blueprint nova-image-cache-management phase1

Phase 1 of the image-cache-management blueprint. Implement
checksumming and verification of base images, as well as
removal of base images which are not in use. Removal is
enabled with a flag.

Change-Id: Ib04a02075a103c2fef6716fd0ac87c41a3535d37

1 files changed, 8 insertions, 0 deletions

diff --git a/nova/utils.py b/nova/utils.py
index d1968ac4d0..f86b4ff1f4 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -22,6 +22,7 @@
 import contextlib
 import datetime
 import functools
+import hashlib
 import inspect
 import json
 import lockfile
@@ -1194,6 +1195,13 @@ def read_cached_file(filename, cache_info, reload_func=None):
     return cache_info['data']
 
 
+def hash_file(file_like_object):
+    """Generate a hash for the contents of a file."""
+    checksum = hashlib.sha1()
+    any(map(checksum.update, iter(lambda: file_like_object.read(32768), '')))
+    return checksum.hexdigest()
+
+
 @contextlib.contextmanager
 def temporary_mutation(obj, **kwargs):
     """Temporarily set the attr on a particular object to a given value then