A stream application uses small chunks of executable code configured to process data tuples flowing into a processing element. A scheduler allocates the processing elements to individual compute nodes or hosts for execution. However, the stream application may assign various constraints that stipulate which hosts are suitable for a particular processing element. If a host meets the constraints, it may be categorized as an unconditional candidate host. In addition, the scheduler may also track conditional candidate hosts that would be suitable for the processing element if a certain user action is performed—e.g., modifying a constraint, removing a constraint, modifying a stream element, and the like. The list of conditional candidate hosts may then be displayed to the user who can choose to perform the one or more actions to change the conditional candidate host to an unconditional candidate host for the processing element.