[racket-dev] atomic file update by write & rename... not!

On Thu, Jan 13, 2011 at 3:40 PM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> At Thu, 13 Jan 2011 16:30:08 -0500, Eli Barzilay wrote:
>> 15 minutes ago, Matthew Flatt wrote:
>> > Is there anything else in the main distribution that is uses
>> > `rename-file-or-directory' for atomic update?
>>
>> Is the handin-server's use kosher?  There are three uses of it, and
>> the only one that looks suspicious is the last one, where "ATTEMPT" is
>> renamed to "SUCCESS-0".
>
> Those are directories, and you can't move to an existing directory name
> on any platform, right?
>
> I think the handin server probably depends on non-concurrent handins
> for a given account, though, since it shuffles many files and
> directories around. Probably it should use some sort of lock to enforce
> non-concurrency.

In general, it seems like the handin server can safely make the
assumption that there is only one sever running for a given directory
and thus can do all of the syncronization at the Racket level (unlike
the preferences file).

Hopefully the preferences file is the only place (and things like raco
setup where we know we're creating lots of processes).

Robby