same server every time, provided the total number of servers remains constant. This technique is essential for stateful applications where a server must maintain data regarding a user&#x27;s progress, such as an e-commerce shopping cart, because it ensures that subsequent requests from the same user are handled by the same server where the session data is stored.

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In a system requiring horizontal scaling, which load balancing algorithm ensures that requests from the same client session are consistently directed to the same server node based on a hash of the client identifier?