[Dovecot] New mailbox format

[Tom Metro]

Timo Sirainen wrote:
> Index File
> ----------
[...]
> The file is modified by creating first exclusively owned "index.lock" file,
> updating it and then rename()ing it over the index file. This lock file
> shouldn't be held for a long time, so if it exists, and it doesn't get 
> modified at all within 30 seconds, it can be overwritten. Before
> rename()ing over the index file, you should check with stat() that the
> index.lock file is still the same as you expect it to be (in case your
> process was temporarily stopped for over 30 secs).

The locking and handling of the index strikes me as a regression back to 
the mbox problems that Maildir tried to solve.

Have you considered other approaches, such as having the index be under 
control of a daemon, and use IPC to communicate events to that daemon, 
which could then exclusively handle modifying the file?

Or maybe a fixed size record structure, which would permit more of a 
random record access and modification with less chance of inter process 
conflicts?

Any way you slice it, though, these are just approximations of a 
database server. Maybe embedding SQLite (just for indexes) is the answer?

  -Tom