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[Tim Bentley <1117334@xxxxxxxxxxxxxxxxxx>]

** Changed in: openlp/trunk
       Status: New => Won't Fix

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https://bugs.launchpad.net/bugs/1117334

Title:
  can't open/preview a song if db connection is interrupted (mysql)

Status in OpenLP:
  New
Status in OpenLP trunk series:
  Won't Fix

Bug description:
  Hi.

  Discovered the following error if OpenLP looses a connection to MySQL.

  Scenario: OpenLP configured to use MySQL instead of SQLite.
  Environment: Ubuntu 10.04 LTS, localhost for MySQL.

  On starting OpenLP, it holds open two connections to MySQL. These are
  seen as having growing 'sleep' durations in MySQL by executing "show
  process" whilst OpenLP is dormant/not using the DB.

  If there is a connection issue, either due to a network timeout, or
  forced connection kill - of at least one of these two persistent
  connections, when opening/previewing a song in the GUI, the following
  debug is displayed:

  Traceback (most recent call last):
    File "/usr/lib/pymodules/python2.6/openlp/core/lib/mediamanageritem.py", line 474, in onDoubleClicked
      self.onPreviewClick()
    File "/usr/lib/pymodules/python2.6/openlp/core/lib/mediamanageritem.py", line 496, in onPreviewClick
      serviceItem = self.buildServiceItem()
    File "/usr/lib/pymodules/python2.6/openlp/core/lib/mediamanageritem.py", line 590, in buildServiceItem
      if self.generateSlideData(serviceItem, item, xmlVersion, remote):
    File "/usr/lib/pymodules/python2.6/openlp/plugins/songs/lib/mediaitem.py", line 501, in generateSlideData
      song = self.plugin.manager.get_object(Song, item_id)
    File "/usr/lib/pymodules/python2.6/openlp/core/lib/db.py", line 323, in get_object
      return self.session.query(object_class).get(key)
    File "/usr/lib/pymodules/python2.6/sqlalchemy/orm/query.py", line 507, in get
      return self._get(key, ident)
    File "/usr/lib/pymodules/python2.6/sqlalchemy/orm/query.py", line 1500, in _get
      return q.all()[0]
    File "/usr/lib/pymodules/python2.6/sqlalchemy/orm/query.py", line 1267, in all
      return list(self)
    File "/usr/lib/pymodules/python2.6/sqlalchemy/orm/query.py", line 1361, in __iter__
      return self._execute_and_instances(context)
    File "/usr/lib/pymodules/python2.6/sqlalchemy/orm/query.py", line 1364, in _execute_and_instances
      result = self.session.execute(querycontext.statement, params=self._params, mapper=self._mapper_zero_or_none())
    File "/usr/lib/pymodules/python2.6/sqlalchemy/orm/session.py", line 753, in execute
      clause, params or {})
    File "/usr/lib/pymodules/python2.6/sqlalchemy/engine/base.py", line 824, in execute
      return Connection.executors[c](self, object, multiparams, params)
    File "/usr/lib/pymodules/python2.6/sqlalchemy/engine/base.py", line 872, in _execute_clauseelement
      parameters=params
    File "/usr/lib/pymodules/python2.6/sqlalchemy/engine/base.py", line 938, in __create_execution_context
      return dialect.execution_ctx_cls(dialect, connection=self, **kwargs)
    File "/usr/lib/pymodules/python2.6/sqlalchemy/engine/default.py", line 170, in __init__
      self.cursor = self.create_cursor()
    File "/usr/lib/pymodules/python2.6/sqlalchemy/engine/default.py", line 258, in create_cursor
      return self._connection.connection.cursor()
    File "/usr/lib/pymodules/python2.6/sqlalchemy/engine/base.py", line 576, in connection
      raise exc.InvalidRequestError("Can't reconnect until invalid transaction is rolled back")
  InvalidRequestError: Can't reconnect until invalid transaction is rolled back

  Note that this was initially seen after OpenLP was left running, and
  therefore connected to MySQL, overnight. After the overnight period,
  an attempt was made to open/preview a song and the above error was
  displayed. At this stage I don't know why the connections were closed
  - the server was localhost, the db uptime is days, and there was no
  laptop suspend during the overnight period.

  Thoughts on why it can't reconnect correctly?

  To recreate, configure OpenLP to use a MySQL database (not forgetting,
  on ubuntu, to install the package python-mysqldb otherwise you get
  "module not found" errors), and configuring the [songs] section for
  mysql, as described on the FAQ wiki page.

  Then start OpenLP and observe output of "show process", or use the
  "processes" tab if using phpmyadmin to observe the database server.
  Kill one or both connections. Attempt to open/preview a song, and the
  result is as above.

  
  npf@pc-n993019:~$ dpkg --list|grep openlp
  ii  openlp                                   1.9.12+bzr2117-0ubuntu1~lucid1                        Church lyrics projection application

  --d.

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