PDL Abstract

There Is More Consensus in Egalitarian Parliaments

Proceedings of the 24th ACM Symposium on Operating Systems Principles (SOSP'13), November 3-6, 2013, Nemacolin Woodlands Resort, Farmington, PA.

Iulian Moraru, David G. Andersen & Michael Kaminsky^

Carnegie Mellon University
^Intel Labs


This paper describes the design and implementation of Egalitarian Paxos (EPaxos), a new distributed consensus algorithm based on Paxos. EPaxos achieves three goals: (1) optimal commit latency in the wide-area when tolerating one and two failures, under realistic conditions; (2) uniform load balancing across all replicas (thus achieving high throughput); and (3) graceful performance degradation when replicas are slow or crash.

Egalitarian Paxos is to our knowledge the first protocol to achieve the previously stated goals efficiently—that is, requiring only a simple majority of replicas to be nonfaulty, using a number of messages linear in the number of replicas to choose a command, and committing commands after just one communication round (one round trip) in the common case or after at most two rounds in any case. We prove Egalitarian Paxos's properties theoretically and demonstrate its advantages empirically through an implementation running on Amazon EC2.