After upgrading to 7.3 over the weekend, I now have a node that constantly sits at full CPU utilization. _nodes/hot_threads is empty. The cluster has 25 indices, 250 total shards, and is made of up 3 machines, with each machine having 2 cores and 8gb of memory.
Replacing the high cpu-using node with a new machine did not fix the situation; high cpu usage came back after rebalance. Are there any known steps to fix or this is something new that was introduced in 7.3?