Re: concurrent synchronization of nnmaildir directories

[prj@po.cwru.edu (Paul Jarc)]

James Leifer <James.Leifer@inria.fr> wrote:
> In particular, is it safe to do the following operations while
> nnmaildir is *running*?
>
> * Add a new message with its marks, i.e. add a file in foo/cur and
>   update foo/.nnmaildir/{marks/{read,reply,...},nov} appropriately.

Should be safe, I think.  I'd add the message before the marks.
Otherwise, if you happen to be exiting the group in Gnus at the same
time, nnmaildir would delete the (seemingly useless) marks if the
message doesn't exist yet.

> * Modify the marks of an existing message, i.e. add and delete entries
>   in foo/.nnmaildir/marks/{read,reply,...}

Safe.

> * Delete an existing message, i.e. delete a file in foo/cur and the
>   corresponding entries in foo/.nnmaildir/{marks/{read,reply,...},nov}.

Safe.  nnmaildir will clean up the cruft in .nnmaildir on its own
later on, at *Summary* exit.

> Is it dangerous to do these operations while nnmaildir is regenerating
> nov data, reading or saving marks, etc?

nnmaildir will use whatever data is there when it happens to look.
So, e.g., a message might have been added, but its marks may not be
there yet, so in Gnus, the message will seem to lack some marks it
should have.  If it's a problem for you for that to happen, then don't
do that.  nnmaildir will pick up the rest of the data the next time it
checks the filesystem, so the situation should straighten itself out
eventually, but there could be problematic cases: e.g., removing the
'expire mark on an old message that's about to be deleted will not
reliably save the message if you do it at the same time as expiry;
expiry might hit the message first.

> Do I need to do anything to foo/.nnmaildir/num?

No.  It's best to let nnmaildir manage that.


paul