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1 | #------------------------------------------------------------------------ |
2 | # | |
3 | # Copyright (C) 2000 Autonomous Zone Industries | |
4 | # | |
5 | # License: This is free software. You may use this software for any | |
6 | # purpose including modification/redistribution, so long as | |
7 | # this header remains intact and that you do not claim any | |
8 | # rights of ownership or authorship of this software. This | |
9 | # software has been tested, but no warranty is expressed or | |
10 | # implied. | |
11 | # | |
12 | # Author: Gregory P. Smith <greg@electricrain.com> | |
13 | # | |
14 | # Note: I don't know how useful this is in reality since when a | |
15 | # DBLockDeadlockError happens the current transaction is supposed to be | |
16 | # aborted. If it doesn't then when the operation is attempted again | |
17 | # the deadlock is still happening... | |
18 | # --Robin | |
19 | # | |
20 | #------------------------------------------------------------------------ | |
21 | ||
22 | ||
23 | # | |
24 | # import the time.sleep function in a namespace safe way to allow | |
25 | # "from bsddb.db import *" | |
26 | # | |
27 | from time import sleep as _sleep | |
28 | ||
29 | import db | |
30 | ||
31 | # always sleep at least N seconds between retrys | |
32 | _deadlock_MinSleepTime = 1.0/64 | |
33 | # never sleep more than N seconds between retrys | |
34 | _deadlock_MaxSleepTime = 3.14159 | |
35 | ||
36 | # Assign a file object to this for a "sleeping" message to be written to it | |
37 | # each retry | |
38 | _deadlock_VerboseFile = None | |
39 | ||
40 | ||
41 | def DeadlockWrap(function, *_args, **_kwargs): | |
42 | """DeadlockWrap(function, *_args, **_kwargs) - automatically retries | |
43 | function in case of a database deadlock. | |
44 | ||
45 | This is a function intended to be used to wrap database calls such | |
46 | that they perform retrys with exponentially backing off sleeps in | |
47 | between when a DBLockDeadlockError exception is raised. | |
48 | ||
49 | A 'max_retries' parameter may optionally be passed to prevent it | |
50 | from retrying forever (in which case the exception will be reraised). | |
51 | ||
52 | d = DB(...) | |
53 | d.open(...) | |
54 | DeadlockWrap(d.put, "foo", data="bar") # set key "foo" to "bar" | |
55 | """ | |
56 | sleeptime = _deadlock_MinSleepTime | |
57 | max_retries = _kwargs.get('max_retries', -1) | |
58 | if _kwargs.has_key('max_retries'): | |
59 | del _kwargs['max_retries'] | |
60 | while 1: | |
61 | try: | |
62 | return function(*_args, **_kwargs) | |
63 | except db.DBLockDeadlockError: | |
64 | if _deadlock_VerboseFile: | |
65 | _deadlock_VerboseFile.write( | |
66 | 'dbutils.DeadlockWrap: sleeping %1.3f\n' % sleeptime) | |
67 | _sleep(sleeptime) | |
68 | # exponential backoff in the sleep time | |
69 | sleeptime *= 2 | |
70 | if sleeptime > _deadlock_MaxSleepTime: | |
71 | sleeptime = _deadlock_MaxSleepTime | |
72 | max_retries -= 1 | |
73 | if max_retries == -1: | |
74 | raise | |
75 | ||
76 | ||
77 | #------------------------------------------------------------------------ |