Automatically prune the inventory backup

The inventory backup process takes the running inventory json file and
adds it to a tar archive. This process has no limits and will add files
to the tar archive until that is no longer possible and limited by the
underlying operating system. This change automatically prunes the backup
file and retains only the last 15 inventory files. This should provide
the same backup capabilities we've had without trying to saving
archives indefinitely.

> It should be noted that this change is using a subprocess call to
  prune the tar file. This is being done because the "tarfile" library
  does not provide an interface for deleting a file within an archive.

Change-Id: Ida5a9be0d0910c223fe05401bc4f75aef100e456
Closes-Bug: #1750233
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

osa_toolkit/filesystem.py

@@ -21,10 +21,12 @@ import datetime
 import json
 import logging
 import os
-from osa_toolkit import dictutils as du
+import subprocess
 import tarfile
 import yaml
 
+from osa_toolkit import dictutils as du
+
 
 logger = logging.getLogger('osa-inventory')
 
@@ -154,6 +156,19 @@ def _make_backup(backup_path, source_file_path):
         'backup_openstack_inventory.tar'
     )
     with tarfile.open(inventory_backup_file, 'a') as tar:
+        # tar.getmembers() is always ordered with the
+        # tar standard append file order
+        members = [i.name for i in tar.getmembers()]
+        if len(members) > 15:
+            with open(os.devnull, 'w') as null:
+                for member in members[:-15]:
+                    subprocess.call(
+                        ['tar', '-vf', inventory_backup_file,
+                         '--delete', member],
+                        stdout=null,
+                        stderr=subprocess.STDOUT
+                    )
+
         basename = os.path.basename(source_file_path)
         backup_name = _get_backup_name(basename)
         tar.add(source_file_path, arcname=backup_name)

releasenotes/notes/limit-inventory-backkups.yaml-c96577e9de284cf2.yaml

@@ -0,0 +1,7 @@
+---
+
+issues:
+ - We are limiting the tarred inventory backups to 15 in addition to changes
+   that only apply backups when the config has changed. These changes are to
+   address an issue where the inventory was corruped with parallel runs on
+   large clusters.