Created attachment 53045 [details]
File which crashes the indexer

Here's the backtrace:

DEBUG: +file:///disk/b/mail/Mail/group-2002-02/351

Unhandled Exception: System.ArgumentNullException: null key
Parameter name: key
in [0x000c7] System.Collections.Hashtable:Find (System.Object key)
in [0x00002] (at /tmp/scratch/BUILD/mono-1.1.8.3/mcs/class/corlib/System.Collect
ions/Hashtable.cs:395) System.Collections.Hashtable:Contains (System.Object key)
in <0x00231> Beagle.Util.Scheduler:Worker ()
in (wrapper delegate-invoke) System.MulticastDelegate:invoke_void ()

I am not at all convinced that the file shown in the DEBUG log as the most
recently indexed is the problem -- I've seen another half-dozen of these
crashes, some of the files look very inocuous, and in at least one case there
was no indexing going on at all, i.e. the log looks like this:

DEBUG: Done crawling '/disk/b/mail/Mail/pers-2002-05'
DEBUG: Done crawling '/disk/b/mail/Mail/pers-2002-06'
DEBUG: Done crawling '/disk/b/mail/Mail/pers-2002-07'
DEBUG: Done crawling '/disk/b/mail/Mail/pers-2002-08'
DEBUG: Done crawling '/disk/b/mail/Mail/pers-2002-09'

Unhandled Exception: System.ArgumentNullException: null key
Parameter name: key
in [0x000c7] System.Collections.Hashtable:Find (System.Object key)
in [0x00002] (at /tmp/scratch/BUILD/mono-1.1.8.3/mcs/class/corlib/System.Collect
ions/Hashtable.cs:395) System.Collections.Hashtable:Contains (System.Object key)
in <0x00231> Beagle.Util.Scheduler:Worker ()
in (wrapper delegate-invoke) System.MulticastDelegate:invoke_void ()
INFO: NetBeagleConfigurationChanged EventHandler invoked
INFO: WebServicesConfigurationChanged EventHandler invoked

Created attachment 53091 [details] [review]
Patch to catch the null Source problem

So it now seems clear the problem is not with the data
I have now been running for 12 hours with the attached patch, which has fired 20
times (Tag always empty also) in the course of indexing 65000 files in 250
directories.  Any suggestions about more information to log when the null Source
is detected would be welcome.

Created attachment 53108 [details] [review]
Always enforce non-null task source

Thanks for investigating that. I tracked it down to KopeteQueryable running
without inotify, and raddy on IRC happened to report this at the same time.
This is now fixed in CVS.

I'm attaching another patch for review which would prevent this problem
reoccurring so subtly in future.

Created attachment 53109 [details] [review]
IndexSynchronization fix

This fixes another source of tasks without Source. This one is different as the
task is created in static context. This sets the source to the lock object,
which should do the trick..?

Yeah, both of these patches are good.  Please commit.