Trap exceptions from invalid database connection string

[Ryan J Ollos]

This is a continuation of the work in #11189, attempting to raise helpful error messages for cases that the [trac] database string is invalid.

Proposed changes can be found in log:rjollos.git:t11415.

[Ryan J Ollos]

Narrowing focus for 1.0.5.

[Jun Omae]

Hmmm, I get unit tests failing on PostgreSQL and MySQL after rebasing proposed changes on 1.0-stable.

psycopg2.ProgrammingError: schema "tractest" already exists

make: *** [unit-test] Error 1

_mysql_exceptions.OperationalError: (1050, "Table 'system' already exists")
make: *** [unit-test] Error 1

Revised changes in jomae.git@t11415.2.

[Jun Omae]

Revised again in [9e454a430/jomae.git]. I moved check for existence of SQLite database from api.py to sqlite_backend.py and added tests/sqlite_test.py.

[Ryan J Ollos]

Feel free to re-assign ticket. I'm not sure I'll have time to look at the changes more closely within the next week or so.

[Jun Omae]

Okay. I'll fix it.

I noticed that SQLiteConnection.__init__ already checks existence of database file at tags/trac-1.0.5/trac/db/sqlite_backend.py@:265-266#L252​. It doesn't need to add another check.

I found a rare issue. It can be reproduced with Trac 1.0.5 if SQLite database file is missing (or not permitted to read) and [trac] repository_sync_per_request is empty.

2015-04-18 23:24:17,312 Trac[main] ERROR: can't retrieve session: TimeoutError: Unable to get database connection within 0 seconds. (AttributeError: NullTranslationsBabel instance has no attribute 'isactive')

[Jun Omae]

2015-04-18 23:24:17,312 Trac[main] ERROR: can't retrieve session: TimeoutError: Unable to get database connection within 0 seconds. (AttributeError: NullTranslationsBabel instance has no attribute 'isactive')

Proposed changes in [55657979c/jomae.git].

If SQLiteConnection.__init__ uses Babel's LazyProxy instance for translated messages, trac.db.pool recursively tries to connect database to retrieve user's locale. PooledConnection wrongly is constructed with a tuple instance for the cnx argument. After this, the following AttributeError is raised inside translation.isactive property. As the result, the AttributeError is converted to AttributeError: NullTranslationsBabel instance has no attribute 'isactive'.

Traceback (most recent call last):
  File "/home/jun66j5/src/tracdev/git/trac/util/translation.py", line 183, in isactive
    self.activate(get_locale(), env_path)
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 499, in <lambda>
    translation.make_activable(lambda: req.locale, env.path if env else None)
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 355, in __getattr__
    value = self.callbacks[name](self)
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 289, in _get_locale
    preferred = req.session.get('language')
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 355, in __getattr__
    value = self.callbacks[name](self)
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 281, in _get_session
    return Session(self.env, req)
  File "/home/jun66j5/src/tracdev/git/trac/web/session.py", line 210, in __init__
    self.get_session(sid)
  File "/home/jun66j5/src/tracdev/git/trac/web/session.py", line 233, in get_session
    super(Session, self).get_session(sid, authenticated)
  File "/home/jun66j5/src/tracdev/git/trac/web/session.py", line 85, in get_session
    """, (sid, int(authenticated))):
  File "/home/jun66j5/src/tracdev/git/trac/db/util.py", line 127, in execute
    cursor = self.cnx.cursor()
  File "/home/jun66j5/src/tracdev/git/trac/db/util.py", line 115, in __getattr__
    return getattr(self.cnx, name)
AttributeError: 'tuple' object has no attribute 'cursor'

I'm going to push these changes.

[Jun Omae]

Committed in [13999-14000] and merged to trunk in [14001].