..
  This file is part of GNU TALER.
  Copyright (C) 2014-2023 Taler Systems SA

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU Affero General Public License as published by the Free Software
  Foundation; either version 2.1, or (at your option) any later version.

  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>

  @author Javier Sepulveda


Nginx Prometheus Exporter
#########################

.. contents:: Table of Contents
  :depth: 1
  :local:

Download nginx-prometheus-exporter
==================================

* Download
* Extract
* Copy to /usr/local/bin
* Set ownership and permissions

.. code-block:: console

   # mkdir -p /tmp/nginx_exporter_tmp && cd /tmp/nginx_exporter_tmp
   # wget https://github.com/nginxinc/nginx-prometheus-exporter/releases/download/v1.2.0/nginx-prometheus-exporter_1.2.0_linux_amd64.tar.gz
   # tar axf nginx-prometheus-exporter_1.2.0_linux_amd64.tar.gz
   # cd nginx-prometheus-exporter
   # cp nginx-prometheus-exporter /usr/local/bin


Create a system user
====================

.. code-block:: console

   # useradd --system --no-create-home --shell /bin/false nginx-exporter


Systemd configuration
=====================

Nginx-prometheus-exporter systemd service file
----------------------------------------------

.. code-block:: systemd

   # Path:/etc/systemd/system/nginx-exporter.service

   [Unit]
   Description=NGINX Prometheus Exporter
   Requires=nginx-exporter.socket

   [Service]
   User=nginx-exporter
   ExecStart=/usr/local/bin/nginx-prometheus-exporter --nginx.scrape-uri="http://127.0.0.1/metrics" --web.systemd-socket

   [Install]
   WantedBy=multi-user.target


Nginx-prometheus-exporter systemd socket file
---------------------------------------------

.. code-block:: systemd

   # Path: /etc/systemd/system/nginx-exporter.socket

   [Unit]
   Description=NGINX Prometheus Exporter

   [Socket]
   ListenStream=9113

   [Install]
   WantedBy=sockets.target

Modify the Prometheus configuration file
========================================

.. code-block:: yaml

   # Path: /etc/prometheus/prometheus.yml

   # Job, for nginx_exporter
     - job_name: 'nginx_exporter'
       static_configs:
         - targets: ['localhost:9113'] # choose port number


Nginx configuration
===================

.. code-block:: nginx

   server {
      listen localhost;
      root /var/www/html;
      index index.html;
      server_name _;

      location /metrics {
         stub_status on;
         access_log off;
         allow 127.0.0.1;
         deny all;
         }

     }


.. code-block:: console

   ## Create the Nginx symbolic link to enable the virtualhost file
   # ln -s /etc/nginx/sites-available/nginx-exporter.conf /etc/nginx/sites-enabled/nginx-exporter.conf
   # nginx -t
   # systemctl reload nginx
   ## Check with curl
   # curl http://localhost/metrics

Restart everything
==================

.. code-block:: console

   # systemctl daemon-reload # Only necessary if modified
   # systemctl enable --now node-exporter.service
   # systemctl status node-exporter.service
   # systemctl restart prometheus.service


Close the 9113 port with Nginx
==============================

* Change the nginx-exporter.socket file

.. code-block:: console

   # Path: /etc/systemd/system/nginx-exporter.socket

   [Unit]
   Description=NGINX Prometheus Exporter

   # Add here the loopback ip address
   [Socket]
   ListenStream=127.0.0.1:9113

   [Install]
   WantedBy=sockets.target


Add a new server block to Nginx
===============================

.. code-block:: nginx

   server {
    listen 80;
    listen [::]:80;

    server_name ip_address | subdomain.ltd;
        location /nginx-exporter {
          proxy_pass http://localhost:9113;
          }

   }

Create a new dashboard in Grafana
=================================

You can now go to the `Grafana dashboards <a href="https://grafana.taler.net/dashboards">`_ and easily
add the new dashboard for the Nginx Exporter program. Please make sure you choose the right Prometheus data source.

* Dashboard Id: 11199
* Dashboard URL: https://grafana.com/grafana/dashboards/11199-nginx/