use CGI; use Fcntl qw(LOCK_EX LOCK_NB); open HIGHLANDER, ">>/tmp/renew.cgi.highlander" or die "Cannot open highlander: $!"; { my $count = 0; { flock HIGHLANDER, LOCK_EX | LOCK_NB and last; sleep 1; redo if ++$count < 10; ## couldn't get it after 10 seconds... my $host = $ENV{REMOTE_HOST}; $host = $ENV{REMOTE_ADDR} unless defined $host; warn "$0 @ ".(localtime).": highlander abort for $host after 10 seconds\n"; print CGI::header(-status => 503, -retry_after => 30, -type => 'text/plain'), "Our server is overloaded. Please try again in a few minutes.\n"; exit 0; } } ## be sure to close HIGHLANDER at end of critical region if using mod_perl