Scalable causal message logging for wide‐area environments
Karan Bhatia, Keith Marzullo, Lorenzo Alvisi · Concurrency and Computation Practice and Experience · 2003
Abstract Wide‐area systems are gaining in popularity as an infrastructure for running scientific applications. From a fault tolerance perspective, these environments are challenging because of their scale and their variability. Causal message logging protocols have attractive properties that make them suitable for these environments. They spread fault tolerance information around in the system providing high availability. This information can also be used to replicate objects that are otherwise inaccessible because of network partitions. However, current causal message logging protocols do not scale to thousands or millions of processes. We describe the Hierarchical Causal Message Logging Protocol (HCML) that uses a hierarchy of shared logging sites, or proxies, to significantly reduce the space requirements as compared with existing protocols. These proxies also act as caches for fault tolerance information and reduce the overall message overhead by as much as 50%. HCML also leverages differences in bandwidth between processes that reduces overall message latency by as much as 97%. Copyright © 2003 John Wiley & Sons, Ltd.