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 co
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.
If you want the code to happen on only one machine, why not run it in your
driver program that submits the MapReduce job?
You could also create a special input record that tells the mapper who gets
that record that it's the chosen one. However, note that that mapper may be run
multiple times du
Another approach would be to use a custom InputFormat implementation,
with the flag as a property of the input split . Consider wrapping your
InputFormat with something like 'InputFormatWithFlag', that returns
splits that combine the wrapped InputFormat's splits with your flag.
Since InputForm
From top of my head, you could set the flag to true based on some
globally unique condition.
Like some specific file name with start offset 0 - like part-0,
offset 0 (the actual file name could be a jobconf param).
Note that the condition should be repeatable - since tasks can get
reexe
