How do I stop duplicate emails being sent or broadcasted in a clustered environment?

You need to comment out the scheduler in one of the nodes. The attached document will help you figure out the next steps in the v7.x series.

A bit about clustering:

Yellowfin can be clustered on multiple servers to allow for high-availability and load-balancing. The actual load-balancing (multiplexing requests from external requests) can be achieved with a hardware load-balancer, or load-balancing software. This guide will outline the modifications required to Yellowfin's configuration to enable clustering, but not the external environment that multiplexes the incoming requests.

It is required that the load-balancing infrastructure delivers network traffic to the Yellowfin application server transparently, as if the packets were connecting directly to the application server directly. If Session Replication is not enabled, the load-balancing infrastructure will need to provide “sticky-session” functionality, where traffic for a user’s session should be sent to the same node.

Yellowfin supports clustering at 2 levels:

1. Application

2. Container 

Is article helpful?