What are the pros and cons of using broadcast variables in a singleton?

Question

As I understand it, broadcast variables are created once, but used many times. So it occurs to me that I should create a broadcast variable inside a singleton class, is this a bad idea? What are the pros and cons of using a singleton class to hold the broadcast variable?

Answer 1

I think Broadcast variables deserve some explanations in order to better understand how this mechanism works:

A Broadcast variable allows to keep a read-only variable cached on each machine rather than shipping a copy of it with tasks. It can be used, for example, to give every node a copy of a large input dataset in an efficient manner.
You can check further details at: Spark Broadcast variables

After you create a broadcast variable in Spark, you get a wrapper around v (accessed by calling broadcastVar.value()), so using a singleton will be using a singleton reference for the wrapper, rather than the actual value and so, the singleton pattern may have much less impact either way.
You could also use the same wrapper reference throughout the entire life-cycle of your Spark execution.

As this is a reference to a read-only variable, those options will present a similar behavior.