Running the data sampler tool from the penny library causes a ClassNotFoundException for a netty class. Per the mailing list, this is because the netty classes are not accessible to Penny.
I've attached a patch that adds netty to the penny jar.
For reference, I'm running a simple script that uses pig test data from
x = LOAD 'jsTst1.txt' USING PigStorage('\t');
x_filtered = FILTER x BY (int)$1 > 100;
STORE x_filtered INTO 'jsTst1Filtered';