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Network Traffic Monitoring with RRDTool
This page details the use of RRDTool for
monitoring the network traffic through one or more network interfaces.
Background
See my Installing RRDTool page for detailed info on
installing and configuring RRDTool.
Note that this page assumes all directories and installation locations are
as per the page mentioned above.
If your configuration is different, you may need to adjust some parts of the installation instructions appropriately.
Screen Shots
Here's a screen shot of the graphs page. This page displays daily, weekly,
monthly and yearly trends for the traffic through the specified network interface.
the graphs page, showing daily, weekly, monthly, yearly graphs
Requirements
You'll need:
-
a Linux box
-
a web server running on the Linux box
- a working installation of RRDTool
-
my eth0.pl script for data collection
and graph generation
-
my eth0.cgi webpage for viewing the graphs
-
an SCP client (such as WinSCP,
or SSH Secure File Transfer Client, part of
SSH Secure Shell)
for copying files onto your linux box.
-
a way of getting a command-line prompt on your linux box
(either by logging directly onto your linux box,
using a SSH client such as
PuTTY
or SSH Secure Shell).
Note that I'm using a custom installation of
Red Hat 7.3 linux.
If your configuration is different, you may need to adjust some parts of the script
appropriately.
Creating a Database
I'm using a separate RRD database to hold the traffic details for each
network interface. Run the command below for each interface for which you
want to monitor network traffic, adjusting the filename appropriately.
rrdtool create /var/lib/rrd/eth0.rrd -s 300 \
DS:in:DERIVE:600:0:1500000 \
DS:out:DERIVE:600:0:1500000 \
RRA:AVERAGE:0.5:1:576 \
RRA:AVERAGE:0.5:6:672 \
RRA:AVERAGE:0.5:24:732 \
RRA:AVERAGE:0.5:144:1460
This will create an RRD database with the following attributes:
5 minute step (base interval with which data will be fed into the RRD)
2 data sources (in, and out)
10 minute heartbeat for each data source
2 days of 5 minute averages
2 weeks of 1/2 hour averages
2 months of 2 hour averages
2 years of 12 hour averages
Refer to the
rrdcreate manpage for more information on these options.
Getting Data
The next task is to determine how to obtain the data we want to insert
into the RRD database.
Some shell scripting can easily be used to obtain the items of information
required. The statements below will return the bytes in and out
respectively for the specified interface (eth0):
ifconfig eth0 |grep bytes|cut -d":" -f2|cut -d" " -f1
ifconfig eth0 |grep bytes|cut -d":" -f3|cut -d" " -f1
Run these from a command prompt to verify they return some rather large numbers.
Note that these numbers are the cumulative total throughput of the interface.
These totals will wrap around, and start again at zero, but RRDTool only
looks at the difference in the value since the last time an update was
performed.
According to the RRDTool
documentation,
you're supposed to use COUNTER for these types of data,
but I've found RRDTool generates large spikes in the trends if the traffic counters
are unexpectedly reset (ie, when you reboot your linux box).
Using DERIVE doesn't assume an overflow if the counter value
has decreased, eliminating the spikes. However, it can mean you'll get
a value of zero (which is perferable to a large spike, as the spike tends
to upset the scale of the graphs).
Automating Data Collection
To automate data collection, I wrote a Perl script which performs the following tasks:
retrieve data
push data into the RRD database
generate daily, weekly, monthly and yearly graphs
You can download a copy of my
eth0.pl script.
Rename it to eth0.pl, and save it in
/etc/rrd/.
Make it executable by changing the file permissions on it:
chmod 755 /etc/rrd/eth0.pl
and adjust the settings defined at the top of the script to make them appropriate
for your linux box, including the interface name, and the interface description:
# define location of rrdtool binary
my $rrdtool = '/usr/bin/rrdtool';
# define location of rrdtool databases
my $rrd = '/var/lib/rrd';
# define location of images
my $img = '/var/www/html/rrdtool';
# define the network interface
my $iface = 'eth0';
# define a description for the interface
my $descr = 'local ethernet';
Test the script by executing it from a command prompt:
/etc/rrd/eth0.pl
and you should see output similar to this:
[root rrd]# /etc/rrd/eth0.pl
eth0 traffic in, out: 2472152778, 477181472
Once you've verified the operation of the script, it can be automatically
scheduled to run periodically. To get it to run every 5 minutes,
add the following to
/etc/crontab:
# get eth0 traffic details
*/5 * * * * root /etc/rrd/eth0.pl > /dev/null
Note that if you find your graphs are being created, but with no data,
you'll have to either:
edit /etc/rrd/eth0.pl to reference the full pathname
for ifconfig, cut and
grep,
or
edit the PATH
definition in /etc/crontab to include the
paths of those commands.
Viewing the Graphs
Each time the script is executed, if required, it'll update the graphs of
SNR, signal, noise and the link rate.
These graphs are being created in /var/www/html/rrdtool/,
and assuming you've got a webserver running, they'll be accessible via
http://your_ip/rrdtool/.
To provide a much cleaner way to view these graphs, I've written a single
webpage for displaying all the trends.
You can download a copy of my
eth0.cgi webpage.
Rename it to eth0.cgi, and save it in
/var/www/html/rrdtool/.
Make it executable by changing the file permissions on it:
chmod 755 /var/www/html/rrdtool/eth0.cgi
and adjust the settings defined at the top of the script to make them appropriate
for your linux box, in particular, the interface name:
# define the network interface
my $iface = 'eth0';
# define the network inteface description
my $descr = 'local ethernet';
# get the server name (or you could hard code some description here)
my $svrname = $ENV{'SERVER_NAME'};
Note that I'm assuming you've got your web server appropriately configured
to handle .cgi scripts. if not, refer to the
inline documentation in your httpd.conf or the Apache
documentation for more information.
You should now be able to point your web browser at
http://your_ip/rrdtool/eth0.cgi and you should
be rewarded with a page displaying the traffic graphs for the specified interface.
What's Next?
You can easily extend the code shown above to monitor traffic on additional
interfaces.
It's just a matter of creating an RRD database for each additional interface,
copy the eth0.pl script, ajust the interface name
and description, schedule it, and copy and edit the webpage to view the graphs.
References
Installing RRDTool
Wireless Link Monitoring with RRDTool
About RRD Tool
RRD Tool Manual
last updated 27 Dec 2003
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