Add watchdog to monitor VM cpu load and reset for excessive load

Detect if VM is running under excessive load (e.g., due to fork bombing)
for longer than a certain period and reset the VM state if so.

doc/MODULES

@@ -14,6 +14,7 @@ LWP::Simple
 LWP::UserAgent
 LWP::UserAgent::WithCache
 Net::Dict
+Proc::ProcessTable
 SOAP::Lite
 Text::Autoformat
 Text::Balanced

modules/compiler_vm/compiler_server_watchdog.pl

@@ -0,0 +1,59 @@
+#!/usr/bin/env perl
+
+use warnings;
+use strict;
+
+use Proc::ProcessTable;
+use IO::Socket;
+
+my $SLEEP = 15;
+my $MAX_PCTCPU = 25;
+my $QEMU = 'qemu-system-x86';
+my $MONITOR_PORT = 3335;
+
+my $last_pctcpu = 0;
+
+sub reset_vm {
+  print "Resetting vm\n";
+
+  my $sock = IO::Socket::INET->new(PeerAddr => '127.0.0.1', PeerPort => $MONITOR_PORT, Prot => 'tcp');
+  if(not defined $sock) {
+    print "[vm_reset] Unable to connect to monitor: $!\n";
+    return;
+  }
+
+  print $sock "loadvm 1\n";
+  close $sock;
+
+  print "Reset vm\n";
+}
+
+while (1) {
+  my $t = new Proc::ProcessTable(enable_ttys => 0);
+
+  my ($pids, $p);
+
+  foreach $p (@{$t->table}) {
+    $pids->{$p->pid} = { fname => $p->fname, ppid => $p->ppid };
+  } 
+
+  foreach $p (keys %$pids) {
+    if ($pids->{$p}->{fname} eq $QEMU) {
+      my $ppid = $pids->{$p}->{ppid};
+      if ($pids->{$ppid}->{fname} eq 'compiler_server') {
+        my $pctcpu = `top -b -n 1 -p $p | tail -n 1 | awk '{print \$9}'`;
+        $pctcpu =~ s/^\s+|\s+$//g;
+        print scalar localtime, " :: Got compiler qemu pid: $p; using $pctcpu cpu\n";
+
+        if ($pctcpu >= $last_pctcpu and $last_pctcpu >= $MAX_PCTCPU) {
+          reset_vm;
+          $last_pctcpu = 0;
+        } else {
+          $last_pctcpu = $pctcpu;
+        }
+      }
+    }
+  }
+
+  sleep $SLEEP;
+}