/prometheus
to the root URL of the Team Edition installation.
up
time metric tells you if your instance is indeed running.
process_open_fds
counts the number of files in /proc/PID/fd
directory.
This tells you how many regular files, sockets, pseudo terminals, and other processes you currently have open.
process_max_fds
reads /proc/<PID>/limits
and uses the Soft Limit from the Max Open Files row.
Interestingly, /limits
lists both soft and hard limits. The soft limit is the value the kernel enforces for the corresponding resource,
while the hard limit acts as the ceiling for the soft limit.
process_open_fds
and process_max_fds
, you can quickly
write an alert to warn you when a process hits, say, 80% of the limit: