Telegram notifier ignores HTML tags

[ntk148v]

What did you do?
Setup Prometheus and Alertmanager to send message to Telegram. Message is sent as raw text, no HTML tags are parsed.

What did you expect to see?

Message is formatted.

What did you see instead? Under which circumstances?

Environment

• System information:

• Alertmanager version:

Alertmanager image tag 'main':

docker pull quay.io/prometheus/alertmanager@sha256:1e5f1f22c0875ebffad1c39ffb5f831c94ba6dcf0be4d5e5d910cfaade11b1b7

• Prometheus version:

• Alertmanager configuration file:

route:
  group_wait: 5s
  group_interval: 30s
  receiver: 'telegram'

templates:
  - iaas-alertmanager.tmpl

receivers:
  - name: 'telegram'
    telegram_configs:
      - bot_token: 'xxxx'
        chat_id: -xxxx
        message: '{{ template "telegram.iaas.message" . }}'
        parse_mode: 'HTML'

iaas-alertmanager.tmpl file (simple notification template with HTML tags)

{{ define "__iaas_alert_list" }}
{{ range . }}
---
🪪 <b>{{ .Labels.alertname }}</b>
<b></b>
{{- if .Annotations.summary }}
📝 Summary: {{ .Annotations.summary }}{{ end }}{{- if .Annotations.title }}
📕 Title: {{ .Annotations.title }}{{ end }}{{- if .Annotations.description }}
📖 Description:
<code>{{ .Annotations.description }}</code>{{ end }}{{ if .Annotations.assignees }}
🏷️ Labels:{{ if .Labels.severity }}
    <i>Instance</i>: <code>{{ .Labels.instance  }}</code>{{ end }}{{ if .Labels.job }}
    <i>Job</i>: <code>{{ .Labels.job }}</code>{{ end }}
Owner: <code>Iaas team</code>
Since: <code>{{ .StartsAt.Local.Format "02/01/2006 15:04:05"  }}</code>
{{ if not .EndsAt.IsZero }}
Ended: <code>{{ .EndsAt.Local.Format "02/01/2006 15:04:05" }}</code>{{ end }}
{{ end }}
{{ end }}


{{ define "telegram.iaas.message" }}
{{- if gt (len .Alerts.Firing) 0 }}
🔥 Alerts Firing 🔥
{{- template "__iaas_alert_list" .Alerts.Firing }}
{{- end }}
{{- if gt (len .Alerts.Resolved) 0 }}
✅ Alerts Resolved ✅
{{- template "__iaas_alert_list" .Alerts.Resolved }}
{{- end }}
{{- end }}

{{ define "telegram.iaas.message.summary" }}
{{if eq .Status "firing"}}
<b>📑 {{.CommonAnnotations.summary}}</b>
{{ (index .Alerts 0).StartsAt.Local.Format "02/01/2006 15:04:05" }}
<b></b>
{{- range $val := .Alerts }}
{{ $val.Labels.alertname }}
{{ $val.Annotations.description }}
{{- end }}
{{ end }}
{{ end }}

• Prometheus configuration file:

global:
  scrape_interval: 1s
  evaluation_interval: 1s

rule_files:
  - 'rules.yml'

# alert
alerting:
  alertmanagers:
    - scheme: http
      static_configs:
        - targets:
            - 'localhost:9093'

scrape_configs:
  - job_name: prometheus
    metrics_path: /metrics/
    authorization:
      credentials: my_random_prometheus_secret
    static_configs:
      - targets: ['host.docker.internal:8080']

• Logs:

nothing special