Creating RRD graphs for TME Ethernet thermometer TME_C_EU pt1

So I decided to buy one of these network temperature sensors from Papouch here to monitor my 19" rack at home. I wanted to graph the temperature variations from it, as it can get quite hot when all the other servers are on.

Setup Apache with mod_php5 + rrd+ php5_cli

There are many articles on setting up apache + mod_php5 + rrdtools + php5_cli, so i won't bother you with the details here.

Create the RRD

One you've installed rrdtool and php5 cli, create the below file and chmod a+x so that it is executable.

Once run, this will create your RRD to input data called temp.rrd

#!/usr/bin/php

<?
echo "Creates blank temp graphs";
$options = array (
 "--step", "60",            // Use a step-size of 1 minute
 "--start", "-1 day",     // this rrd started 6 months ago
 "DS:temp:GAUGE:100:U:U",
"RRA:MIN:0.5:60:8800",
"RRA:MAX:0.5:60:8800",
"RRA:AVERAGE:0.5:2:328800",
);


$ret = rrd_create("./temp.rrd", $options);
if (! $ret) {
 echo "<b>Creation error: </b>".rrd_error()."\n";
}

?>

Create the graphs

This should be your index.php This should be in your /var/www directory

<?

create_graph_temperature("/var/www/temp-hr.gif","-1h","Hourly temperature");
create_graph_temperature("/var/www/temp-2hr.gif","-2h","Bi-Hourly temperature");
create_graph_temperature("/var/www/temp-daily.gif","-23h","Daily temperature");
create_graph_temperature("/var/www/temp-weekly.gif","-1w","Weekly temperature");
create_graph_temperature("/var/www/temp-monthly.gif","-1m","Monthly temperature");
create_graph_temperature("/var/www/temp-yearly.gif","-1y","Yearly temperature");

function create_graph_temperature ($output, $start, $title)
{
    $options = array(
    "--slope-mode",
    "--start", $start,
    "--title=$title",
    "--vertical-label=Temperature in oC",
    "DEF:temp=/mnt/ramdisk/temp.rrd:temp:AVERAGE",
    "CDEF:ttemp=temp,1,*",
    "CDEF:ttempq=temp,6,/",
    "AREA:ttempq#F31616::STACK",
    "AREA:ttempq#F03D11::STACK",
    "AREA:ttempq#ED650D::STACK",
    "AREA:ttempq#EA8D08::STACK",
    "AREA:ttempq#E7B504::STACK",
    "AREA:ttempq#E5DD00::STACK",
    "COMMENT:\\n",
    "GPRINT:temp:MAX:Max temp %6.2lf",
    "GPRINT:temp:MIN:Min temp %6.2lf",
    "GPRINT:temp:AVERAGE:Avg temp %6.2lf",
        );
    $ret = rrd_graph($output, $options);
        if (! $ret) {
        echo "<b>Graph error for temp</b>".rrd_error()."\n";
        }
}


?>

<img src=temp-hr.gif><img src=temp-2hr.gif></br>
<img src=temp-daily.gif><img src=temp-weekly.gif></br>
<img src=temp-monthly.gif><img src=temp-yearly.gif></br>

Note:you may need to chgrp www-data and chmod g+w on the /var/www directory, so that apache can write the GIFs to there. 

Update data into RRD

Do to this, I wrote a small PHP script

#!/usr/bin/php
<?
 // Fetch current time
    $t = time();
    $filename="/mnt/ramdisk/temp.txt";

    $handle = fopen($filename, "r");
    $contents = fread($handle, filesize($filename));
    fclose ($handle);
    $contents=(float)$contents/10;
    $option = array ("$t:$contents");
    echo "$t ,$contents";
    $ret = rrd_update("/mnt/ramdisk/temp.rrd", $option);

    if (! $ret) {
    mail ("blah@gmail.com","temp insert rrd error","trying to insert temp from temp.txt into temp.rrd");
        #echo "<b>Graph error: </b>".rrd_error()."\n";
    }


?>

Crontab

I've set up my TME_C on IP address 192.168.2.120

Note I've saved the output to a ramdisk (as my machine boots from a USB key)

 crontab -e on root

* * * * * /usr/local/bin/update_temp_script.sh

Note you should be calling a script which does the update, then inserts it into the RRD in sequence. If you don't it maybe updating the RRD with blank values.

update_temp_script.sh

/usr/bin/curl -s http://192.168.2.120/fresh.xml | grep sns  | awk '{print $10}' | cut -d "\"" -f 2 > /mnt/ramdisk/temp.txt 

/usr/local/bin/update_temp.php

That's it - it's that simple.
You should have graphs looking similar to this:

Now you can also setup a daily cron job to tar.gz these files to the local file system instead of leaving it on a ramdisk or what not. If you leave it on the ramdisk, you'll lose it if the server powers it off.

part 2 here

NOTE - Have corrected this as i was only storing about 1/5 of the data, so have upped the data storage points on the RR. This was calculated at one data point every 60 seconds. So 60 seconds in 24 hrs = 1440 points.
Hourly points for a year = 366 *24 = 8784 points. I rounded this to 8800