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Re: [Nmh-workers] Locking (specifically, sequences)
From: |
David Levine |
Subject: |
Re: [Nmh-workers] Locking (specifically, sequences) |
Date: |
Sun, 10 Mar 2013 11:53:09 -0400 |
Ken wrote:
> - The "complex" case, where the sequence file could
> potentially be changed from the time that it's first
> read until the sequence file needs to be manipulated.
> "inc" is an example; "pick" is another.
Is sortm in the same category as folder -pack?
> The basic issue there is if you add a new message to a
> folder, the long-running command wouldn't necessarily know
> the new message existed and thus when it wrote the new
> sequence file out it wouldn't write out any sequences that
> these new messages are in.
I'm worried about something else: concurrent read/write of
the sequences file. If two or more processes read it and
write it concurrently, the last one to write will destroy
everything that the other processes wrote. Locked-read-
write will detect that, but I'm not sure we can always
correct it. I don't have a concrete example of where we
can't, but it feels analogous to a merge conflict.
> adding new messages to a folder that you're currently
> inc'ing into is already not safe (messages could get
> overwritten).
How so? It depends what "adding" means, but I would limit
that to just nmh commands that can add a new message. I
think that's inc, refile, rcvstore, burst, and thing that
fcc's (comp, dist, forw, repl, mhmail). And I don't think
they'll overwrite a message that any other, even non-nmh,
program had created.
David
- Re: [Nmh-workers] Locking (specifically, sequences), (continued)
- Re: [Nmh-workers] Locking (specifically, sequences), Ken Hornstein, 2013/03/12
- Re: [Nmh-workers] Locking (specifically, sequences), Valdis . Kletnieks, 2013/03/12
- Re: [Nmh-workers] Locking (specifically, sequences), Ken Hornstein, 2013/03/12
- Re: [Nmh-workers] Locking (specifically, sequences), Valdis . Kletnieks, 2013/03/12
- Re: [Nmh-workers] Locking (specifically, sequences), Lyndon Nerenberg, 2013/03/12
- Re: [Nmh-workers] Locking (specifically, sequences), Lyndon Nerenberg, 2013/03/11
- Re: [Nmh-workers] Locking (specifically, sequences), Ken Hornstein, 2013/03/11
- Re: [Nmh-workers] Locking (specifically, sequences), Lyndon Nerenberg, 2013/03/11
- Re: [Nmh-workers] Locking (specifically, sequences), Ralph Corderoy, 2013/03/10
- Re: [Nmh-workers] Locking (specifically, sequences), Ken Hornstein, 2013/03/10
Re: [Nmh-workers] Locking (specifically, sequences),
David Levine <=
Re: [Nmh-workers] Locking (specifically, sequences), David Levine, 2013/03/10
Re: [Nmh-workers] Locking (specifically, sequences), David Levine, 2013/03/10