1. A method comprising the following steps: determining, within a datacenter, one or more dimensions of a set of containers in which multiple tasks associated with a request are to be executed, wherein the datacenter comprises: multiple processing nodes and multiple platforms, wherein the multiple platforms comprise multiple software entities which compete for one or more resources of the processing nodes in the datacenter, and wherein the set of containers comprises multiple software containers within the processing nodes of the datacenter, wherein each of the containers comprises an allocation of a given fraction of each of the one or more resources of the processing node to which each of the containers is assigned; assigning each container in the set of containers (i) to one of the processing nodes on one of the multiple platforms based on the determined one or more dimensions of the container being assigned, and (ii) to a platform owner selected from owners of the multiple platforms based on a comparison of one or more resource requirements attributed to each of the multiple platforms and the determined one or more dimensions of the container; and generating container assignments across the set of containers for the multiple tasks associated with the request, wherein said generating comprises incorporating (i) the assigned node of each container in the set of containers, (ii) the assigned platform owner of each container in the set of containers, (iii) one or more scheduling requirements of each of the multiple platforms, wherein said one or more scheduling requirements comprises one or more parameters for implementing preemption of a container from a given sharing platform, and wherein the one or more parameters for implementing preemption of a container comprises ownership identification of the container, and (iv) one or more utilization objectives comprising at least long-term fairness across the multiple platforms, wherein the long-term fairness (a) increases use of resources across the multiple platforms, and (b) facilitates sharing of resources across the multiple platforms to a predetermined extent embodied via a sharing guarantee of each of the multiple platforms, wherein said sharing guarantee of each of the multiple platforms comprises a self-appointed status representing each given platform's degree of willingness to share containers with one or more additional platforms, wherein the degree includes a self-appointed quantity of one or more containers; wherein said steps are carried out by at least one computing device.