matrix-bot-go-neb: alertmanager message template configuration incorrectly handled by ansible

Hey there,

I tried to deploy the matrix go-neb bot with alertmanager configuration today using the instructions at docs/configuring-playbook-bot-go-neb.md.

Expected behaviour

The go-neb bot is completely installed and able to communicate with an alertmanager instance.

Actual behaviour

During the first run, everything seemed to work fine, but I had some configuration errors. When I attempted to redeploy the service, ansible returned the following error:

fatal: [matrix.example.com]: FAILED! => 
  msg: |-
    The conditional check 'matrix_bot_go_neb_services is not defined or matrix_bot_go_neb_services[0] is not defined' failed. The error was: An unhandled exception occurred while templating '[{'ID': 'alertmanager_service', 'Type': 'alertmanager', 'UserID': '@alertmanager-goneb-bot:{{ matrix_domain }}', 'Config': {'webhook_url': 'https://goneb.example.com/services/hooks/YWxlcnRtYW5hZ2VyX3NlcnZpY2U', 'rooms': {'!roomID:example.com': {'text_template': '{{range .Alerts -}} [{{ .Status }}] {{index .Labels "alertname" }}: {{index .Annotations "description"}} {{ end -}}', 'html_template': '{{range .Alerts -}}  {{ $severity := index .Labels "severity" }}    {{ if eq .Status "firing" }}      {{ if eq $severity "critical"}}        <font color=\'red\'><b>[FIRING - CRITICAL]</b></font>      {{ else if eq $severity "warning"}}        <font color=\'orange\'><b>[FIRING - WARNING]</b></font>      {{ else }}        <b>[FIRING - {{ $severity }}]</b>      {{ end }}    {{ else }}      <font color=\'green\'><b>[RESOLVED]</b></font>    {{ end }}  {{ index .Labels "alertname"}} : {{ index .Annotations "description"}}   <a href="{{ .GeneratorURL }}">source</a><br/>{{end -}}', 'msg_type': 'm.text'}}}}]'. Error was a <class 'ansible.errors.AnsibleError'>, original message: template error while templating string: unexpected '.'. String: {{range .Alerts -}} [{{ .Status }}] {{index .Labels "alertname" }}: {{index .Annotations "description"}} {{ end -}}

    The error appears to be in './matrix-docker-ansible-deploy/roles/matrix-bot-go-neb/tasks/validate_config.yml': line 9, column 3, but may
    be elsewhere in the file depending on the exact syntax problem.

    The offending line appears to be:

    - name: Fail if there's not at least 1 service
      ^ here

Problem

Ansible appears to attempt to template the go template string in the alertmanager configuration.

Mitigation

I managed to mitigate the issue by escaping all of the curly brackets in the template in matrix.example.com/vars.yml. A better solution should be using jinja's {% raw %} expression syntax wrapped around the entire template string, but I could not get it to work in this case.

The relevant section in the README begins at line 201.

matrix_bot_go_neb_services:
  - ID: "alertmanager_service"
    Type: "alertmanager"
    UserID: "@alertmanager-goneb-bot:{{ matrix_domain }}"
    Config:
      # This is for information purposes only. It should point to Go-NEB path as follows:
      # `/services/hooks/<base64 encoded service ID>`
      # Where in this case "service ID" is "alertmanager_service"
      # Make sure your BASE_URL can be accessed by the Alertmanager instance!
      webhook_url: "https://goneb.example.com/services/hooks/YWxlcnRtYW5hZ2VyX3NlcnZpY2U"
      # Each room will get the notification with the alert rendered with the given template
      rooms:
        "!roomID.example.com":
          text_template: "{{ '{{' }}range .Alerts -{{ '}}' }} [{{ '{{' }} .Status {{ '}}' }}] {{  '{{' }}index .Labels \"alertname\" {{' }}'}}: {{ '{{' }}index .Annotations \"description\" {{ '}}' }} {{ '{{' }} end -{{ '}}' }}"
          html_template: "{{ '{{' }}range .Alerts -{{  '}}' }}  {{ '{{' }} $severity := index .Labels \"severity\" {{ '}}' }}    {{ '{{' }} if eq .Status \"firing\" {{ '}}' }}      {{ '{{' }} if eq $severity \"critical\"{{ '}}' }}        <font color='red'><b>[FIRING - CRITICAL]</b></font>      {{ '{{' }} else if eq $severity \"warning\"{{ '}}' }}        <font color='orange'><b>[FIRING - WARNING]</b></font>      {{ '{{' }} else {{ '}}' }}        <b>[FIRING - {{ '{{' }} $severity {{ '}}' }}]</b>      {{ '{{' }} end {{ '}}' }}    {{ '{{' }} else {{ '}}' }}      <font color='green'><b>[RESOLVED]</b></font>    {{ '{{' }} end {{ '}}' }}  {{ '{{' }} index .Labels \"alertname\"{{ '}}' }} : {{ '{{' }} index .Annotations \"description\"{{ '}}' }}   <a href=\"{{ '{{' }}.GeneratorURL {{ '}}' }}\">source</a><br/>{{ '{{' }}end -{{ '}}' }}"

I'm wondering if this was a mistake on my side during the execution of the ansible-playbook or if this is something that should be added to the documentation to help people in the future.

Steps to reproduce

Deploy matrix and element using the playbook and instructions in this repo
Deploy the go-neb-bot using the playbook and instructions in this repo
[ Potentially run playbook again. The issue did not occur during the first run. ]
Since the error occurs before any connection to alertmanager is established, it should not be required to deploy an alertmanager instance.

Environment

$ ansible-playbook --version
ansible-playbook [core 2.11.6] 
  [...]
  python version = 3.8.6 (v3.8.6:db455296be, Sep 23 2020, 13:31:39) [Clang 6.0 (clang-600.0.57)]
  jinja version = 2.11.3
  libyaml = True

$ uname -a
Darwin MacBook-Pro.local 19.6.0 Darwin Kernel Version 19.6.0: Sun Nov 14 19:58:51 PST 2021; root:xnu-6153.141.50~1/RELEASE_X86_64 x86_64

spantaleev / matrix-docker-ansible-deploy