Import PyBSDDB 3.4.0. Rename historical wrapper to bsddb185.

1 files changed, 69 insertions, 0 deletions

diff --git a/Lib/bsddb/dbutils.py b/Lib/bsddb/dbutils.py
new file mode 100644
index 0000000..fe08407
--- /dev/null
+++ b/Lib/bsddb/dbutils.py
@@ -0,0 +1,69 @@
+#------------------------------------------------------------------------
+#
+# In my performance tests, using this (as in dbtest.py test4) is
+# slightly slower than simply compiling _db.c with MYDB_THREAD
+# undefined to prevent multithreading support in the C module.
+# Using NoDeadlockDb also prevent deadlocks from mutliple processes
+# accessing the same database.
+#
+# Copyright (C) 2000 Autonomous Zone Industries
+#
+# License:      This is free software.  You may use this software for any
+#               purpose including modification/redistribution, so long as
+#               this header remains intact and that you do not claim any
+#               rights of ownership or authorship of this software.  This
+#               software has been tested, but no warranty is expressed or
+#               implied.
+#
+# Author: Gregory P. Smith <greg@electricrain.com>
+#
+# Note: I don't know how useful this is in reality since when a
+#       DBDeadlockError happens the current transaction is supposed to be
+#       aborted.  If it doesn't then when the operation is attempted again
+#       the deadlock is still happening...
+#       --Robin
+#
+#------------------------------------------------------------------------
+
+
+#
+# import the time.sleep function in a namespace safe way to allow
+# "from bsddb3.db import *"
+#
+from time import sleep
+_sleep = sleep
+del sleep
+
+import _db
+
+_deadlock_MinSleepTime = 1.0/64  # always sleep at least N seconds between retrys
+_deadlock_MaxSleepTime = 1.0     # never sleep more than N seconds between retrys
+
+
+def DeadlockWrap(function, *_args, **_kwargs):
+    """DeadlockWrap(function, *_args, **_kwargs) - automatically retries
+    function in case of a database deadlock.
+
+    This is a DeadlockWrapper method which DB calls can be made using to
+    preform infinite retrys with sleeps in between when a DBLockDeadlockError
+    exception is raised in a database call:
+
+        d = DB(...)
+        d.open(...)
+        DeadlockWrap(d.put, "foo", data="bar")  # set key "foo" to "bar"
+    """
+    sleeptime = _deadlock_MinSleepTime
+    while (1) :
+        try:
+            return apply(function, _args, _kwargs)
+        except _db.DBLockDeadlockError:
+            print 'DeadlockWrap sleeping ', sleeptime
+            _sleep(sleeptime)
+            # exponential backoff in the sleep time
+            sleeptime = sleeptime * 2
+            if sleeptime > _deadlock_MaxSleepTime :
+                sleeptime = _deadlock_MaxSleepTime
+
+
+#------------------------------------------------------------------------
+