alertmanager-fe.yaml

# This is the bullshit we have to do, because:
# 1. alertmanager upstream insists on embedding their assets inside the binary
#    this is against Debian Policy, so Debian has to patch it out downstream, but
# 2. there's no elm-compiler package in Debian
#    so Debian can't build script.js from source
#
# instead Debian provides a horrible generate-ui.sh script that downloads binary elm compiler
# from github and runs it as root without any hash verification or anything
#
# This means that neither Debian nor upsteram provide a prebuilt JS in a sane format.
# Fortunately upstream commits their generated golang source with embedded vfs into git
# which is silly but in this case it helps

- name: Install frontend dependencies
  become: "{{ not ansible_check_mode }}"
  ansible.builtin.package:
    state: present
    name:
      - libjs-bootstrap4
      - fonts-font-awesome
      - golang-github-prometheus-alertmanager-dev

- name: Detect alertmanager version
  check_mode: false
  changed_when: false
  ansible.builtin.shell:
    cmd: "dpkg-query -W prometheus-alertmanager |cut -f2 |cut -d+ -f1"
  register: prometheus_result_alertmanager_version

- ansible.builtin.set_fact:
    prometheus_alertmanager_installed_version: "{{ prometheus_result_alertmanager_version.stdout_lines[0] }}"

- name: Create a directory for alertmanager frontend bullshit
  ansible.builtin.file:
    state: directory
    path: "{{ prometheus_alertmanager_frontend_extract_dir }}/{{ prometheus_alertmanager_installed_version }}"

- name: Copy generated golang source with embedded alertmanager assets
  ansible.builtin.copy:
    remote_src: true
    unsafe_writes: "{{ ansible_check_mode }}" # broken unprivileged check mode otherwise
    src: /usr/share/gocode/src/github.com/prometheus/alertmanager/asset/assets_vfsdata.go
    dest: "{{ prometheus_alertmanager_frontend_extract_dir }}/{{ prometheus_alertmanager_installed_version }}/assets_vfsdata.go"

- name: Extract compressed hexstring from the generated source
  check_mode: false
  changed_when: false
  ansible.builtin.shell:
    chdir: "{{ prometheus_alertmanager_frontend_extract_dir }}/{{ prometheus_alertmanager_installed_version }}"
    cmd: >
      awk '
      /static\/{{ item }}.*vfsgen۰CompressedFileInfo/{S=1}
      (S==1 && /compressedContent/){print; S=0}
      ' assets_vfsdata.go
      |cut -d'"' -f2 |tr -d '\\x' >"{{ item }}.gz.hex"
  loop:
    - script.js

- name: Dehexify and decompress the extracted files
  check_mode: false
  changed_when: false
  ansible.builtin.shell:
    chdir: "{{ prometheus_alertmanager_frontend_extract_dir }}/{{ prometheus_alertmanager_installed_version }}"
    cmd: >
      xxd -r -p "{{ item }}.gz.hex" |zcat >"{{ item }}"
  loop:
    - script.js

- name: Prepare alertmanager asset dir (mkdirs)
  become: "{{ not ansible_check_mode }}"
  ansible.builtin.file:
    state: directory
    path: "{{ prometheus_alertmanager_frontend_dest_dir }}{{ item }}"
  loop:
    - ""
    - "/lib"

- name: Prepare alertmanager asset dir (symlinks)
  become: "{{ not ansible_check_mode }}"
  ansible.builtin.file:
    state: link
    src: "{{ item.value }}"
    path: "{{ prometheus_alertmanager_frontend_dest_dir }}/{{ item.key }}"
  loop: "{{ links |dict2items }}"
  vars:
    links:
      lib/font-awesome: /usr/share/fonts-font-awesome
      lib/font-awesome-4.7.0: /usr/share/fonts-font-awesome
      lib/bootstrap4: /usr/share/nodejs/bootstrap/dist
      lib/bootstrap-4.0.0-alpha.6-dist: /usr/share/nodejs/bootstrap/dist

- name: Prepare alertmanager asset dir (copies)
  become: "{{ not ansible_check_mode }}"
  ansible.builtin.copy:
    remote_src: true
    unsafe_writes: "{{ ansible_check_mode }}" # broken unprivileged check mode otherwise
    src: "{{ item.value }}"
    dest: "{{ prometheus_alertmanager_frontend_dest_dir }}/{{ item.key }}"
  loop: "{{ files |dict2items }}"
  vars:
    files:
      index.html: /usr/share/gocode/src/github.com/prometheus/alertmanager/ui/app/index.html
      favicon.ico: /usr/share/gocode/src/github.com/prometheus/alertmanager/ui/app/favicon.ico
      script.js: "{{ prometheus_alertmanager_frontend_extract_dir }}/{{ prometheus_alertmanager_installed_version }}/script.js"

- name: Configure alertmanager args
  become: "{{ not ansible_check_mode }}"
  ansible.builtin.lineinfile:
    path: /etc/default/prometheus-alertmanager
    regex: "^ARGS=.*"
    line: "ARGS=\"--web.ui-path={{ prometheus_alertmanager_frontend_dest_dir }}"
  notify: prometheus-restart-alertmanager