Abstract: A group communication system (GCS), for use within a group of clustered computing nodes, provides a flexible group membership model. Flexible group members are defined generally as physical computing entities (such as computing nodes or other devices) or logical computing entities that take part in a distributed application. Such logical entities may include substantially any combination of processes, threads and callback functions. Logical entities that are members in the group may also be objects, such as files, that at least at some times during their existence have no active processes or threads. A single member may include multiple simultaneous processes.

Abstract: A method for controlling operation of a computer software application running on a plurality of computing entities, which are members of a group of mutually-linked computing entities running the application within a distributed computing system. The method includes receiving an indication of a change in membership of the group together with a reason for the change. A membership change message is delivered to the members, so as to inform the members of the change and of the reason for the change.

Abstract: A method for distributing messages among a group of member computing entities, which are mutually-linked in a distributed computing system. The members communicate in accordance with a communication protocol, which delivers a sequence of full-group multicast messages to all of the members in the group in an order that is uniform among all of the members. A sub-group is defined from among the members in the group, and a sub-group message is distributed to the members in the sub-group, such that the sub-group message is delivered to all of the sub-ground members in a uniform position with respect to the order of the full-group multicast messages, as well as with respect to other sub-group messages.

Abstract: A method for controlling operation of a computer software application running on a given computing entity, which is a member of a group of mutually-linked computing entities running the application within a distributed computing system. The method includes selecting a partitioning strategy for the application from among a plurality of available strategies. When a message is received at the given computing entity indicative of a change in membership of the group, the given computing entity determines in accordance with the selected partitioning strategy whether the given computing entity belongs to a primary component of the group following the change in membership, such that running of the software application on the given entity is restricted if the entity does not belong to the primary component.