The Low Latency Fault Tolerance System

Abstract: The Low Latency Fault Tolerance (LLFT) system provides fault tolerance for distributed applications, using the leader-follower replication technique. The LLFT system provides application-transparent replication, with strong replica consistency, for applications that involve multiple interacting processes or threads. The LLFT system comprises a Low Latency Messaging Protocol, a Leader-Determined Membership Protocol, and a Virtual Determinizer Framework. The Low Latency Messaging Protocol provides reliable, totally ordered message delivery by employing a direct group-to-group multicast, where the message ordering is determined by the primary replica in the group. The Leader-Determined Membership Protocol provides reconfiguration and recovery when a replica becomes faulty and when a replica joins or leaves a group, where the membership of the group is determined by the primary replica. The Virtual Determinizer Framework captures the ordering information at the primary replica and enforces the same ordering at the backup replicas for major sources of non-determinism, including multi-threading, time-related operations and socket communication. The LLFT system achieves low latency message delivery during normal operation and low latency reconfiguration and recovery when a fault occurs.