Prometheus : Set Alert Notification (Email)2021/09/17

	This is the Alert Notification Settings on Prometheus. There are many way to receive Alerts like Slack, HipChat, WeChat and others, though, on this example, Configure Alerting with Email Receiver. For more details of Alerting, Refer to the official documents. ⇒ https://prometheus.io/docs/alerting/configuration/
[1]	For Email notification, it needs SMTP Server. On this example, it based on the environment that SMTP Server is running on localhost.
[2]	Install Alertmanager on Prometheus Server Host.

root@dlp:~#

apt -y install prometheus-alertmanager

[3]	Configure Prometheus Alert Settings with Email notification.

root@dlp:~#

mv /etc/prometheus/alertmanager.yml /etc/prometheus/alertmanager.yml.org

root@dlp:~#

vi /etc/prometheus/alertmanager.yml

# create new

global:
  # SMTP server to use
  smtp_smarthost: 'localhost:25'
  # require TLS or not
  smtp_require_tls: false
  # notification sender's Email address
  smtp_from: 'Alertmanager <root@dlp.srv.world>'
  # if set SMTP Auth on SMTP server, set below, too
  # smtp_auth_username: 'alertmanager'
  # smtp_auth_password: 'password'

route:
  # Receiver name for notification
  receiver: 'email-notice'
  # grouping definition
  group_by: ['alertname', 'Service', 'Stage', 'Role']
  group_wait:      30s
  group_interval:  5m
  repeat_interval: 4h

receivers:
# any name of Receiver
- name: 'email-notice'
  email_configs:
  # destination Email address
  - to: "root@localhost"

# configure Alerting rules

root@dlp:~#

vi /etc/prometheus/alert_rules.yml

# create new

# for example, monitor node-exporter's [Up/Down]

groups:
- name: Instances
  rules:
  - alert: InstanceDown
    expr: up == 0
    for: 5m
    labels:
      severity: critical
    annotations:
      description: '{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes.'
      summary: 'Instance {{ $labels.instance }} down'

root@dlp:~#

vi /etc/prometheus/prometheus.yml

# line 14 : confirm - (Alertmanager Host):(Port)
alerting:
  alertmanagers:
  - static_configs:
    - targets: ['localhost:9093']

# line 23 : add alert rules created above
rule_files:
  # - "first_rules.yml"
  # - "second_rules.yml"
  - "alert_rules.yml"

root@dlp:~#

systemctl restart prometheus prometheus-alertmanager

root@dlp:~#

systemctl enable prometheus-alertmanager

[4]	If [node-exporter] is down, following Email is sent. (mail body is HTML)

root@dlp:~#

mail

Return-Path: <root@dlp.srv.world>
X-Original-To: root@localhost
Delivered-To: root@localhost
Received: from localhost (localhost [IPv6:::1])
        by dlp.srv.world (Postfix) with ESMTP id E6B7AA2166
        for <root@localhost>; Thu, 16 Sep 2021 22:47:07 -0500 (CDT)
Subject: [FIRING:1] InstanceDown (node01.srv.world:9100 Hiroshima example critic
al)
To: root@localhost
From: Alertmanager <root@dlp.srv.world>
Message-Id: <1631850427945847646.13718895160637918488@dlp.srv.world>
Date: Thu, 16 Sep 2021 22:47:07 -0500
Content-Type: multipart/alternative;  boundary=50fcf05622e22fc2a3dd0a59dbdcefd36
5940b2cfc18f77d141da42ca370
MIME-Version: 1.0

--50fcf05622e22fc2a3dd0a59dbdcefd365940b2cfc18f77d141da42ca370
Content-Transfer-Encoding: quoted-printable
Content-Type: text/html; charset=UTF-8
.....
.....

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