Streaming window operations not producing output

[diogo]

Hi there, I'm trying to use Window operations on streaming, but everything
I perform a windowed computation, I stop getting results.

For example:

val wordCounts = pairs.reduceByKey(_ + _)
wordCounts.print()

Will print the output to the stdout on 'batch duration' interval. Now if I
replace it with:

val wordCounts = pairs.reduceByKeyAndWindow(_+_, _-_, Seconds(4),
Seconds(2))
wordCounts.print()

It will never output. What did I get wrong?

Thanks.