OperationalError: database is locked

[sascha_silbe]

While trying to modify bug #137, I got the following error. Second try worked fine.
Looks like trac should wait for the lock (up to a timeout of course) and try again instead of bailing out.

How to Reproduce

While doing a POST operation on /ticket/137, Trac issued an internal error.

(please provide additional details here)

Request parameters:

{'__FORM_TOKEN': u'3f28aa22b769ed9b5a66fecc',
 'action': u'leave',
 'action_reassign_reassign_owner': u'sascha_silbe',
 'action_resolve_resolve_resolution': u'fixed',
 'cnum': u'4',
 'comment': u"hulahop in git seems to work the other way around now: using the full version for the path instead of major.minor only. This works on Fedora and Ubuntu, but breaks on Debian. Any chance we could support both schemes?\r\nI currently need to follow xulrunner closely to ensure security updates are applied in sugar-jhbuild. For CVE-2009-1169 and CVE-2009-1044 I even need to pull distro patches since there's still no new upstream release containing the fixes (1 week and counting).\r\n\r\n",
 'field_cc': u'sascha_silbe',
 'field_component': u'hulahop',
 'field_distribution': u'Ubuntu',
 'field_keywords': u'',
 'field_milestone': u'0.86',
 'field_priority': u'Normal',
 'field_severity': u'Major',
 'field_status_field': u'New',
 'field_summary': u'Use standalone glue not rpath linking for xulrunner',
 'field_type': u'defect',
 'field_version': u'0.83.x',
 'id': u'137',
 'replyto': u'',
 'submit': u'Submit changes',
 'ts': u'2009-02-12 13:24:51+00:00'}

System Information

Trac	0.11.1
Python	2.5.2 (r252:60911, Jul 31 2008, 18:03:07) [GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)]
setuptools	0.6c8
SQLite	3.4.2
pysqlite	2.3.2
Genshi	0.5.1

Python Traceback

Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/web/main.py", line 423, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/web/main.py", line 197, in dispatch
    resp = chosen_handler.process_request(req)
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/ticket/web_ui.py", line 170, in process_request
    return self._process_ticket_request(req)
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/ticket/web_ui.py", line 494, in _process_ticket_request
    self._do_save(req, ticket, action)
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/ticket/web_ui.py", line 989, in _do_save
    cnum=internal_cnum):
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/ticket/model.py", line 260, in save_changes
    (self[name], self.id))
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/db/util.py", line 50, in execute
    return self.cursor.execute(sql_escape_percent(sql), args)
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/db/sqlite_backend.py", line 58, in execute
    args or [])
  File "/usr/lib/python2.5/site-packages/Trac-0.11.1-py2.5.egg/trac/db/sqlite_backend.py", line 50, in _rollback_on_error
    return function(self, *args, **kwargs)
OperationalError: database is locked