Allocating host for instances with anti affinity rule with adaptable sharing to allow instances associated with different failure domains to share surviving hosts

A non-transitory computer readable recording medium storing a computer program product for managing a communications network by allocating hosts for virtual network function instances of a virtual network function component, the computer program product comprising software instructions which, when run on processing circuitry of an apparatus, causes the apparatus to:

• receive a request to allocate instances to be shared by a virtual network function component;
• obtain, from the request, a number N indicating a minimum number of the instances that are required, and a number M indicating how many additional ones of the instances are to be allocated;
• responsive to the request, provide an indication of a maximum number of the instances to be allocated to one of the hosts, wherein the maximum number of the instances is determined by automatically deriving at least one of the maximum number according to a specified number of instances still available after loss of at least one host, the maximum number according to a specified total number of hosts, or the maximum number according to a specified fault tolerance in terms of how many of the allocated hosts can be lost while still leaving sufficient hosts that the virtual network function component can still be shared across at least N of the instances;
• and
• responsive to the request requesting that the allocation of the instances be to different ones of the hosts and if the sharing of the instances by the virtual network function component can be adapted in the event of unavailability of any of the allocated instances, allocate automatically N+M of the instances to less than N+
• M of the hosts across a plurality of separate failure domains based on the maximum number of instances.

An apparatus for managing a communications network by allocating hosts for virtual network function instances of a virtual network function component, the apparatus comprising:

• processing circuitry;
• memory containing instructions executable by the processing circuitry whereby the apparatus is operative to:
• receive a request to allocate instances to be shared by a virtual network function component,
• obtain from the request a number N indicating a minimum number of the instances that are required, and a number M indicating how many additional ones of the instances are to be allocated;
• responsive to the request, provide an indication of a maximum number of the instances to be allocated to one of the hosts, wherein the maximum number of the instances is determined by automatically deriving at least one of the maximum number according to a specified number of instances still available after loss of at least one host, the maximum number according to a specified total number of hosts, or the maximum number according to a specified fault tolerance in terms of how many of the allocated hosts can be lost while still leaving sufficient hosts that the virtual network function component can still be shared across at least N of the instances;
• and
• responsive to the request requesting that the allocation of the instances be to different ones of the hosts, and if the sharing of the instances by the virtual network function component can be adapted in the event of unavailability of any of the allocated instances, allocate automatically N+M of the instances to less than N+M of the hosts across a plurality of separate failure domains based on the maximum number of instances.