add support for deleting older backups

roles/docker_s3_backup/defaults/main.yml

@@ -1,6 +1,9 @@
 ---
 # defaults file for chatton.docker_s3_backup
 
+# the number of backups of the same volume which should be kept.
+# Any excess will be deleted.
+docker_backup_retain_count: 3
 # the backup directory where backups are stored on the host machine.
 # these will be uploaded to S3.
 docker_backup_aws_s3_region: "us-east-1"

roles/docker_s3_backup/files/scripts/determine-s3-keys-to-delete.py

@@ -0,0 +1,21 @@
+#!/usr/bin/python
+import os
+
+
+def main():
+    s3_result = eval(os.getenv("S3_RESULTS"))
+    num_backups_to_keep = int(os.getenv("NUM_BACKUPS_TO_KEEP"))
+
+    items_to_delete = []
+    for res in s3_result:
+        s3_keys = res["s3_keys"]
+        # fetch all of the backups before the desired number.
+        # these are the ones we want to delete.
+        items_to_delete.extend(s3_keys[0:-num_backups_to_keep])
+
+    for item in items_to_delete:
+        print(item)
+
+
+if __name__ == "__main__":
+    main()

roles/docker_s3_backup/tasks/main.yml

@@ -55,3 +55,36 @@
     mode: put
     permission: "{{ docker_backup_aws_s3_permissions }}"
   with_items: "{{ volume_mounts }}"
+
+# try and find latest volume based on the name.
+- name: Fetch Volumes From S3.
+  amazon.aws.aws_s3:
+    bucket: "{{ docker_backup_aws_s3_bucket }}"
+    mode: list
+    prefix: "{{ item.Name }}/{{ item.Name }}"
+    aws_access_key: "{{ docker_backup_aws_s3_aws_access_key }}"
+    aws_secret_key: "{{ docker_backup_aws_s3_aws_secret_key }}"
+    region: "{{ docker_backup_aws_s3_region }}"
+    s3_url: "{{ docker_backup_aws_s3_url }}"
+  register: s3_list_outputs
+  with_items: "{{ volume_mounts }}"
+
+# TODO: do this in a more native way rather than a python script reading env vars.
+- name: Determine which backups should be deleted.
+  script: scripts/determine-s3-keys-to-delete.py
+  environment:
+    S3_RESULTS: "{{ s3_list_outputs.results }}"
+    NUM_BACKUPS_TO_KEEP: "{{ docker_backup_retain_count}}"
+  register: python_output
+  changed_when: false
+
+- name: Delete old backups.
+  amazon.aws.aws_s3:
+    bucket: "{{ docker_backup_aws_s3_bucket }}"
+    aws_access_key: "{{ docker_backup_aws_s3_aws_access_key }}"
+    aws_secret_key: "{{ docker_backup_aws_s3_aws_secret_key }}"
+    region: "{{ docker_backup_aws_s3_region }}"
+    s3_url: "{{ docker_backup_aws_s3_url }}"
+    object: "{{ item }}"
+    mode: delobj
+  with_items: "{{ python_output.stdout_lines }}"

tests/docker-compose.yml

@@ -8,9 +8,11 @@ services:
     - 9000:9000
     volumes:
     - portainer_data:/data
+    - some_volume:/some_dir
     - /var/run/docker.sock:/var/run/docker.sock
 
 volumes:
+  some_volume:
   portainer_data:
     external: true
     name: portainer_data