Problem when looping through multiple CSV lists of URLs

[Mark Hanford]

Hi, folks. I'm pretty new at JMeter, so apologies if this is either a daft
question, or I'm approaching the whole idea from the wrong angle.

I have a list of about 1000 URLs in our product that I need to hit and
measure. They are from various areas of the product, so it doesn't make
sense to compare them all as a single set, so they have been split into 10
files of ~100 URLs each.

I would like (I think) a bunch of threads to start up, and hit all 1000
pages, but I want each "HTTP Request" to have it's own name to distinguish
between them.

I've tried using a While Controller, which works for the first list, but it
never runs any subsequent ones:

Test Plan
    Thread Group
        While Controller
                CSV Data Set Config - data-a.csv
                HTTP Request - "Data A"
        While Controller
                CSV Data Set Config - data-b.csv
                HTTP Request - "Data B"

All the links in Data A are processed, and the results look good, but
nothing is ever run in Data B.

Thanks,

Mark