Load Monitor

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi All,
I have written a little script which I want to monitor the cpu load of the server it is on and email me if the loads gets too high. I am having some difficulty doing this because I am trying to read the current CPU loads from /proc/loadavg virtual file, but im having trouble actually using the output, as I only want to use the first number which represents the current load ... here is what I have, any help would be greatly appreciated.

#!/usr/bin/perl
%config = (
# a) Server name
        server => 'Server',
# b) Notification Email
        email => 'me@me.com',
# c) Alert level (when system load > ?)
        alert => '5'
);
system("cat /proc/loadavg");
while (<STDIN>) {
        push @loads, $_;
}
@loads = split(/ /);

if ($loads[1] > $config{'notify'}) {
    # Alert !! :)
    print "@loads";
    print "System [Alert]   Current Load = $loads[1]\n\n";
   &notify();
} else {
    print "System [OK]      Current Load = $loads[1]\n\n";
}
sub notify {
      $time = system("/bin/date");
        open (MAIL, "|/usr/sbin/sendmail -t");
                print MAIL "To: $config{'email'}";
                print MAIL "From: Load Monitor";
                print MAIL "Subject: ALERT High Load";
                print MAIL "Server Alert (Server Name $config{'server'
+})";
                print MAIL "Time: $time";
                print MAIL "$config{'server'} has exceeded the load al
+ert of $config{'alert'}";
        close(MAIL);
}
[download]

Thanks for any advice.

John

Comment on Load Monitor Download Code

Replies are listed 'Best First'.
Re: Load Monitor by monkfish (Pilgrim) on Nov 02, 2001 at 21:03 UTC
Update: Rewrote answer when I realized he wanted second load number which is an avg, not current load. Update2: In the first update, I removed the substr in the original post that was the answer because I wasn't paying attention. :( John, This should get you the values you are looking for in @load: @load = split (" ", `cat /proc/loadavg`); # Get loads @load = map {substr $_,0,1} @load; # Convert to first digit $#load =2; # Truncate array include only loads [download] By the way this is not very portable as not every unix makes /proc/loadavg available. You might try: $w = `w`; # run w and store in $w $w =~ s/^.*load average:\s+//; # Strip of junk before loads @load = split (" ", $w); # split them up @load = map {substr $_,0,1} @load; # Convert to first digit $#load =2; # Truncate array include only loads [download] And don't forget those \n in your prints or the MAIL won't make it. -monkfish (The Fishy Monk)	[reply] [d/l] [select]
Re: Load Monitor by arhuman (Vicar) on Nov 02, 2001 at 20:59 UTC
I just don't understand your : `system("cat /proc/loadavg"); while (<STDIN>) {` [download] why not just : `while (</proc/loadavg>) {` [download] UPDATE : Furthermore if it returns only one line (as I suspect) on all platforms, the loop is useless... Anyway rob_au pointed us to the right direction today with his post about Proc::ProcessTable "Only Bad Coders Code Badly In Perl" (OBC2BIP)	[reply] [d/l] [select]
Re: Load Monitor by perrin (Chancellor) on Nov 02, 2001 at 20:54 UTC
Have you looked at mon? It does a great job with this kind of thing, and it's written in easy-to-extend Perl.	[reply]
Re: Load Monitor by tfrayner (Curate) on Nov 02, 2001 at 20:57 UTC
Correct me if I'm wrong, but shouldn't you be checking `$loads[0]` rather than `$loads[1]`? Nothing else immediately stands out as being wrong :-) HTH, Tim Update: Okay, there are a few other problems. Most of them have been discussed below, so I won't reiterate (or is that preiterate?). Note however that you set $config{alert} but actually check $config{notify}. (Insert usual spiel about `use strict` here :-P) I also rewrote the /proc/loadavg access thusly: `open (LOADAVG,"/proc/loadavg"); while (<LOADAVG>) { @loads = split(/ /); }` [download] Do all that and it seems to work, on a one check per run basis.	[reply] [d/l] [select]
Re: Load Monitor by blackmateria (Chaplain) on Nov 02, 2001 at 21:02 UTC
I see two problems with your code: `system("cat /proc/loadavg")` does in fact print to `stdout`, but that doesn't mean you read its output from stdin. Instead of your cat+while loop+split combo, you want: @loads = split /\s+/, scalar `cat /proc/loadavg` ; You're using `$loads[1]` to represent the first element of the array. I think you want `$loads[0]` instead. Hope this helps!	[reply] [d/l] [select]