Nginx Server

Overview

Nginx is an open-source Web Server also used as a proxy server for email (IMAP, POP3, and SMTP) and a reverse proxy and load balancer for HTTP, TCP, and UDP servers.

Monitoring Connector assets

Monitored objects

• Nginx Server

Collected metrics

Requests

Metric name	Description	Unit
server.connections.accepted.persecond	Number of accepted connections	Connections/second
server.connections.handled.persecond	Number of handled connections	Connections/second
server.connections.dropped.count	Number of dropped connections	Count
server.requests.persecond	Number of requests	Requests/second

Connections

Metric name	Description	Unit
server.connections.active.count	The number of active connections	Count
server.connections.waiting.count	The number of waiting connections	Count
server.connections.writing.count	The number of writing connections	Count
server.connections.reading.count	The number of reading connections	Count

Prerequisites

Warning: The following procedure is an example. Cannot be applied on all context.

The module allows the generation of a live Nginx report, available on a dedicated web page. This report is used to generate statistics in Centreon. To activate this module, you have to open your nginx configuration file:

$ vi /etc/nginx/nginx.conf

and check that if not already configured, add the followings lines in 'server' bracket:

server { 
    ... 
    location /nginx_status { 
        stub_status on; 
        access_log off;
        allow <centreon-poller_@IP>;
        deny all; 
    }
    ...
}

Make sure you are allowing Pollers to access this URL.

You can check the validity of your configuration using:

$ nginx -t nginx: the configuration file
/etc/nginx/nginx.conf syntax is ok nginx: configuration file
/etc/nginx/nginx.conf test is successful

Nginx must be reloaded to take this modification into account:

$ /etc/init.d/nginx reload

You can now check the result by accessing the URL

http://<nginx_address>/nginx_status

Installation

Online License

1. Install the Centreon package on every Centreon Poller expected to monitor Nginx Servers:

yum install centreon-plugin-Applications-Webservers-Nginx-Serverstatus

2. On the Centreon Web interface, install the Nginx Server Monitoring Connector through Configuration > Monitoring Connector Manager page.

Offline License

1. Install the Centreon package on every Centreon Poller expected to monitor Nginx Servers:

yum install centreon-plugin-Applications-Webservers-Nginx-Serverstatus

2. Install the Centreon Monitoring Connector RPM on the Centreon Central server:

yum install centreon-pack-applications-webservers-nginx-serverstatus

3. On the Centreon Web interface, install the Nginx Server Monitoring Connector through Configuration > Monitoring Connector Manager page.

Host configuration

• Log into Centreon and add a new Host through "Configuration > Hosts".
• Apply the App-Webserver-Nginx-ServerStatus-custom template and configure all the mandatory Macros :

Mandatory	Name	Description
X	NGINXPORT	Port used by Apache. Default is 80
X	NGINXPROTOCOL	Protocol used. Default is http
	NGINXSTATUSEXTRAOPTIONS	Any extra option you may want to add to the command (eg. a --verbose flag)

By default NGINXSTATUSEXTRAOPTIONS contains : --http-backend=curl --curl-opt="CURLOPT_SSL_VERIFYPEER => 0" options to use the curl backend and to ignore the validity's check of the SSL certificate.

How to test my Plugin and what do the main parameters stand for ?

Once the Plugin is installed, you can test it logging into the CLI with the centreon-engine user.

/usr/lib/centreon/plugins//centreon_nginx_serverstatus.pl \
    --plugin=apps::nginx::serverstatus::plugin \
    --mode=requests \
    --hostname=10.30.2.11 \
    --proto=https \
    --port=443 \
    --warning-connections-dropped=10 \
    --critical-connections-dropped=20 \
    --http-backend=curl \
    --curl-opt="CURLOPT_SSL_VERIFYPEER => 0" \
    --verbose   

The above command checks requests statistics on the Nginx server (--mode=requests). Mandatory options are the IP/FQDN of the device

(--hostname=10.30.2.11), the port used by Apache (--port=443) and the protocol (--proto=https).

The curl backend is used (--http-backend='curl') and the SSL certificate validity is not checked (--curl-opt="CURLOPT_SSL_VERIFYPEER => 0").

This command would trigger a WARNING alarm if the number of dropped connections on the server is greater than 10 (--warning-connections-dropped=10) and

a CRITICAL alarm if the number of dropped connections on the server is greater than 20 (--critical-connections-dropped=20).

Expected command output is shown below:

OK: connections accepted: 0.36/s - connections handled: 0.36/s - connections dropped: 0 - requests: 13.00/s | 'server.connections.accepted.persecond'=0.36;;;0; 'server.connections.handled.persecond'=0.36;;;0; 'server.connections.dropped.count'=0;0:0;0:20;0; 'server.requests.persecond'=13.00;;;0;

Some thresholds can also be set on metrics with options --warning-* and --critical-*.

All available options for a given mode can be displayed by adding the --help parameter to the command:

/usr/lib/centreon/plugins//centreon_nginx_serverstatus.pl \
    --plugin=apps::nginx::serverstatus::plugin \
    --mode=requests \
    --help

All Plugin modes can be listed with the following command:

usr/lib/centreon/plugins//centreon_nginx_serverstatus.pl \
    --plugin=apps::nginx::serverstatus::plugin \
    --list-mode 

Troubleshooting

UNKNOWN: Cannot load module 'Net::Curl::Easy'

This error message means that a Perl library required to use the curl backend is missing.

In order to fix this issue, install the Net::Curl::Easy Perl library using the following command:

yum install perl-Net-Curl

UNKNOWN: curl perform error : Couldn't connect to server

This error message means that the Centreon Plugin couldn't successfully connect to the URL of the Nginx Server. Check that no third party device (such as a firewall) is blocking the request. A proxy connection may also be necessary to connect to the server. This can be done by using the --proxyurl option in the command.