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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>rsyslog vs. syslog-ng - a comparison</title></head>
<body>
<a href="features.html">back</a>
<h1>rsyslog vs. syslog-ng</h1>
<p><small><i>Written by <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a>
(2008-05-06), slightly updated 2012-01-09</i></small></p>
<p><b>This comparison page is rooted nearly 5 years in the past and has become severely
outdated since then.</b> It was unmaintained for several years and contained false
information on both syslog-ng and rsyslog as technology had advanced so much.
<p>This page was initially written because so many people asked about a comparison when
rsyslog was in its infancy. So I tried to create one, but it was hard to maintain as both
projects grew and added feature after feature. I have to admit we did not try hard to keep
it current -- there were many other priorities. I even had forgetten about this page, when I
saw that Peter Czanik blogged about its
<a href="http://blogs.balabit.com/2012/01/05/rsyslog-vs-syslog-ng/">incorrectness</a> (it must be noted
that Peter is wrong on RELP -- it is well alive). I now remember
that he asked me some time ago about this page, what I somehow lost... I guess he must have been
rather grumpy about that :-(
<p>Visiting this page after so many years is interesting, because it shows how much has changed since then.
Obviously, one of my main goals in regard to syslog-ng is reached: in 2007, I blogged that
<a href="http://blog.gerhards.net/2007/08/why-does-world-need-another-syslogd.html">the
world needs another syslogd</a> in order to have healthy competition and a greate feature
set in the free editions. In my opinion, the timeline clearly tells that rsyslog's competition
has driven more syslog-ng features from the commercial to the free edition. Also, I found
it interesting to see that syslog-ng has adapted rsyslog's licensing scheme, modular design and
multi-threadedness. On the other hand, the Balabit folks have obviously done a quicker and
better move on log normalization with what they call patterndb (it is very roughly equivalent
to what rsyslog has just recently introduced with the help of liblognorm).
<p>To that account, I think the projects are closer together than 5 years ago. I should now
go ahead and create a new feature comparison. Given previous experience, I think this does not
work out. In the future, we will probably focus on some top features, as Balabit does. However,
that requires some time and I have to admit I do not like to drop this page that has a lot of
inbound links. So I think I do the useful thing by providing these notes and removing the
syslog-ng information. So it can't be wrong on syslog-ng any more. Note that it still contains
some incorrect information about rsyslog (it's the state it had 5 years ago!). The core idea is
to start with updating the <a href="features.html">rsyslog feature sheet</a> and from there
on work to a complete comparision. Of course, feel free to read on if you like to get some sense
of history (and inspiration on what you can still do -- but more ;)).
<br><br>
Thanks,<br>
Rainer Gerhards
<p>
<table border="1">
<tbody>
<tr>
<td valign="top"><b>Feature</b></td>
<td valign="top"><b>rsyslog</b></td>
<td valign="top"><b>syslog-ng</b></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Input Sources</b><br>
</td>
</tr>
<tr>
<td valign="top">UNIX domain socket</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">UDP</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">TCP</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top"><a href="http://www.librelp.com">RELP</a></td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">RFC 3195/BEEP</td>
<td valign="top">yes (via <a href="im3195.html">im3195</a>)</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">kernel log</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">file</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">mark message generator as an
optional input</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">Windows Event Log</td>
<td valign="top">via a Windows event logging software such as
<a href="http://www.eventreporter.com">EventReporter</a>
or <a href="http://www.mwagent.com">MonitorWare Agent</a>
(both commercial software, both fund rsyslog development)</td>
<td valign="top"></td>
</tr>
<tr>
<td colspan="3" valign="top"><b><br>
Network (Protocol) Support</b><br>
</td>
</tr>
<tr>
<td valign="top">support for (plain) tcp based syslog</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for GSS-API</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to limit the allowed
network senders (syslog ACLs)</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for syslog-transport-tls
based framing on syslog/tcp connections</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">udp syslog</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">syslog over RELP<br>
truly reliable message delivery (<a href="http://blog.gerhards.net/2008/05/why-you-cant-build-reliable-tcp.html">Why
is plain tcp syslog not reliable?</a>)</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">on the wire (zlib) message
compression</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for receiving messages via
reliable <a href="http://www.monitorware.com/Common/en/glossary/rfc3195.php">RFC
3195</a> delivery</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for <a href="rsyslog_tls.html">TLS/SSL-protected
syslog</a> </td>
<td valign="top"><a href="rsyslog_tls.html">natively</a> (since 3.19.0)<br><a href="rsyslog_stunnel.html">via
stunnel</a></td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for IETF's new syslog-protocol draft</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for IETF's new syslog-transport-tls draft</td>
<td valign="top">yes<br>(since 3.19.0 - world's first implementation)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for IPv6</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">native ability to send SNMP traps</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to preserve the original
hostname in NAT environments and relay chains</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Message Filtering</b><br>
</td>
</tr>
<tr>
<td valign="top">Filtering for syslog facility and
priority</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for hostname</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for application</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for message contents</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for sending IP address</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">ability to filter on any other message
field not mentioned above (including substrings and the like)</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td>support for complex filters, using full boolean algebra
with and/or/not operators and parenthesis</td>
<td>yes</td>
<td></td>
</tr>
<tr>
<td>Support for reusable filters: specify a filter once and
use it in multiple selector lines</td>
<td>no</td>
<td></td>
</tr>
<tr>
<td>support for arbritrary complex arithmetic and string
expressions inside filters</td>
<td>yes</td>
<td></td>
</tr>
<tr>
<td valign="top">ability to use regular expressions
in filters</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for discarding messages
based on filters</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">ability to filter out messages based on sequence of appearing</td>
<td valign="top">yes (starting with 3.21.3)</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">powerful BSD-style hostname and
program name blocks for easy multi-host support</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Supported Database Outputs</b><br>
</td>
</tr>
<tr>
<td valign="top">MySQL</td>
<td valign="top"><a href="rsyslog_mysql.html">yes</a>
(native ommysql, <a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">PostgreSQL</td>
<td valign="top">yes (native ompgsql, <a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">Oracle</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">SQLite</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">Microsoft SQL (Open TDS)</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">Sybase (Open TDS)</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">Firebird/Interbase</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">Ingres</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">mSQL</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top"></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Enterprise Features</b><br>
</td>
</tr>
<tr>
<td valign="top">support for on-demand on-disk
spooling of messages</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to limit disk space used
by spool files</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">each action can use its own,
independant
set of spool files</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">different sets of spool files can
be placed on different disk</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to process spooled
messages only during a configured timeframe (e.g. process messages only
during off-peak hours, during peak hours they are enqueued only)</td>
<td valign="top"><a href="http://wiki.rsyslog.com/index.php/OffPeakHours">yes</a><br>
(can independently be configured for the main queue and each action
queue)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to configure backup
syslog/database servers </td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td>Professional Support</td>
<td><a href="professional_support.html">yes</a></td>
<td></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Config File</b><br>
</td>
</tr>
<tr>
<td valign="top">config file format</td>
<td valign="top">compatible to legacy syslogd but
ugly</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to include config file from
within other config files</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td height="25" valign="top">ability to
include all config files
existing in a specific directory</td>
<td height="25" valign="top">yes</td>
<td height="25" valign="top"></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Extensibility</b><br>
</td>
</tr>
<tr>
<td valign="top">Functionality split in separately
loadable
modules</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">Support for third-party input
plugins</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
</tr>
<tr>
<td valign="top">Support for third-party output
plugins</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Other Features</b><br>
</td>
</tr>
<tr>
</tr>
<tr>
<td valign="top">ability to generate file names and
directories (log targets) dynamically</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">control of log output format,
including ability to present channel and priority as visible log data</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr><td valign="top">native ability to send mail messages</td>
<td valign="top">yes (<a href="ommail.html">ommail</a>, introduced in 3.17.0)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">good timestamp format control; at a
minimum, ISO 8601/RFC 3339 second-resolution UTC zone</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to reformat message
contents and work with substrings</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for log files larger than
2gb</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for log file size
limitation
and automatic rollover command execution</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">support for running multiple
syslogd instances on a single machine</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to execute shell scripts on
received messages</td>
<td valign="top"></td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">ability to pipe messages to a
continously running program</td>
<td valign="top"></td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">massively multi-threaded for
tomorrow's multi-core machines</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to control repeated line
reduction ("last message repeated n times") on a per selector-line basis</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">supports multiple actions per
selector/filter condition</td>
<td valign="top">yes</td>
<td valign="top"></td>
<td></td>
</tr>
<tr>
<td valign="top">web interface</td>
<td valign="top"><a href="http://www.phplogcon.org">phpLogCon</a><br>
[also works with <a href="http://freshmeat.net/projects/php-syslog-ng/">
php-syslog-ng</a>]</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">using text files as input source</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">rate-limiting output actions</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">discard low-priority messages under
system stress</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td height="43" valign="top">flow control
(slow down message reception when system is busy)</td>
<td height="43" valign="top">yes (advanced,
with multiple ways to slow down inputs depending on individual input
capabilities, based on watermarks)</td>
<td height="43" valign="top"></td>
</tr>
<tr>
<td valign="top">rewriting messages</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">output data into various formats</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">ability to control "message
repeated n times" generation</td>
<td valign="top">yes</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">license</td>
<td valign="top">GPLv3 (GPLv2 for v2 branch)</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">supported platforms</td>
<td valign="top">Linux, BSD, anecdotical seen on
Solaris; compilation and basic testing done on HP UX</td>
<td valign="top"></td>
</tr>
<tr>
<td valign="top">DNS cache</td>
<td valign="top"></td>
<td valign="top"></td>
</tr>
</tbody>
</table>
<p>While the <span style="font-weight: bold;">rsyslog</span>
project was initiated in 2004, it <span style="font-weight: bold;">is
build on the main author's (Rainer Gerhards) 12+ years of
logging experience</span>. Rainer, for example, also
wrote the first <a href="http://www.winsyslog.com/Common/en/News/WinSyslog-1996-03-31.php">Windows
syslog server</a> in early 1996 and invented the <a href="http://www.eventreporter.com/Common/en/News/EvntSLog-1997-03-23.php">eventlog-to-syslog</a>
class of applications in early 1997. He did custom logging development
and consulting even before he wrote these products. Rsyslog draws on
that vast experience and sometimes even on the code.</p>
<p>Based on a discussion I had, I also wrote about the <b>political
argument why it is good to have another strong syslogd besides syslog-ng</b>.
You may want to read it at my blog at "<a href="http://rgerhards.blogspot.com/2007/08/why-does-world-need-another-syslogd.html">Why
does the world need another syslogd?</a>".</p>
<p>[<a href="manual.html">manual index</a>]
[<a href="rsyslog_conf.html">rsyslog.conf</a>]
[<a href="http://www.rsyslog.com/">rsyslog site</a>]</p>
<p><font size="2">This documentation is part of the
<a href="http://www.rsyslog.com/">rsyslog</a> project.<br>
Copyright © 2008 by <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a> and
<a href="http://www.adiscon.com/">Adiscon</a>. Released under the GNU GPL
version 2 or higher.</font></p>
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