Improve tracking of segments and segment utilization.

[cumulus.git] / python / cumulus / __init__.py

diff --git a/python/cumulus/__init__.py b/python/cumulus/__init__.py
index ff811b0..a40c58d 100644 (file)
--- a/python/cumulus/__init__.py
+++ b/python/cumulus/__init__.py
@@ -1,3 +1,21 @@
+# Cumulus: Efficient Filesystem Backup to the Cloud
+# Copyright (C) 2008-2009, 2012 The Cumulus Developers
+# See the AUTHORS file for a list of contributors.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
 """High-level interface for working with Cumulus archives.
 
 This module provides an easy interface for reading from and manipulating
@@ -9,7 +27,7 @@ various parts of a Cumulus archive:
 """
 
 from __future__ import division
-import os, re, sha, tarfile, tempfile, thread
+import hashlib, os, re, tarfile, tempfile, thread
 from pysqlite2 import dbapi2 as sqlite3
 
 import cumulus.store, cumulus.store.file
@@ -56,7 +74,9 @@ class Struct:
         return "<%s %s>" % (self.__class__, self.__dict__)
 
 CHECKSUM_ALGORITHMS = {
-    'sha1': sha.new
+    'sha1': hashlib.sha1,
+    'sha224': hashlib.sha224,
+    'sha256': hashlib.sha256,
 }
 
 class ChecksumCreator:
@@ -512,7 +532,26 @@ class LocalDatabase:
         schemes.sort()
         return schemes
 
-    def garbage_collect(self, scheme, intent=1.0):
+    def list_snapshots(self, scheme):
+        """Return a list of snapshots for the given scheme."""
+        cur = self.cursor()
+        cur.execute("select name from snapshots")
+        snapshots = [row[0] for row in cur.fetchall()]
+        snapshots.sort()
+        return snapshots
+
+    def delete_snapshot(self, scheme, name):
+        """Remove the specified snapshot from the database.
+
+        Warning: This does not garbage collect all dependent data in the
+        database, so it must be followed by a call to garbage_collect() to make
+        the database consistent.
+        """
+        cur = self.cursor()
+        cur.execute("delete from snapshots where scheme = ? and name = ?",
+                    (scheme, name))
+
+    def prune_old_snapshots(self, scheme, intent=1.0):
         """Delete entries from old snapshots from the database.
 
         Only snapshots with the specified scheme name will be deleted.  If
@@ -559,6 +598,16 @@ class LocalDatabase:
             first = False
             max_intent = max(max_intent, snap_intent)
 
+        self.garbage_collect()
+
+    def garbage_collect(self):
+        """Garbage-collect unreachable segment and object data.
+
+        Remove all segments and checksums which is not reachable from the
+        current set of snapshots stored in the local database.
+        """
+        cur = self.cursor()
+
         # Delete entries in the segments_used table which are for non-existent
         # snapshots.
         cur.execute("""delete from segments_used
@@ -570,16 +619,10 @@ class LocalDatabase:
         cur.execute("""delete from segments where segmentid not in
                            (select segmentid from segments_used)""")
 
-        # Delete unused objects in the block_index table.  By "unused", we mean
-        # any object which was stored in a segment which has been deleted, and
-        # any object in a segment which was marked for cleaning and has had
-        # cleaning performed already (the expired time is less than the current
-        # largest snapshot id).
+        # Delete dangling objects in the block_index table.
         cur.execute("""delete from block_index
-                       where segmentid not in (select segmentid from segments)
-                          or segmentid in (select segmentid from segments
-                                           where expire_time < ?)""",
-                    (last_snapshotid,))
+                       where segmentid not in
+                           (select segmentid from segments)""")
 
         # Remove sub-block signatures for deleted objects.
         cur.execute("""delete from subblock_signatures