ColdFusion Enterprise Clustering: Session Replication, Sticky Sessions, and Node Failover

ColdFusion Enterprise’s built-in clustering (Enterprise, Trial, or Developer edition only — not Standard) lets you group multiple ColdFusion instances so a web-server connector distributes load and fails traffic over to healthy nodes when one stops. You configure it in ColdFusion Administrator → Enterprise Manager → Instance Manager / Cluster Manager, which writes the cluster block into each instance’s server.xml. Two session strategies exist: sticky sessions (the connector pins each client to one node via the jvmRoute suffix on the JSESSIONID — simple, but if that node dies the user's in-memory session is lost) and J2EE session replication (Tomcat multicast copies the session scope across nodes so it survives a node failure — but it requires "Use J2EE session variables" enabled on every instance, is slow to sync, generates heavy traffic, doesn't replicate arrays in session-scope CFCs, and gives no guarantee of a seamless hand-off). The critical honest truth: Adobe practitioners do not recommend in-memory multicast session replication for production — the modern, reliable answer is external session storage in Redis (CF2016+), which makes replication and sticky sessions unnecessary. This guide covers all three with verified specifics.
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