RTG Frequently Asked Questions (FAQ)
Last Updated: April 8, 2005
Table of Contents
-----------------
1. General
1.1 Where to obtain RTG?
1.2 Why did you write RTG?
1.3 Who should use RTG?
1.4 How fast is RTG?
1.5 Does RTG support SNMP v1/v2c?
1.6 Does RTG support SNMP v3 (encryption)?
1.7 Does RTG support 64-bit SNMP OIDs?
1.8 Does RTG support gauge types?
1.9 Does RTG perform any averaging?
1.10 Does RTG align the data samples?
1.11 Can you explain the default RTG database schema?
1.12 Aren't SQL databases a poor way to store time-series data?
2. Installation
2.1 Which Operating Systems does RTG run on?
2.2 Can RTG use a database other than MySQL?
2.3 Do I need to load a special MIB for device X?
3. Configuration
3.1 What is the OutOfRange setting?
4. Common Problems
4.1 SNMP errors and 64-bit counters
4.2 I'm seeing strange spikes/dips in my graphs?
4.3 RTG does not detect some of my interfaces
4.4 rtgplot images in web pages appear broken
4.5 I'm getting many out-of-range errors?
4.6 My database is corrupted!
4.7 Where to find more help
5. Miscellaneous
5.1 What does RTG stand for?
5.2 What are the future development plans for RTG?
5.3 RTG is really useful. How can I help?
5.4 Submitting code
1. General
---------------
1.1 Where to obtain RTG?
The RTG home page is: http://rtg.sourceforge.net/ Thanks to SourceForge
and Firefly Networks for their support.
1.2 Why did you write RTG?
Because other freely available traffic gathering programs:
a) did not finish polling and graphing all of our targets before the
next polling interval
b) did not retain data long enough or without averaging
c) did not provide an interface to generate complex or custom reports or
graphs
d) were resource intensive.
e) were not easily distributable
1.3 Who should use RTG?
If you have requirements to:
a) record large amounts of time-series SNMP data quickly
b) keep the data for long periods
c) generate complex reports based on the data
then RTG is a good fit. If you are simply looking to generate
weekly/monthly traffic plots, MRTG [1], RRDtool [2] or Cricket [3] are
probably better bets.
1.4 How fast is RTG?
It depends on many factors, but several hundred objects (OIDs) per second
is typical. The current RTG speed record is over 1800 objects per second.
We maintain an RTG speed record page at:
http://rtg.sourceforge.net/docs/rtgspeed.html.
1.5 Does RTG support SNMP v1/v2c?
Yes.
1.6 Does RTG support SNMP v3 (encryption)?
Not yet.
1.7 Does RTG support 64-bit SNMP OIDs?
Yes.
1.8 Does RTG support gauge types?
Yes.
1.9 Does RTG perform any averaging?
No. If your database tables are growing too large, you may wish to
implement a back-end script that averages data into other tables.
1.10 Does RTG align the data samples, say on 5 minute boundaries?
No. It is up to the supporting applications (graphers, perl reports)
to "do the right thing" and calculate the time between successive samples.
1.11 Can you explain the default RTG database schema?
Sure. Many new RTG users are confused about the default database
schema and concerned that it will not scale in their environment. As
with all database issues, the schema will be highly dependent on the
individual installation. In fact, the poller is almost completely agnostic
with regard to the actual schema. Users are encouraged to tailor the schema
based on speed, space, targets, number of tables, etc. Issues related
to the schema have been discussed on the mailing list, in particular:
http://fireflynetworks.net/pipermail/rtg/2003-July/000477.html
1.12 Aren't SQL databases a poor way to store time-series data?
That's a matter of opinion. We favor the abstract interface that a SQL
database provides to the data. This makes it easy to develop new and
custom reports quickly in any language (C, Perl DBI, PHP, etc).
2. Installation
---------------
2.1 Which Operating Systems does RTG run on?
RTG is developed on FreeBSD and tested extensively on Solaris and Linux.
RTG should compile on most UNIX boxes although autoconf doesn't always
work its magic properly. If you modify RTG to support a new platform,
please let us know. RTG does not support Windows.
2.2 Can RTG use a database other than MySQL?
Yes, RTG also supports Postgres as of version 0.8. Other databases
could quite probably be supported, but are not a current focus.
2.3 Do I need to load a special MIB for device X?
No, assuming that polling device X's OID returns a 32 or 64 bit integer
or a gauge.
3. Configuration
---------------
3.1 What is the OutOfRange setting?
The OutOfRange (OOR) setting in rtg.conf is just a sanity check to keep
bogus data from entering the database. For example, rtg is polling a
64bit OID on a router; the last value returned was 100. The router is
rebooted before the next poll. On the next poll, the router returns 50
for this OID. RTG must assume this was a counter wrap, so the delta value
is: 2^64 - 100 + 50, corresponding to approximately 4^17 bps which is
clearly impossible. This is where the OOR comes into play. It is simply
a sanity check that is set to a reasonable value. 93750000000 * 8 / 300 ~=
2.5Gbps, so most people will not want or need to adjust the OOR setting.
4. Common Problems
---------------
4.1 SNMP errors and 64-bit counters
If you receive "no such variable name" errors when polling 64-bit OIDs,
make certain you are using SNMPv2 in rtg.conf.
4.2 I'm seeing strange spikes/dips in my graphs?
First, make certain that the device was not rebooted or its counters
reset. RTG can detect counter wraps, but there is no way to detect
multiple counter wraps. With 32 bit counters and 5 minute polling
intervals, the interface cannot be running more than ~114Mbps or the
counter will wrap multiple times. Increase the polling interval or use 64
bit counters (recommended).
4.3 RTG does not detect some of my interfaces
The rtgtargmkr.pl script intentionally ignores certain interfaces listed
in the array @reserved. To debug the rtgtargmkr.pl script, set the $DEBUG
and $DBOFF variables to 1 (on).
4.4 rtgplot images in web pages appear broken
Check the web server error log first, this often reveals the source of
the problem. Make certain the web directory has CGI exec privileges.
Make certain the rtgplot binary can locate the libraries it requires.
Instructions for configuring apache are in Section 7 of the README.
4.5 I'm getting many out of range errors?
This is typically caused by a '0' in the targets file OOR column.
See also question 3.1. The next version of RTG will include a new
configuration file format to prevent this (unintentional) misconfiguration.
4.6 My database is corrupted!
This isn't an RTG-specific problem, but can occur if the database
fills or crashes (e.g. power outage). The database is typically
repaired easily, following the MySQL documentation:
http://dev.mysql.com/doc/mysql/en/Table_maintenance_SQL.html
http://dev.mysql.com/doc/mysql/en/REPAIR_TABLE.html
4.7 Where to find more help
We're all overworked. If you could, please follow these steps in order to
get more help to a particular question:
a) Read the FAQ/README/NEWS/TODO files carefully
b) Browse and search the mailing list archives:
http://rtg.sourceforge.net/docs/index.html
c) Post to the mailing list
5. Miscellaneous
---------------
5.1 What does RTG stand for?
We weren't feeling terribly creative the day we named RTG and we
intended to pay our respects to the MRTG authors, Tobias Oetiker
and Dave Rand. RTG stands for "Real Traffic Grabber." Real as
in no averaging and Grabber to show its primary functionality.
5.2 What are the future development plans for RTG?
While we've squashed most of the bugs after several releases of RTG,
there is a substantial backlog of feature requests. Rather than adding
each new feature with a separate hack, we're redesigning parts of the
poller and grapher to allow more flexibility. This redesign will allow
for unanticipated new features to be easily added. See our version 0.8
roadmap at: http://rtg.sourceforge.net/docs/rtg-0.8.html
5.3 RTG is really useful. How can I help?
Send beer! Alternatively, send us feedback so we can help improve RTG at:
http://rtg.sourceforge.net/feedback/feedback.html Coders can reference the
TODO file in the source tarball to find ways to contribute.
5.4 Submitting code
If you have written a useful {module,extension,patch,script} for RTG
that others might benefit from, please share it. Send to:
rbeverly at "users" d0t "sourceforge" d0t "net". Thanks!
References:
[1] MRTG, http://people.ee.ethz.ch/~oetiker/webtools/mrtg/
[2] RRDtool, http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/
[3] Cricket, http://cricket.sourceforge.net/