I think you need some kind of semaphore that you can turn on by the first
reducer. For example, allocating a file in HDFS would work - if you could
guarantee that it is an atomic operation (create-if-does-not-exist).
Mark
On Sat, Jan 2, 2010 at 10:04 PM, bharath v <
bharathvissapragada1...@gmail.com> wrote:
> Hi,
>
> I want a particular "section of code" to run only in any "ONE" of the
> mappers . So I employed the following procedure.
>
> Main-Class
> {
>
> public boolean flag = true;
>
> Map-Class
> {
> if(flag)
> {
>
> flag=false;
> /* section of code */
> }
>
>
> }
>
> I am running this code on in pseudo-distributed mode and its working fine .
> I doubt whether this runs correctly in distributed mode because , mappers
> on
> other systems have to notified of the changed "flag" .. Any Comments ? If
> this is wrong , any suggestions on what method I must follow to achieve
> this
> functionality in D-mode .
>
> Thanks
>
