add loki role

roles/loki/defaults/main.yaml

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+---
+loki_go_arch_map:
+  i386: '386'
+  x86_64: 'amd64'
+
+loki_go_arch: "{{ loki_go_arch_map[ansible_architecture] | default('amd64') }}"
+
+loki_service_name: loki.service
+loki_service_enabled: true
+loki_service_state: started
+
+loki_version_regex: ^loki, version ([\d.]+)
+
+loki_github_project_url: https://github.com/grafana/loki
+loki_release_file: "loki-{{ ansible_system | lower }}-{{ loki_go_arch }}.zip"
+loki_release_url: "{{ loki_github_project_url }}/releases/download/v{{ loki_version }}/{{ loki_release_file }}"
+loki_checksum_url: "{{ loki_github_project_url }}/releases/download/v{{ loki_version }}/SHA256SUMS"
+loki_download_path: "/tmp/{{ loki_release_file }}"
+loki_unarchive_dest_path: /tmp
+loki_extracted_path: "{{ loki_download_path | replace('.zip', '') }}"
+
+loki_user: loki
+loki_user_state: present
+loki_user_shell: /usr/sbin/nologin
+
+loki_group: loki
+loki_group_state: "{{ loki_user_state | default('present') }}"
+
+loki_config_path: /etc/loki.yaml
+
+loki_var_path: /var/lib/loki
+loki_var_owner: "{{ loki_user }}"
+loki_var_group: "{{ loki_group }}"
+loki_var_mode: "0755"
+
+loki_bin_path: /usr/local/bin
+
+loki_auth_enabled: false
+
+loki_server:
+  http_listen_port: 3100
+
+loki_ingester:
+  lifecycler:
+    address: 127.0.0.1
+    ring:
+      kvstore:
+        store: inmemory
+      replication_factor: 1
+    final_sleep: 0s
+  chunk_idle_period: 5m
+  chunk_retain_period: 30s
+
+loki_schema_config:
+  configs:
+  - from: 2020-05-15
+    store: boltdb
+    object_store: filesystem
+    schema: v11
+    index:
+      prefix: index_
+      period: 168h
+
+loki_storage_config:
+  boltdb:
+    directory: "{{ loki_var_path }}/index"
+  filesystem:
+    directory: "{{ loki_var_path }}/chunks"
+
+loki_limits_config:
+  enforce_metric_name: false
+  reject_old_samples: true
+  reject_old_samples_max_age: 168h
+  ingestion_burst_size_mb: 16

roles/loki/handlers/main.yaml

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+---
+- name: restart loki
+  systemd:
+    name: loki.service
+    daemon_reload: true
+    state: restarted

roles/loki/tasks/configure.yaml

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+---
+- name: create group
+  group:
+    name: "{{ loki_group }}"
+    system: true
+    state: "{{ loki_group_state | default('present') }}"
+
+- name: create user
+  user:
+    name: "{{ loki_user }}"
+    system: true
+    shell: "{{ loki_user_shell }}"
+    group: "{{ loki_group }}"
+    createhome: false
+    home: "{{ loki_var_path }}"
+    state: "{{ loki_user_state | default('present') }}"
+
+- name: configure
+  template:
+    src: loki.yaml.j2
+    dest: "{{ loki_config_path }}"
+    owner: root
+    group: root
+    mode: 0444
+  notify: restart loki
+
+- name: create var path
+  file:
+    path: "{{ loki_var_path }}"
+    state: directory
+    owner: "{{ loki_var_owner }}"
+    group: "{{ loki_var_group }}"
+    mode: "{{ loki_var_mode }}"
+
+- name: configure systemd template
+  template:
+    src: "{{ loki_service_name }}.j2"
+    dest: "/etc/systemd/system/{{ loki_service_name }}"
+    owner: root
+    group: root
+    mode: 0444
+  notify: restart loki
+
+- name: manage service
+  service:
+    name: "{{ loki_service_name }}"
+    enabled: "{{ loki_service_enabled }}"
+    state: "{{ loki_service_state }}"

roles/loki/tasks/install.yaml

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+---
+- block:
+  - name: download archive
+    get_url:
+      url: "{{ loki_release_url }}"
+      dest: "{{ loki_download_path }}"
+      checksum: "{{ loki_checksum }}"
+    register: dl
+    until: dl is success
+    retries: 5
+    delay: 10
+
+  - name: extract archive
+    unarchive:
+      src: "{{ loki_download_path }}"
+      dest: "{{ loki_unarchive_dest_path }}"
+      creates: "{{ loki_extracted_path }}/loki"
+      remote_src: true
+
+  - name: install binaries
+    copy:
+      src: "{{ loki_extracted_path }}"
+      dest: "{{ loki_bin_path }}/loki"
+      owner: root
+      group: root
+      mode: 0755
+      remote_src: true
+    notify: restart loki
+  when: loki_version != loki_local_version

roles/loki/tasks/main.yaml

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+---
+- name: gather os specific variables
+  include_vars: "{{ lookup('first_found', possible_files) }}"
+  vars:
+    possible_files:
+      files:
+        - "{{ ansible_distribution }}-{{ ansible_distribution_version }}.yaml"
+        - "{{ ansible_distribution }}.yaml"
+        - "{{ ansible_os_family }}.yaml"
+        - "default.yaml"
+      paths:
+        - vars
+
+- name: include os specific tasks
+  include_tasks: "{{ lookup('first_found', possible_files) }}"
+  vars:
+    possible_files:
+      files:
+        - "{{ ansible_distribution }}-{{ ansible_distribution_version }}.yaml"
+        - "{{ ansible_distribution }}.yaml"
+        - "{{ ansible_os_family }}.yaml"
+        - "default.yaml"
+      paths:
+        - tasks
+
+- include: pre.yaml
+
+- include: install.yaml
+
+- include: configure.yaml

roles/loki/tasks/pre.yaml

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+---
+- name: determine if installed
+  stat:
+    path: "{{ loki_bin_path }}/loki"
+  register: st
+
+- name: set loki_installed
+  set_fact:
+    loki_installed: "{{ st.stat.exists | bool }}"
+
+- block:
+  - name: determine latest version
+    uri:
+      url: https://api.github.com/repos/grafana/loki/releases/latest
+      return_content: true
+      body_format: json
+    register: _latest_version
+    until: _latest_version.status == 200
+    retries: 3
+
+  - name: set loki_version
+    set_fact:
+      loki_version: "{{ _latest_version.json['tag_name'] | regex_replace('^v', '') }}"
+
+- block:
+  - name: determine installed version
+    command: "{{ loki_bin_path }}/loki --version"
+    register: _installed_version_string
+    changed_when: false
+
+  - name: set loki_local_version
+    set_fact:
+      loki_local_version: "{{ _installed_version_string.stdout | regex_search(loki_version_regex, '\\1') | first }}"
+  when: loki_installed
+
+- name: set loki_local_version to 0
+  set_fact:
+    loki_local_version: "0"
+  when: not loki_installed
+
+- block:
+  - name: get checksums
+    set_fact:
+      _checksums: "{{ lookup('url', loki_checksum_url, wantlist=True) }}"
+
+  - name: set loki_checksum
+    set_fact:
+      loki_checksum: "sha256:{{ item.split(' ') | first }}"
+    loop: "{{ _checksums }}"
+    when: "loki_release_file in item"

roles/loki/templates/loki.service.j2

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+{{ ansible_managed | comment }}
+
+[Unit]
+Description=Loki
+After=network-online.target
+
+[Service]
+Type=simple
+User={{ loki_user }}
+Group={{ loki_group }}
+ExecStart={{ loki_bin_path }}/loki \
+  -config.file {{ loki_config_path }}
+WorkingDirectory={{ loki_var_path }}
+
+Restart=always
+RestartSec=1
+
+[Install]
+WantedBy=multi-user.target

roles/loki/templates/loki.yaml.j2

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+{{ ansible_managed | comment }}
+---
+{% if loki_auth_enabled is defined %}
+auth_enabled: {{ loki_auth_enabled | bool | lower }}
+{% endif %}
+
+{% if loki_server is defined %}
+server:
+  {{ loki_server | to_nice_yaml(indent=2) | indent(2, False) }}
+{% endif -%}
+
+{% if loki_ingester is defined %}
+ingester:
+  {{ loki_ingester | to_nice_yaml(indent=2) | indent(2, False) }}
+{% endif -%}
+
+{% if loki_schema_config is defined %}
+schema_config:
+  {{ loki_schema_config | to_nice_yaml(indent=2) | indent(2, False) }}
+{% endif -%}
+
+{% if loki_storage_config is defined %}
+storage_config:
+  {{ loki_storage_config | to_nice_yaml(indent=2) | indent(2, False) }}
+{% endif -%}
+
+{% if loki_limits_config is defined %}
+limits_config:
+  {{ loki_limits_config | to_nice_yaml(indent=2) | indent(2, False) }}
+{% endif -%}