API request handling failure

[cmouse]

I get this in logs occasionally when browsing the Web UI.

2016-04-22 11:25:42+0300 [-] while handling API request

Traceback (most recent call last):

File "/opt/buildbot/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1126, in _inlineCallbacks

result = result.throwExceptionIntoGenerator(g)

File "/opt/buildbot/local/lib/python2.7/site-packages/twisted/python/failure.py", line 389, in throwExceptionIntoGenerator

return g.throw(self.type, self.value, self.tb)

File "/opt/buildbot/local/lib/python2.7/site-packages/buildbot/www/rest.py", line 407, in renderRest

request.write(data)

File "/usr/lib/python2.7/contextlib.py", line 35, in exit

self.gen.throw(type, value, traceback)

--- <exception caught here> ---

File "/opt/buildbot/local/lib/python2.7/site-packages/buildbot/www/rest.py", line 124, in handleErrors

yield

File "/opt/buildbot/local/lib/python2.7/site-packages/buildbot/www/rest.py", line 339, in renderRest

data = yield ep.get(rspec, kwargs)

File "/opt/buildbot/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1126, in _inlineCallbacks

result = result.throwExceptionIntoGenerator(g)

File "/opt/buildbot/local/lib/python2.7/site-packages/twisted/python/failure.py", line 389, in throwExceptionIntoGenerator

return g.throw(self.type, self.value, self.tb)

File "/opt/buildbot/local/lib/python2.7/site-packages/buildbot/data/changes.py", line 73, in get

changes = yield self.master.db.changes.getChangesForBuild(buildid)

File "/opt/buildbot/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1128, in _inlineCallbacks

result = g.send(result)

File "/opt/buildbot/local/lib/python2.7/site-packages/buildbot/db/changes.py", line 196, in getChangesForBuild

if change and changechangeid? != toChanges.get(cb, {}).get('changeid'):

exceptions.AttributeError?: 'NoneType?' object has no attribute 'get'

[rayalan]

It also happens with building periodically (via rebuild). Problem is in line 196 in buildbot/db/changes.py where the line should read if change and change['changeid'] != (toChanges.get(cb) or {}).get('changeid'): rather than the current if change and change['changeid'] != toChanges.get(cb, {}).get('changeid')

There are a couple ways that the codebase can set to None (such as the toChanges[cb] = {'changeid': None} line on 192), and the line just errors out when those are hit.

I'm working on a patch; the fix is much easier than proving it with a unit test change.

[rayalan]

Proposed patch here: ​https://github.com/buildbot/buildbot/pull/2163.

[dustin]

Setting to 0.9.0 since there's a patch pending