Causality in a hierarchical group
K. Taguchi, Tomoya Enokido, Makoto Takizawa · 2003
In this paper we discuss a hierarchical group of processes to support hundreds of processes. Each subgroup has gateway processes which communicate with other subgroups. Processes and gateway processes in each subgroup are locally supported with causally ordered delivery of messages by some mechanism like vector clock. Even if messages are locally causally ordered in a subgroup, the messages may not be globally causally ordered in the group. We discuss how global causality of messages among a pair of processes is related with local causalities of the messages in subgroups. In addition, we present a protocol to causally deliver messages through subgroups that are hierarchically structured.