On this page I describe how I set up a desktop monitoring system for the status of my beamline at NSLS. I want something of the "desktop applet" variety to display the status of the NSLS ring in a manner that is always present and always visible on my desktop.
The solution I came up with uses Conky, a lightweight system monitor for Linux and BSD. Conky is not very flashy and it does not integrate visually with KDE, GNOME, or any other desktop. On the other hand, it is easy to configure and easy to extend. Building NSLS monitoring tools required a few lines of perl and some simple manipulations of the Conky configuration file.
The NSLS monitoring components make use of resources available at the NSLS machine status and history web page. Each of these is implemented as a short perl script making use of the excellent LWP package for web programming. Each script ends by printing a short message to standard output. It is this message that gets displayed in Conky.
This monitor reads one of the "device reading" channels, which are simple HTTP tools to provide almost-real-time feedback of a few selected ring parameters. It prints "yes" or "no" if beam is or is not available.
#!/usr/bin/perl
use strict;
use warnings;
use LWP::Simple;
my $xbeamavail = get 'http://status.nsls.bnl.gov/Status/Readback/xbeamavail';
my $available = sprintf("%d", $xbeamavail);
($available) ? print 'yes' : print 'no';This monitor reads another of the "device reading" channels, this one with the amount of current in the ring.
#!/usr/bin/perl
use strict;
use warnings;
use LWP::Simple;
my $xrcurr = get 'http://status.nsls.bnl.gov/Status/Readback/xrcurr';
my $current = (split(" ", $xrcurr))[0];
print $current;This monitor probes whether the X23A2 safety shutter is open or closed. This is a bit silly. There is no direct way of determining this that I know of. What I do is download the image from the X-ray ring status page. I then examine a pixel somewhere in the box indicating the state of my safety shutter. If that pixel is green, then this little script prints "open". If the pixel is some other color, it prints "closed". I use the Image::Imlib2 module from CPAN to examine the state of the pixel in the gif image.
#!/usr/bin/perl
use strict;
use warnings;
use autodie qw(open close);
use Image::Imlib2;
use LWP::Simple;
my $gif = get 'http://status.nsls.bnl.gov/Status/images/Xstat.gif';
open my $G, ">/home/bruce/.conky/Xstat.gif";
print $G $gif;
close $G;
my $i = Image::Imlib2->load("/home/bruce/.conky/Xstat.gif");
# this is a pixel in X23A2's box
my ($r, $g, $b, $a) = $i->query_pixel(653,279);
(($r == 0) and ($g == 255) and ($b == 0)) ? print "open" : print "closed";== Putting it all together ==
I then put the following lines in my Conky configuration file. These lines tell Conky to run the beam availability and current monitors every 2 minutes (120 seconds) and to run the shutter monitor every 5 minutes. These are on fairly long intervals just to keep traffic to the NSLS server down to a reasonable level.
$stippled_hr
${alignc}${color2}NSLS X-ray status
${color black}Beam available: ${alignr}$color${execi 120 ~/.conky/nsls_available.pl}
${color black}Current: ${alignr}$color${execi 120 ~/.conky/nsls_current.pl}
${color black}X23A2 Shutter: ${alignr}$color${execi 600 ~/.conky/nsls_shutter.pl}
$stippled_hr
Here is what Conky looks like on my desktop. The NSLS monitors can be seen near the top. Current had recently returned (hence the value above 300 mA), but beam had not yet been announced.
