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There are many algorithms or methods for distributing the load between servers. Random or round-robin are simple approaches. More sophisticated algorithms consider runtime properties in the system like the machine's load or the number of pending requests. The distribution can also be controlled by application-specific requirements like sticky sessions. With a reasonably diverse set of users, simple approaches perform as well as complex ones.
In WSO2 Carbon-based products, cluster messages are used to identify a node that is joining or leaving the cluster.
Session affinity
Stateful applications inherently do not scale well. State replication induces a performance overhead on the system. Instead of deploying stateful applications in a cluster, you can use session-affinity-based load balancing.
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