mod_measure_process: Report the enforced limit The soft limit is what the kernel actually enforces, while the hard limit is is how far you can change the soft limit without privileges. Unless the process dynamically adjusts the soft limit, knowing the hard limit is not as useful as knowing the soft limit. Reporting the soft limit and the number of in-use FDs allows placing alerts on expressions like 'process_open_fds / process_max_fds >= 0.95'

--- a/mod_measure_process/mod_measure_process.lua	Tue Jan 18 17:01:18 2022 +0000
+++ b/mod_measure_process/mod_measure_process.lua	Tue Jan 18 18:55:20 2022 +0100
@@ -67,7 +67,7 @@
 		if has_posix then
 			local ok, soft, hard = posix.getrlimit("NOFILE")
 			if ok then
-				max_fds:set(hard)
+				max_fds:set(soft or hard);
 			end
 		end
 	end);