Is this not reinventing part of Minion?

Depends on which part you mean. Minion is a good suggestion, but it also depends on the OP's requirements - if it's just a single task, then I think my code is good enough, but if OP needs to run more subprocesses then Minion's features would certainly be an advantage. However, AFAICT Minion doesn't support EventSource, which was a major point of my post.

Edit: Minor clarification.