how can an NRPE script know the remote server's IP?

[Morty]

Is there a way for an NRPE script to know the remote server's IP?  I'm
not seeing anything in the environment for NRPE 2.12.  getpeername on
STDIN doesn't seem to help; presumably nrpe doesn't connect the script
directly to the sockets.

Detailed scenario:

I have two nagios servers running in an active/active cluster.  So
each nagios instance is checking all servers.  Some services utilize
NRPE.  One service check is a script that wants to see change in a
certain system parameter since last time.  It then saves the value in
a statefile, so it can check the next time.

Problem: race condition.  If the two nagios servers both check at
around the same time, one of them will set the state file.  Then the
other one sees the recent statefile and sees no change in the system
parameter, and the service check goes critical.

A lockfile won't solve the problem, because the problem isn't when the
two are running at the same time, it's when the two run shortly after
one another.

One fix would be to have the script use a statefile that includes the
nagios server IP.  So it would use a different statefile depending on
which nagios server queries, and there would be no conflict.  The
problem is, I can't see a way to supply the server IP to the script.
No such variable appears in the NRPE environment.  getpeername isn't
working, at least on STDIN.

I could try to do something with a nagios macro, but NRPE scripts are
supposed to have fixed options unless I turn on dont_blame_nrpe=1,
which I don't want to do.

- Morty

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