switch to using systemd service and timer instead of cron

Signed-off-by: Jakub Sokołowski <jakub@status.im>

README.md

@@ -34,3 +34,27 @@ If you want to use S3 you can set:
 ```yaml
 backup_base_domain: s3.amazonaws.com
 ```
+
+# Administration
+
+The upload job runs as a systemd service triggered by a timer.
+Assuming our backup target is called `database` you can do:
+```
+ $ sudo systemctl status backup-database.service
+● backup-database.service - "Service for uploading database backups to s3 buckets."
+   Loaded: loaded (/lib/systemd/system/backup-database.service; static; vendor preset: enabled)
+   Active: inactive (dead) since Fri 2020-01-24 15:08:57 UTC; 7min ago
+     Docs: https://github.com/status-im/infra-role-s3cmd-backup
+  Process: 15536 ExecStart=/var/lib/backups/backup_hackmd.sh (code=exited, status=0/SUCCESS)
+ Main PID: 15536 (code=exited, status=0/SUCCESS)
+
+Jan 24 15:08:44 node-01.do-ams3.todo.misc systemd[1]: Starting "Service for uploading database backups to s3 buckets."...
+Jan 24 15:08:44 node-01.do-ams3.todo.misc backup_database.sh[15536]: Uploading: database_db_dump_20200124040001.sql >> s3://hackmd-backups
+...
+```
+You can check the timer status too:
+```
+ $ sudo systemctl list-timers backup-database.timer
+NEXT                         LEFT    LAST PASSED UNIT                  ACTIVATES
+Sat 2020-01-25 00:00:00 UTC  8h left n/a  n/a    backup-database.timer backup-database.service
+```

defaults/main.yml

@@ -1,24 +1,28 @@
 ---
-# For uploading backups
+# tool for uploading to s3 compatible backends
 s3cmd_version: '2.0.2'
 s3cmd_name: 's3cmd-{{ s3cmd_version }}'
 s3cmd_archive: '{{ s3cmd_name }}.tar.gz'
 s3cmd_checksum: 'md5:7e4043186f46a6832ba3fb4d9cb59bb8'
 s3cmd_url: 'https://github.com/s3tools/s3cmd/releases/download/v{{ s3cmd_version }}/{{ s3cmd_archive }}'
 
-# Backup timing
-backup_hour: 2
-backup_minute: 0
-backup_day: '*'
-backup_month: '*'
+backup_name: 'default'
+backup_directory: ~
+backup_script_dir: '/var/lib/backups'
+backup_script: '{{ backup_script_dir }}/backup_{{ backup_name }}.sh'
+backup_service_path: '/lib/systemd/system'
+backup_service_name: 'backup-{{ backup_name }}'
+backup_service_user: root
+# It takes a bit to upload files
+backup_service_start_timeout: 120
+# Optionally wait for specified service to run
+backup_service_extra_after: ~
+# Backup frequency in systemd OnCalendar format
+backup_timer_frequency: 'daily'
 # Number of most recent files to backup
 backup_number: 1
 
 # Digital Ocean Spaces configuration
-backup_name: 'default'
-backup_directory: ~
-backup_script: '/var/lib/backups/backup_{{ backup_name }}.sh'
-#backup_base_domain: s3.amazonaws.com
 backup_base_domain: ams3.digitaloceanspaces.com
 # example: s3://discourse-backups
 backup_bucket_name: ~

tasks/backups.yml

@@ -1,27 +0,0 @@
----
-- name: Create directory for backup script
-  file:
-    path: '{{ item }}'
-    state: directory
-    group: adm
-    mode: 0775
-  with_items:
-    - /var/tmp/backups
-    - /var/lib/backups
-
-- name: Create backup script
-  template:
-    src: backup.sh
-    dest: '{{ backup_script }}'
-    mode: 0755
-
-- name: Configure a cron job for backups
-  cron:
-    name: Upload Discourse Backups
-    # backup happens at 03:30 UTC
-    hour:   '{{ backup_hour }}'
-    minute: '{{ backup_minute }}'
-    day:    '{{ backup_day }}'
-    month:  '{{ backup_month }}'
-    job:    '{{ backup_script }}'
-    user:   root

tasks/main.yml

@@ -1,3 +1,4 @@
 ---
 - include_tasks: s3cmd.yml
-- include_tasks: backups.yml
+- include_tasks: script.yml
+- include_tasks: timer.yml

tasks/script.yml

@@ -0,0 +1,16 @@
+---
+- name: Create directory for backup script
+  file:
+    path: '{{ item }}'
+    state: directory
+    group: adm
+    mode: 0775
+  with_items:
+    - '{{ backup_script_dir }}'
+    - '{{ backup_directory }}'
+
+- name: Create backup script
+  template:
+    src: backup.sh
+    dest: '{{ backup_script }}'
+    mode: 0755

tasks/timer.yml

@@ -0,0 +1,27 @@
+---
+- name: 'Create systemd service file: {{ backup_service_name }}'
+  template:
+    src: backup.service.j2
+    dest: '{{ backup_service_path }}/{{ backup_service_name }}.service'
+    mode: 0644
+
+- name: 'Create systemd timer file: {{ backup_service_name }}'
+  template:
+    src: backup.timer.j2
+    dest: '{{ backup_service_path }}/{{ backup_service_name }}.timer'
+    mode: 0644
+
+- name: Reload systemctl
+  command: systemctl daemon-reload
+
+- name: '(Re)start fetching service: {{ backup_service_name }}'
+  service:
+    name: '{{ backup_service_name }}.service'
+    state: started
+    enabled: true
+
+- name: 'Enable the service timer: {{ backup_service_name }}'
+  systemd:
+    name: '{{ backup_service_name }}.timer'
+    state: started
+    enabled: yes

templates/backup.service.j2

@@ -0,0 +1,14 @@
+[Unit]
+Description="Service for uploading {{ backup_name }} backups to s3 buckets."
+Documentation=https://github.com/status-im/infra-role-s3cmd-backup
+Requires=network-online.target
+After=network-online.target
+{% if backup_service_extra_after is defined %}
+After={{ backup_service_extra_after }}
+{% endif %}
+
+[Service]
+User={{ backup_service_user }}
+ExecStart={{ backup_script }}
+Type=oneshot
+TimeoutStartSec={{ backup_service_start_timeout }}

templates/backup.timer.j2

@@ -0,0 +1,6 @@
+[Unit]
+After=multi-user.target
+
+[Timer]
+OnCalendar={{ backup_timer_frequency }}
+Persistent=yes