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Opened 9 years ago

Closed 9 years ago

Last modified 4 years ago

#9623 closed defect (fixed)

PostgreSQL authentication error throws cryptic exception

Reported by: gabrtv Owned by: Christian Boos
Priority: normal Milestone: 0.12.1
Component: database backend Version: 0.12-stable
Severity: normal Keywords: error, postgresql, database, apache, modpython
Cc: Jonas Borgström Branch:
Release Notes:
API Changes:

Description

After issuing a GET to /trac, Apache/mod-python return the following cryptic error message:

Traceback (most recent call last):
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/web/api.py", line 436, in send_error
    data, 'text/html')
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/web/chrome.py", line 803, in render_template
    message = req.session.pop('chrome.%s.%d' % (type_, i))
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/web/api.py", line 212, in __getattr__
    value = self.callbacks[name](self)
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/web/main.py", line 300, in _get_session
    return Session(self.env, req)
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/web/session.py", line 166, in __init__
    self.promote_session(sid)
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/web/session.py", line 225, in promote_session
    @self.env.with_transaction()
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/db/api.py", line 82, in transaction_wrapper
    ldb.rollback()
  File "/usr/local/lib/python2.6/dist-packages/Trac-0.12.1dev_r10109-py2.6.egg/trac/db/util.py", line 102, in __getattr__
    return getattr(self.cnx, name)
AttributeError: 'tuple' object has no attribute 'rollback'

The error should probably be a bit more descriptive. Environment is Ubuntu 10.04 x64 with a generic trac 0.12 install.

Attachments (1)

9623-active.patch (1.9 KB ) - added by Christian Boos 9 years ago.
more robust deferred operations when taking a connection from the pool.

Download all attachments as: .zip

Change History (10)

comment:1 by osimons, 9 years ago

I just looked at this briefly when it appeard on IRC, and according to user the error was a Postgres authentication error - which is then a typical database error that can occur for various reasons. Some assumption inside transaction_wrapper does not hold in such circumstances.

comment:2 by Christian Boos, 9 years ago

I wonder if we still have a similar error with 0.12-stable, as the pool code has changed quite a bit. Would someone mind testing? (or I'll test it myself on some innocent 0.12-stable instance, like … Bitten! :-) ).

comment:3 by Christian Boos, 9 years ago

Milestone: 0.12.1
Owner: set to Christian Boos
Status: newassigned

This can actually happen as a secondary error, if a database connection couldn't be created (the ('create', None) entry is kept in the _active dict). I have already fixed that in the forthcoming changes in the db layer for 0.13dev, need to backport this specific fix.

comment:4 by Christian Boos, 9 years ago

Specifically this hunk:

  • trac/db/pool.py

    a b  
    11398            elif op == 'close':
    11499                cnx.close()
    115100            if op in ('close', 'create'):
    116                 cnx = connector.get_connection(**kwargs)
    117 
     101                try:
     102                    cnx = connector.get_connection(**kwargs)
     103                except Exception: # couldn't create a new connection
     104                    with self._available:
     105                        del self._active[(tid, key)]
     106                    raise
     107       

by Christian Boos, 9 years ago

Attachment: 9623-active.patch added

more robust deferred operations when taking a connection from the pool.

comment:5 by Christian Boos, 9 years ago

Ok, I backported and refined the patch above. Please test 9623-active.patch. I think it's a safe fix but more review can't hurt, especially that close to release ;-)

comment:6 by Remy Blank, 9 years ago

The patch works fine here on Linux, OS X and Windows 7. But I have to admit that you have lost me long ago with the logic in the DB pool…

in reply to:  6 comment:7 by Christian Boos, 9 years ago

Cc: Jonas Borgström added
Component: generaldatabase backend

Replying to rblank:

The patch works fine here on Linux, OS X and Windows 7.

Thanks for testing! Ideally, we should also test what's happening when Trac is running fine with PostgreSQL or MySQL and the DB is suddenly shut down…

But I have to admit that you have lost me long ago with the logic in the DB pool…

Well, the story goes like that:

  • jonas produces a simple, nice and clean pool mechanism
  • some corner cases appear
  • cboos tries to handle them all and makes the whole thing overly complex…

Repeat. So let's wait for the next iteration from jonas ;-)

comment:8 by Christian Boos, 9 years ago

Resolution: fixed
Status: assignedclosed

Ok, as I was surprised to get again a TimeoutError when testing the patch, I realized this was because the database I attempted to connect to was no longer existing. So the 'create' deferred step failed, but we didn't show why.

I added that to the error message (appended, because of the string freeze), in addition to the previous changes from 9623-active.patch.

Fix committed in r10151.

comment:9 by Ryan J Ollos, 4 years ago

Keywords: postgres removed

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