root/src/modules/external.xml

<module>
  <name>external</name>
  <description><para>The external module performs checks via external processes like more traditional monitoring systems.  While this approach is far less efficient and does not scale well on a single system, it provides easier transition from existing monitoring systems.  Checks should exit normally with an exit status of 0 for success, 1 or 2 for failure and 3 for unknown.  Exiting with a status of 3 is highly discouraged.  The standard output is provided as the status of the check.</para></description>
  <loader>C</loader>
  <image>external.so</image>
  <moduleconfig>
    <parameter name="user"
               required="optional"
               allowed=".+">The user under which the external checks should be executed.</parameter>
    <parameter name="group"
               required="optional"
               allowed=".+">The group under which the external checks should be executed.</parameter>
  </moduleconfig>
  <checkconfig>
    <parameter name="command"
               required="required"
               allowed=".+">The path to the command to be executed.  This is the first argument to the execve system call.</parameter>
    <parameter name="arg0"
               required="optional"
               allowed=".+">The program name.  If not specified, it is derived from the command argument. Normal interpolation rules apply.</parameter>
    <parameter name="arg\d+"
               required="optional"
               allowed=".+">The arguments to the program.  The external module will start with arg1 and increment collecting arguments until argN is not found.  Normal interpolation rules apply.</parameter>
    <parameter name="env_\S+"
               required="optional"
               allowed=".+">These parameters allow the setting of environment variables for the command execution.  The text following env_ is the key and the parameter value is the value of the environment variable to be set via execve.</parameter>
    <parameter name="output_extract"
               required="optional"
               allowed=".+">This is a regular expression that is globally applied to the stdout of the command.  Each match is turned into a metric. It is a requirement to used named capturing in the regular expression where "key" is the named match of the metric name and "value" is the named match for the matric value.  A sample for extracting performance data from Nagios commands would be: <![CDATA[(?<key>\S+)=(?<value>[^;\s]+)(?=[;\s])]]></parameter>
  </checkconfig>
  <examples>
    <example>
      <title>Checking a service via the /path/to/check_foo command.</title>
      <para>The hypothetical check_foo command takes a target host with the -H parameter, runs a check and returns its health via exit code and stdout. We set the environment variable QUUX to the value BAZ.  The check is against host 10.10.2.2.</para>
      <programlisting><![CDATA[
      <noit>
        <modules>
          <module image="external" name="external"/>
        </modules>
        <checks>
          <check uuid="1e8edc38-0d88-11de-93ee-af2195eab5d5"
                 module="external" name="foo" target="10.10.2.2">
            <config>
              <command>/path/to/check_foo</command>
              <arg1>-H</arg1>
              <arg2>%[target]</arg2>
              <env_QUUX>BAZ</env_QUUX>
            </config>
          </check>
        </checks>
      </noit>
      ]]></programlisting>
    </example>
  </examples>
</module>