We propose a simple all-optical diode which is comprised of an asymmetric ring cavity containing a two-level atomic ensemble. Attributed to spatial symmetry breaking of the ring cavity, direction-dependent optical bistability is obtained in a classical bistable system. Therefore, a giant optical non-reciprocity is generated, which guarantees an all-optical diode with a high contrast up to 22 d B. Furthermore, its application as an all-optical logic AND gate is also discussed. We propose a simple all-optical diode which is comprised of an asymmetric ring cavity containing a two-level atomic ensemble. As a result, direction-dependent optical bistability is obtained in a classical bistable system. Thus, a giant optical non-reciprocity is generated, which guarantees an all-optical diode with a high contrast up to 22 d B. Furthermore, its application as an all-optical logic AND gate is also discussed.