Patching of virtual machines within sequential time windows

A computer program product, comprising a computer readable storage device having computer readable program code stored therein, said program code containing instructions executable by a processor of a computer system to implement a method, said method comprising:

• generating, by the processor, a patching schedule applicable for patching virtual machines in L redundancy groups,
• wherein said generating the patching schedule comprises scheduling, in W sequential time windows, P patches applicable to one or more virtual machines in the L redundancy groups, each redundancy group m (m=1, . . . , L) comprising Rm virtual machines, each redundancy group m (m=1, . . . , L) independently belonging to a respective software application x of X software applications, wherein P≥1, L≥1, Rm≥1, and X≥1, wherein the L redundancy groups collectively comprise at least 2 virtual machines,
• wherein said scheduling comprises determining, by the processor, xwmk for T tuples (w, m, k) defined by (w=1, . . . , W) and (m=1, . . . , L) and (k=1, . . . , Rm), by maximizing an objective function (F) subject to one or more constraints, wherein said determining xwmk comprises setting xwmk=1 if virtual machine k in redundancy group m is to be patched in time window w or setting xwmk=0 otherwise, and
• wherein the method further comprises patching, by the processor, the virtual machines in the L redundancy groups according to the patching schedule.

A computer system, comprising a processor, a memory coupled to the processor, and a computer readable storage device coupled to the processor, said storage device containing program code executable by the processor via the memory to implement a method, said method comprising:

• generating, by the processor, a patching schedule applicable for patching virtual machines in L redundancy groups,
• wherein said generating the patching schedule comprises scheduling, in W sequential time windows, P patches applicable to one or more virtual machines in the L redundancy groups, each redundancy group m (m=1, . . . , L) comprising Rm virtual machines, each redundancy group m (m=1, . . . , L) independently belonging to a respective software application x of X software applications, wherein P≥1, L≥1, Rm≥1, and X≥1, wherein the L redundancy groups collectively comprise at least 2 virtual machines,
• wherein said scheduling comprises determining, by the processor, xwmk for T tuples (w, m, k) defined by (w=1, . . . , W) and (m=1, . . . , L) and (k=1, . . . , Rm), by maximizing an objective function (F) subject to one or more constraints, wherein said determining xwmk comprises setting xwmk=1 if virtual machine k in redundancy group m is to be patched in time window w or setting xwmk=0 otherwise, and
• wherein the method further comprises patching, by the processor, the virtual machines in the L redundancy groups according to the patching schedule.