[ditrack commit] r2368 - src/trunk/DITrack/DB

[Vlad Skvortsov]

Oleg,

please create a separate branch (and include that in autotest) for the
follow-up changes, as agreed.

My comments inline.

Author: oleg
Date: 2007-11-18 09:09:52 -0800 (Sun, 18 Nov 2007)
New Revision: 2368
src/trunk/DITrack/DB/Cache.py
added simple cache interface
Added: src/trunk/DITrack/DB/Cache.py
===================================================================
--- src/trunk/DITrack/DB/Cache.py (rev 0)
+++ src/trunk/DITrack/DB/Cache.py 2007-11-18 17:09:52 UTC (rev 2368)
@@ -0,0 +1,75 @@
+#
+# Cache.py - cache interface
+#
+# Copyright (c) 2006-2007 The DITrack Project, www.ditrack.org.

...2008.

+#
+# $Id$
+# $HeadURL$
+#
+# Redistribution and use in source and binary forms, with or without
+#
+# * Redistributions of source code must retain the above copyright notice,
+# this list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+
+import time
+
+# DITrack modules
+import DITrack.DB.Common
+
+CACHE_EXPIRED_TIME = 6 # in hours (numeric type only)

Why do we need time-based expiration? I think we should rely on actual
changes (read: commits to the database tree) and the time passed since
we cached data doesn't make any difference for us.

+CACHE_FILE = "cache"
+CACHE_VERSION = "0.1"

Why not just "1"?

+
+#
+# Classes
+#
+
+ """
+ Class encapsulating cache operations.
+ """

...cache of what?

+
+ self.cache.close()

My recent experience with closing shelves from destructors suggests that
this kind of finalization should be better avoided. Sometimes the
objects are still mysteriously referenced from somewhere else and the
data doesn't get flushed to the disk. I'm not sure whether we should add
an explicit method to close the shelve here.

+
+ """
+ PATH is a path to an issue database
+ """

Missing trailing period.

+ self.cache = DITrack.DB.Common.open_shelving(path, CACHE_FILE)
+

Comment?

+ return len(self.get())
+

Comment?

+ self.cache["data"] = []
+

Comment?

+ if ("data" in self.cache and self.cache["expired_time"] > time.time()
+ return self.cache["data"]
+ return []
+

Comment?

+ self.cache["data"] = issues
+ self.cache["expired_time"] = time.time() + CACHE_EXPIRED_TIME * 3600
+ self.cache["version"] = CACHE_VERSION