[Mailman-Users] Is it possible that a list loses its members?

Sebastian Hagedorn Hagedorn at uni-koeln.de
Tue May 20 22:16:15 CEST 2008

-- Mark Sapiro <mark at msapiro.net> is rumored to have mumbled on 20. Mai 
2008 10:52:34 -0700 regarding Re: [Mailman-Users] Is it possible that a 
list loses its members?:

>| I'm at a loss to explain what might have happened. Any ideas?
> I can't explain what happened, but the only way I can see something like
> this happening is if there was a failure in list locking.

Right, that's what we thought ourselves. The member adding is logged and we 
verifed that the notification mails got sent, but it appears that both 
those actions occur *before* the members are actually added.

> I.e. if some
> other process was updating the list at the same time that add_members
> was running and the other process locked the list first, then
> add_members locked the list, added the members and saved and unlocked
> the list, and finally the other process saved the list without the
> members.

The other process would probably(?) be the config_list command. Some more 
detail. We found the following just before the list was created:

May 09 14:54:25 2008 (10586) admin.py access for non-existent list: listname
May 09 14:54:25 2008 (11122) admin.py access for non-existent list: listname

The member adding happened just two minutes later:

May 09 14:56:29 2008 (13495) listname: new xxx.xxx at uni-koeln.de,

Now the script we use to create new lists does this:


new_list() calls newlist, config_list() calls config_list, and 
add_members() calls add_members - not much of a surprise, I guess.

> I don't think this can result from a simple failure of some process to
> lock the list since an unlocked list cannot be saved, and locking a list
> refreshes the data. If there is an issue, it has to be in the locking
> mechanism itself, but this seems sound and there are no known issues
> with this, although coincidentally (and I'm sure it's just a rare and
> strange coincidence) I saw an apparent locking failure last week. See
> <http://mail.python.org/pipermail/mailman-developers/2008-May/020190.html
> >.
> So now we have two reports of possible locking failures. We'll have to
> keep watching.

There were instances before where listowner talked of strange phenomena, 
but there never was any proof. I admit I never believed them ...
Sebastian Hagedorn - Listmaster - RZKR-R1 (Flachbau), Zimmer 18
Zentrum für angewandte Informatik - Universitätsweiter Service RRZK
Universität zu Köln / Cologne University - Tel. +49-221-478-5587

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