why do you want to decommission a node as part of the data center power down event? Typically H.A. is setup to automatically failover the dataengine and the repository upon the active becoming not available. If there is a need to take down the entire data center, then you have two options, you can script a tabadmin stop prior to the power down and then a tabadmin start upon a power up. Or you could create a DNS switch that permits failing over to a completely separate DR cluster in a separate data center.
It is a planned power down event in one of our data center. I do not have separate DR cluster so planning this ahead of time before the event. We have two worker nodes that span across our two data centers for H/A. I know tableau does not recommend this but it works for us coz our data centers are only 50 miles apart and we have synchronous replication in place and latency is not a concern. Tableau automatic fail over is not reliable at times when the node goes down abruptly. Is there any way to do "tabadmin stop worker_node" so that i don't have to mess up with the configuration? That way I will bring down the node before the power down event starts and let tableau fail over automatically to other worker node?
That makes a little more sense, it's good to hear of an instance where TS is split across data centers. Though, I think you may be blazing new territory here, and if it works, more power to you.
One option for stopping the worker node, though TOTALLY unendorsed from Tableau and needs to be tested out, is to create a windows script to stop the Tableau Service on the worker node. To test it out, you can go to services manually and stop it. And then start it to see if the cluster will become whole again, or you may need to do a restart on the primary.