_cat/nodes used to return `c` for client node or `d` for data node as part of the node.role column. This commit changes it to return `m` for master eligible, `d` for data and/or `i` for ingest. A node with no explicit roles will be a coordinating only node and marked with `-`. A node can obviously have multiple roles. The master column has been adapted to return only whether a node is the current master (`*`) or not (`-`).
This commit adds basic support to track the number of times scripts are
compiled and compiled scripts are evicted from the script cache. These
statistics are tracked at the node level.
Closes#12673
cat/nodes currently does not report any details related to file descriptors. This adds the current number in use, the maximum number available as well as their ratio (percentage) to cat/nodes as hidden-by-default metrics. In addition, this also adds current heap usage (as a non-percentage of ts max) and ram usage (as a non-percerntage of its max) to allow tools to provide more granularity.
Closes#7652
Adds a table with the exhaustive list of all available headers with a brief description (mostly from `org.elasticsearch.rest.action.cat.RestNodesAction`) so that people do not need to go searching for them in the code like I did, or search through `nodes?help`.
javanna
Alexander Kazakov
Henrik Nordvik
Jason Tedor
Clinton Gormley
Martijn van Groningen
Erik Ringsmuth
Chris Earle
mikemccand
Areek Zillur
Chris Earle
Andrew Raines