Exporting Metrics to Nagios via the collectd-nagios Utility¶

This document provides an example of exporting filter node metrics to the Nagios monitoring system (the Nagios Core edition is suggested; however, this document is suitable for any Nagios edition) using the collectd-nagios utility.

Example Workflow¶

The following deployment scheme is used in this document:

• The Wallarm filter node is deployed on a host accessible via the 10.0.30.5 IP address and the node.example.local fully qualified domain name.

• Nagios is installed on a separate host accessible via the 10.0.30.30 IP address.

• To execute commands on a remote host, the NRPE plugin is used. The plugin comprises

  • The nrpe service that is installed on the monitored host alongside the filter node. It listens on the 5666/TCP standard NRPE port.
  • The check_nrpe NRPE Nagios plugin that is installed on the Nagios host and allows Nagios to execute commands on the remote host where the nrpe service is installed.

• NRPE will be used to call the collectd_nagios utility that provides the collectd metrics in a Nagios‑compatible format.

Configuring Metrics Export to Nagios¶

To configure metrics export from the filter node to Nagios, follow these steps:

1. Configure NRPE to Communicate with the Nagios Host¶

To do this, on a filter node host:

1. Open the NRPE configuration file (default: /usr/local/nagios/etc/nrpe.cfg).

2. Add the IP address or fully qualified domain name of the Nagios server to the allowed_hosts directive in this file. For example, if the Nagios host uses the 10.0.30.30 IP address:

   allowed_hosts=127.0.0.1,10.0.30.30
   

3. Restart the NRPE service by executing the appropriate command:

   Ubuntu 14.04Other supported distributions

   sudo service nrpe restart
   

   sudo systemctl restart nrpe
   

2. Install the Nagios NRPE Plugin on the Nagios Host¶

To do this, on the Nagios host, take the following steps:

1. Download and unzip the source files for the NRPE plugin, and install the necessary utilities to build and install the plugin (see the NRPE documentation for details).

2. Go to the directory with the plugin source code, build from sources, then install the plugin.

   The minimal steps to take are:

   ./configure
   make all
   make install-plugin
   

3. Make Sure the NRPE Nagios Plugin Successfully Interacts with the NRPE Service¶

To do this, execute the following command on the Nagios host:

/usr/local/nagios/libexec/check_nrpe -H node.example.local

If NRPE is operating normally, the command’s output should contain an NRPE version (e.g., NRPE v3.2.1).

4. Define the check_nrpe Command to Run the NRPE Nagios Plugin with a Single Argument on the Nagios Host¶

To do this, add to the /usr/local/nagios/etc/objects/commands.cfg file the following lines:

define command{
    command_name check_nrpe
    command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
 }

5. Install the collectd_nagios Utility on the Filter Node Host¶

Execute one of the following commands:

sudo apt -y install --no-install-recommends collectd-utils

sudo yum install -y collectd-utils

6. Configure the collectd-nagios Utility to Run with Elevated Privileges on Behalf of the nagios User¶

To do this, perform the following steps on the filter node host:

1. Using the visudo utility, add the following line to the /etc/sudoers file:

   nagios ALL=(ALL:ALL) NOPASSWD:/usr/bin/collectd-nagios
   

   This allows the nagios user to run the collectd-nagios utility with superuser privileges using sudo without the need to provide any passwords.

   Running collectd-nagios with superuser privileges

   The utility must be run with superuser privileges because it uses the collectd Unix domain socket to receive data. Only a superuser can access this socket.

2. Make sure that the nagios user can receive metric values from collectd by executing the following test command:

   sudo -u nagios sudo /usr/bin/collectd-nagios -s /var/run/wallarm-collectd-unixsock -n wallarm_nginx/gauge-abnormal -H node.example.local
   

   This command allows the nagios user to get the value of the wallarm_nginx/gauge-abnormal metric (the number of processed requests) for the node.example.local host.

   Example of command output:

   OKAY: 0 critical, 0 warning, 1 okay | value=0.000000;;;;
   

3. Add a prefix to the NRPE service configuration file so that it will be able to execute commands using the sudo utility:

   command_prefix=/usr/bin/sudo
   

7. Add Commands to the NRPE Service Configuration File on the Filter Node to Get the Required Metrics¶

For example, to create a command named check_wallarm_nginx_abnormal that will receive the wallarm_nginx/gauge-abnormal metric for the filter node with the node.example.local fully qualified domain name, add the following line to the NRPE service’s configuration file:

command[check_wallarm_nginx_abnormal]=/usr/bin/collectd-nagios -s /var/run/wallarm-collectd-unixsock -n wallarm_nginx/gauge-abnormal -H node.example.local

After you have added all necessary commands to the NRPE service configuration file, restart the service by executing the appropriate command:

sudo service nrpe restart

sudo systemctl restart nrpe

8. On the Nagios Host, Use the Configuration Files to Specify the Filter Node Host and to Define the Services to Monitor¶

For example, this can be done as follows:

1. Create a /usr/local/nagios/etc/objects/nodes.cfg file with the following contents:

   define host{
    use linux-server
    host_name node.example.local
    address 10.0.30.5
   }
   
   define service {
     use generic-service
     host_name node.example.local
     check_command check_nrpe!check_wallarm_nginx_abnormal
     max_check_attempts 5
     service_description wallarm_nginx_abnormal
   }
   

   This file defines the node.example.local host with the 10.0.30.5 IP address and the command to check the status of the wallarm_nginx_abnormal service, which means receiving the wallarm_nginx/gauge-abnormal metric from the filter node (see the description of the check_wallarm_nginx_abnormal command).

2. Add the following line to the Nagios configuration file (by default, /usr/local/nagios/etc/nagios.cfg):

   cfg_file=/usr/local/nagios/etc/objects/nodes.cfg
   

   This is necessary for Nagios to start using the data from the nodes.cfg file on the next start.

3. Restart the Nagios service by running the appropriate command:

sudo service nagios restart

sudo systemctl restart nagios

Setup is Complete¶

Nagios is now monitoring the service associated with the specific metric of the filter node. If necessary, you can define other commands and services to check the metrics you are interested in.

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