We added a new section "activeIndexBuilds" in SERVER-57625 to capture metrics for index builds. The metrics are currently implemented as gauges, which go down to zero when there are no longer any in-progress index builds. If these metrics were converted to counters that never decrement, it may work better with some of our diagnostic tools such as FTDC and support better trend analysis.

Separately, if we decide to move forward on this change, we should consider renaming this section since "activeIndexBuilds" will not be accurate anymore. This new section would also be a suitable location for new metrics requested in SERVER-64659.

This section is new to 6.0 and has not been back ported to earlier versions of the server.