Expands and clarifies exactly what is and isn't allowed when specifying a
subset of the nodes as targets of a cluster API, and adds missing links to this
from the hot threads and cluster stats API docs.
Co-authored-by: David Turner <david.turner@elastic.co>
Co-authored-by: Yu <yu.liu003@gmail.com>
Add a new ignore_idle_threads boolean option (default true) to
/_nodes/hot_threads, to filter out threads in known idle places like
waiting on a socket select or on pulling the next task from an empty
queue.
Closes#8985Closes#8908