ยง 1001. Necessary joinder of parties. (a) Parties who should be joined. Persons who ought to be parties if complete relief is to be accorded between the persons who are parties to the action or who might be inequitably affected by a judgment in the action shall be made plaintiffs or defendants. When a person who should join as a plaintiff refuses to do so he may be made a defendant. (b) When joinder excused. When a person who should be joined under subdivision (a) has not been made a party and is subject to the jurisdiction of the court, the court shall order him summoned. If jurisdiction over him can be obtained only by his consent or appearance, the court, when justice requires, may allow the action to proceed without his being made a party. In determining whether to allow the action to proceed, the court shall consider: 1. whether the plaintiff has another effective remedy in case the action is dismissed on account of the nonjoinder; 2. the prejudice which may accrue from the nonjoinder to the defendant or to the person not joined; 3. whether and by whom prejudice might have been avoided or may in the future be avoided; 4. the feasibility of a protective provision by order of the court or in the judgment; and 5. whether an effective judgment may be rendered in the absence of the person who is not joined.