Cal. Civ. Proc. Code § 877.6
(a)
(e) When a determination of the good faith or lack of good faith of a settlement is made, any party aggrieved by the determination may petition the proper court to review the determination by writ of mandate. The petition for writ of mandate shall be filed within 20 days after service of written notice of the determination, or within any additional time not exceeding 20 days as the trial court may allow.