Conditional branching during pipeline execution time

[Praveen K Viswanathan]

Hello Everyone,

Apache Beam allows conditional branching during pipeline construction time,
but I have to decide whether to execute DoFn A or DoFn B during run time
(based upon a PCollection flag).

My DoFns A and B are inside a custom transformation class and I am passing
my flag as PCollectionView to the transformation class. However, Beam does
not wait for the actual value of the PCollectionView and decides which DoFn
to call during DAG preparation itself (always goes to else part)

class CustomTx {
   public CustomTx(flag) {
    this.flag = flag;
   }

 public expand {
  if (flag)
     DoFn A
  else
     DoFn B
  }
}

class DoFn A {
}

class DoFn B {
}

If I have a DoFn inside my transformation's expand method and pass the flag
as side input it gives the correct value but then, I cannot call a DoFn
inside a DoFn. Appreciate any pointers on the best way to approach this
branching case.

-- 
Thanks,
Praveen K Viswanathan