Solaris + Tcl + Apache + RRDtool = ??

It is S.T.A.R and it shines!

My colleague wants to visualise the trend of some sampling data. Back in my mind there is this voice keep telling me to crank out a demo to prove how all these wonderful opensource can do. So, I came up with a web-form to take in the raw sampling data and plot them out dynamically. Here are the stuff that I used for this little toy:

• Solaris 10 and we run everything from a spare root zone
• Tcl (Tool Command Language), my favourite scripting langauge. My friends used to call that "Talk Cock Language".
• Apache 1.3.x (comes with Solaris 10)
• RRDtool, a very powerful data logging and graphing toolkit. Blindings for Perl, Python, Ruby and Tcl are built-in in the source tarball.

Enclosed some screen dump:

The Tcl cgi script:

package require cgi
package require Rrd


cgi_input
set ds     [cgi_import ds]
set step   [cgi_import step]
set type   [cgi_import type]
set title  [cgi_import title]
set ylabel [cgi_import ylabel]
set data   [string trim [cgi_import data]]



# find out the start time (t0) and end time (t2)
set t1 [lindex [split [lindex $data 0] :] 0]
set t2 [lindex [split [lindex $data end] :] 0]

set ndata [llength [split $data "\n"]]


#
set start [expr $t1 - 10]
set end [expr $t2 + 10]
set rrdfile  "/tmp/[file tail $argv0]-[pid].rrd"
set heartbeat [expr $step * 2]


set DS {}
foreach i [split $ds { ,}] {
        set var [string trim $i]
        append DS "DS:$var:$type:$heartbeat:U:U "
}
eval Rrd::create $rrdfile --step $step --start $start \
        $DS RRA:AVERAGE:0.5:1:$ndata


foreach d [split $data "\n"] {
        Rrd::update $rrdfile $d
}


set DEFS {}
foreach i [split $ds { ,}] {
        set var [string trim $i]
        append DEFS "DEF:$i=$rrdfile:$i:AVERAGE "
}
set LINES {}
set color {
        ff0000 00ff00 0000ff ffff00 ff00ff 00ffff
        880000 008800 000088 888800 880088 008888
}
set ncolor [llength $color]
set cnt 0
foreach i [split $ds { ,}] {
        set c [lindex $color [expr $cnt % $ncolor]]
        set var [string trim $i]
        append LINES "LINE:$i#$c:$i "
        incr cnt
}


puts "Content-type: image/png\n"
eval Rrd::graph - --imgformat PNG --star $t1 --end $t2 \
        --title \"$title\" --vertical-label \"$ylabel\" \
        $DEFS $LINES


file delete -force $rrdfile