..
  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


Grafana Loki
############

Loki is an aggregation system really similar to Prometheus, but instead of reading metrics, it reads logs (via push).
Please check the `official documentation website <https://grafana.com/docs/loki/latest/get-started/>`_ for additional information. 
 

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

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

.. code-block:: console

   # useradd --system --no-create-home --shell /bin/false loki
   # useradd --system --no-create-home --shell /bin/false promtail

Download Loki
=============

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

.. code-block:: console

   # cd /tmp
   # wget https://github.com/grafana/loki/releases/download/v3.0.0/loki-linux-amd64.zip
   # unzip loki-linux-amd64.zip -d .
   # mv loki-linux-amd64 loki
   # cp loki /usr/local/bin/

Loki configuration file
=========================================

.. code-block:: yaml

   auth_enabled: false

   server:
     http_listen_port: 3100
     grpc_listen_port: 9096

   common:
     instance_addr: 127.0.0.1
     path_prefix: /tmp/loki
     storage:
       filesystem:
          chunks_directory: /tmp/loki/chunks
          rules_directory: /tmp/loki/rules
     replication_factor: 1
     ring:
       kvstore:
         store: inmemory

   query_range:
     results_cache:
       cache:
         embedded_cache:
           enabled: true
           max_size_mb: 100

   schema_config:
     configs:
       - from: 2020-10-24
         store: tsdb
         object_store: filesystem
         schema: v13
         index:
           prefix: index_
           period: 24h

Systemd service file
====================

.. code-block:: systemd

   # Path: /etc/systemd/system/loki.service

   [Unit]
   Description=Loki service
   After=network.target

   [Service]
   Type=simple
   User=loki
   ExecStart=/usr/local/bin/loki -config.file /etc/loki/config.yml
   # Give a reasonable amount of time for the server to start up/shut down
   TimeoutSec = 120
   Restart = on-failure
   RestartSec = 2

   [Install]
   WantedBy=multi-user.target

Refresh systemd and restart
===========================

.. code-block:: console

   # systemctl daemon-reload
   # systemctl enable --now loki
   # systemctl status loki
   # systemctl restart prometheus

Check
-----

http://ip:3100

Close the 3100 port with Nginx
==============================

.. code-block:: nginx

   # Path: /etc/nginx/sites-available/loki.conf

   upstream loki {
    server 127.0.0.1:3100; # Loopback
    keepalive 15;
   }

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

   server_name loki.taler-ops.ch;
   root /dev/null;

   # LOKI

   location / {
    proxy_read_timeout 1800s;
    proxy_connect_timeout 1600s;
    proxy_pass http://loki;
    }

   location /ready {
    proxy_pass http://loki;
    proxy_http_version 1.1;
    proxy_set_header Connection "Keep-Alive";
    proxy_set_header Proxy-Connection "Keep-Alive";
    proxy_redirect off;
    auth_basic "off";
    }

   }

- Enable in Nginx the new virtualhost file

.. code-block:: console

   # ln -s /etc/nginx/sites-available/loki.conf /etc/nginx/sites-enabled/loki.conf
   # nginx -t
   # systemctl reload nginx

Edit the loki configuration file
================================

.. code-block:: yaml

  #Path: /etc/loki/config.yml
  server:
    http_listen_port: 3100
    grpc_listen_port: 9096
    # Add this to close the 3100 port
    http_listen_address: 127.0.0.1

Refresh systemd and restart
===========================

.. code-block:: console

   # systemctl restart nginx 
   # systemctl restart loki
   # systemctl restart prometheus

Check
-----

Check that the 3100 port is publicly closed by typing in your Web browser http://ip:3100. At
the same time change through the Grafana control panel, your loki data source server URL field,
so it can connect now through the specified subdomain in the nginx virtualhost file (in our test case
loki.taler-ops.ch). 

Grafana control panel
=====================

You can now to go the `Grafana control panel <https://grafana.taler.net>`_ and easily
add the new Loki data source.