pro per plaintiff asks: scheduled for a motion to compel discovery by one of two defendants. If I file Disissal of that one defendant does that cancel

Yes, but... If you dismiss one defendant without obtaining a signed waiver of costs, that defendant will be the "prevailing party" and be entitled to recover its "costs of suit." In addition to filing fees and other expenses, if either a contract or a statute allows the prevailing party in this lawsuit to recover reimbursement for its attorney fees, then you also will be liable for such reimbursement. Giving up a defendant just to avoid some hard work responding to discovery is always a bad decision. The other defendant will be able to point to the other defendant as the real bad guy, as a defense. The defendant you dismiss might even confess that it was  the real bad guy, and provide the other defendant with a complete defense.  Litigation is very complicated and dfficult. Even licensed, trained, experienced lawyers make mistakes all the time. You really need an experienced and qualified attorney. Hire an attorney, instead of dismissing any defendant. Dana Sack