When can a party ask for rescission of a contract because the other party failed to perform, under the Civil Code?

A party to a bilateral contract may seek rescission after the defaulting party has been put in default. The non-defaulting party may instead seek performance; damages may accompany either remedy where justified. 1

The court may grant the debtor additional time or refuse rescission if the unperformed part is of little importance in relation to the obligation as a whole. 1