Webstatus crash when viewing a builder

[ludovicchabant]

I frequently get this crash when I either want to view a builder's page, or a specific build's page:

web.Server Traceback (most recent call last):
twisted.internet.defer.FirstError: FirstError[#0, [Failure instance: Traceback (failure with no frames):
  <class 'twisted.internet.defer.FirstError'>:
    FirstError[#0, [Failure instance: Traceback:
      <type 'exceptions.TypeError'>: 'NoneType' object has no attribute '__getitem__' C:\Python27\lib\site-packages\twisted\internet\defer.py:575:_runCallbacks
D:\SnowMonkey\TnT\Build\Bin\SnowMonkey\buildbot\master\buildbot\util\lru.py:217:handle_result
C:\Python27\lib\site-packages\twisted\internet\defer.py:380:callback
C:\Python27\lib\site-packages\twisted\internet\defer.py:488:_startRunCallbacks --- <exception caught here> ---
C:\Python27\lib\site-packages\twisted\internet\defer.py:575:_runCallbacks
D:\SnowMonkey\TnT\Build\Bin\SnowMonkey\buildbot\master\buildbot\sourcestamp.py:120:<lambda>
D:\SnowMonkey\TnT\Build\Bin\SnowMonkey\buildbot\master\buildbot\changes\changes.py:55:fromChdict ]] ]]
twisted.internet.defer.FirstError:
  FirstError[#0, [Failure instance: Traceback (failure with no frames):
    <class 'twisted.internet.defer.FirstError'>:
      FirstError[#0, [Failure instance: Traceback:
        <type 'exceptions.TypeError'>:
          'NoneType' object has no attribute '__getitem__'
C:\Python27\lib\site-packages\twisted\internet\defer.py:575:_runCallbacks
D:\SnowMonkey\TnT\Build\Bin\SnowMonkey\buildbot\master\buildbot\util\lru.py:217:handle_result
C:\Python27\lib\site-packages\twisted\internet\defer.py:380:callback
C:\Python27\lib\site-packages\twisted\internet\defer.py:488:_startRunCallbacks --- <exception caught here> ---
C:\Python27\lib\site-packages\twisted\internet\defer.py:575:_runCallbacks
D:\SnowMonkey\TnT\Build\Bin\SnowMonkey\buildbot\master\buildbot\sourcestamp.py:120:<lambda>
D:\SnowMonkey\TnT\Build\Bin\SnowMonkey\buildbot\master\buildbot\changes\changes.py:55:fromChdict ]] ]]

It seems that "cache" in "None" in "Change.fromChdict".

The bug appears out of nowhere, i.e. one second it works, and the next it will fire all the time and I need to kill all the caches, along with the DB, and rebuild the master. Any idea what could be causing this? I could just quick-patch it and return "None" if "cache is None", but I'm not sure if that would be a proper fix or just delaying the problem.

[dustin]

Not quite - chdict is None, meaning that the change with that ID is not in the DB. I don't know why that would be the case.

The right fix is to add code to ignore changes that aren't in the DB in sourcestamp.py.

[dustin]

commit b4ffcdb1adeebff3bb601076903b3de1d78b7e37
Author: Dustin J. Mitchell <dustin@mozilla.com>
Date:   Sun Sep 1 10:52:52 2013 -0400

    Omit changes that aren't in the DB from sourcestamps
    
    Fixes #2554.

should fix this up.

[ludovicchabant]

Thanks! I'll report back if the bug shows up again... hopefully there won't be any reporting back :)