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diff --git a/doc/Makefile.am b/doc/Makefile.am index 0703b8fc..62ec7500 100644 --- a/doc/Makefile.am +++ b/doc/Makefile.am @@ -111,6 +111,7 @@ html_files = \ rsyslog_conf_templates.html \ rsyslog_conf_nomatch.html \ queues_analogy.html \ + multi_ruleset.html \ src/classes.dia grfx_files = \ diff --git a/doc/multi_ruleset.html b/doc/multi_ruleset.html new file mode 100644 index 00000000..532edbcf --- /dev/null +++ b/doc/multi_ruleset.html @@ -0,0 +1,198 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html><head> +<title>Multiple Rulesets in rsyslog</title></head> +<body> +<h1>Multiple Rulesets in rsyslog</h1> +<p>Starting with version 4.5.0 and 5.1.1, <a href="http://www.rsyslog.com">rsyslog</a> supports +multiple rulesets within a single configuration. +This is especially useful for routing the recpetion of remote messages to a set of specific rules. +Note that the input module must support binding to non-standard rulesets, so the functionality +may not be available with all inputs. +<p>In this document, I am using the <a href="imtcp.html">imtcp</a> in this text, an input module +that supports binding to non-standard rulesets as long as rsyslog supports multiple rulesets. +<h2>What is a Ruleset?</h2> +If you have worked with (r)syslog.conf, you know that it is made up of what I call rules (others +tend to call them selectors, an sysklogd term). Each rule consist of a filter and one or more +actions to be carried out when the filter evaluates to true. A filter may be a simple traditional +syslog priority based filter (like "*.*" or "mail.info" or a complex +script-like expression. Details on that are covered in the config file documentation. After the +filter come action specifiers, and an action is something that does something to a message, e.g. +write it to a file or forward it to a remote logging server. + +<p>A traditional configuration file is made up of one or more of these rules. When a new +message arrives, its processing starts with the first rule (in order of appearance in +rsyslog.conf) and continues for each rule until either all rules have been processed or +a so-called "e;discard" action happens, in which case processing stops and the +message is thrown away (what also happens after the last rule has been processed). + +<p>The <b>multi-ruleset</b> support now permits to specify more than one such rule sequence. +You can think of a traditional config file just as a single default rule set, which is +automatically bound to each of the inputs. This is even what actually happens. When +rsyslog.conf is processed, the config file parser looks for the directive + +<pre>$RuleSet <name> +</pre> + +<p>Where name is any name the user likes. If it finds this directive, it begins a new +rule set (if the name was not yet know) or switches to an already-existing one (if the name +was known). All rules defined between this $RuleSet directive and the next one are appended +to the named ruleset. Note that the reserved name "RSYSLOG_DefaultRuleset" is used to +specify rsyslogd's default ruleset. You can use that name whereever you can use a ruleset name, +including when binding an input to it. + +<p>Inside a ruleset, messages are processed as described above: they start with the first rule +and rules are processed in the order of appearance of the configuration file until either +there are no more rules or the discard action is executed. Note that with multiple rulesets +no longer <b>all</b> rsyslog.conf rules are executed but <b>only</b> those that are +contained within the specific ruleset. + +<p>Inputs must explicitely bind to rulesets. If they don't do, the default ruleset is used. + +This brings up the next question: + +<h2>What does "To bind to a Ruleset" mean?</h2> +<p>This term is used in the same sense as "to bind an IP address to an interface": +it means that a specific input, or part of an input (like a tcp listener) will use a specific +ruleset to "pass its messages to". So when a new message arrives, it will be processed +via the bound ruleset. Rule from all other rulesets are irrelevant and will never be processed. +<p>This makes multiple rulesets very handy to process local and remote message via +seperate means: bind the respective receivers to different rule sets, and you do not need +to seperate the messages by any other method. + +<p>Binding to rulesets is input-specifc. For imtcp, this is done via the + +<pre>$InputTCPServerBindRuleset <name> +</pre> + +directive. Note that "name"e; must be the name of a ruleset that is already defined +at the time the bind directive is given. There are many ways to make sure this happens, but +I personally think that it is best to define all rule sets at the top of rsyslog.conf and +define the input at the bottom. This kind of reverses its traditional recommended ordering, but +seems to be a really useful and straightforward ways of doing things. +<h2>Examples</h2> +<h3>Split local and remote logging</h3> +<p>Let's say you have a pretty standard system that logs its local messages to the usual +bunch of files that are specified in the default rsyslog.conf. As an example, your rsyslog.conf +might look like this: + +<pre> +# ... module loading ... +# The authpriv file has restricted access. +authpriv.* /var/log/secure +# Log all the mail messages in one place. +mail.* /var/log/maillog +# Log cron stuff +cron.* /var/log/cron +# Everybody gets emergency messages +*.emerg * +... more ... +</pre> + +<p>Now, you want to add receive messages from a remote system and log these to +a special file, but you do not want to have these messages written to the files +specified above. The traditional approach is to add a rule in front of all others that +filters on the message, processes it and then discards it: + +<pre> +# ... module loading ... +# process remote messages +:fromhost-ip, isequal, "192.0.2.1" /var/log/remotefile +& ~ +# only messages not from 192.0.21 make it past this point + +# The authpriv file has restricted access. +authpriv.* /var/log/secure +# Log all the mail messages in one place. +mail.* /var/log/maillog +# Log cron stuff +cron.* /var/log/cron +# Everybody gets emergency messages +*.emerg * +... more ... +</pre> + +<p>Note the tilde character, which is the discard action!. Also note that we assume that +192.0.2.1 is the sole remote sender (to keep it simple). + +<p>With multiple rulesets, we can simply define a dedicated ruleset for the remote reception +case and bind it to the receiver. This may be written as follows: + +<pre> +# ... module loading ... +# process remote messages +# define new ruleset and add rules to it: +$RuleSet remote +*.* /var/log/remotefile +# only messages not from 192.0.21 make it past this point + +# bind ruleset to tcp listener +$InputTCPServerBindRuleset remote +# and activate it: +$InputTCPServerRun 10514 + +# switch back to the default ruleset: +$RuleSet RSYSLOG_DefaultRuleset +# The authpriv file has restricted access. +authpriv.* /var/log/secure +# Log all the mail messages in one place. +mail.* /var/log/maillog +# Log cron stuff +cron.* /var/log/cron +# Everybody gets emergency messages +*.emerg * +... more ... +</pre> + +<p>Here, we need to switch back to the default ruleset after we have defined our custom +one. This is why I recommend a different ordering, which I find more intuitive. The sample +below has it, and it leads to the same results: + +<pre> +# ... module loading ... +# at first, this is a copy of the unmodified rsyslog.conf +# The authpriv file has restricted access. +authpriv.* /var/log/secure +# Log all the mail messages in one place. +mail.* /var/log/maillog +# Log cron stuff +cron.* /var/log/cron +# Everybody gets emergency messages +*.emerg * +... more ... +# end of the "regular" rsyslog.conf. Now come the new definitions: +# process remote messages +# define new ruleset and add rules to it: +$RuleSet remote +*.* /var/log/remotefile + +# bind ruleset to tcp listener +$InputTCPServerBindRuleset remote +# and activate it: +$InputTCPServerRun 10514 +</pre> + +<p>Here, we do not switch back to the default ruleset, because this is not needed as it is +completely defined. + +<p>Now look at the examples and compare them to the single-ruleset solution. You will notice +that we do <b>not</b> need a real filter in the multi-ruleset case: we can simply use +"*.*" as all messages now means all messages that are being processed by this +rule set and all of them come in via the TCP receiver! + +<h2>Performance</h2> +<p>No rule processing can be faster than not processing a rule at all. As such, it is useful +for a high performance system to identify disjunct actions and try to split these off to +different rule sets. In the example section, we had a case where three different tcp listeners +need to write to three different files. This is a perfect example of where multiple rule sets +are easier to use and offer more performance. The performance is better simply because there +is no need to check the reception service - instead messages are automatically pushed to the +right rule set and can be processed by very simple rules (maybe even with +"*.*"-filters, the fastest ones available). + +<p>[<a href="manual.html">manual index</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 © 2009 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 3 or higher.</font></p> +</body></html> |