Self-stabilizing Reconfiguration

Abstract

Current reconfiguration techniques depend on starting the system in a consistent configuration, in which all participating entities are in a predefined state. Starting from that state, the system must preserve consistency as long as a predefined churn rate of processors joins and leaves is not violated, and unbounded storage is available. Many systems cannot control this churn rate and lack access to unbounded storage. System designers that neglect the outcome of violating the above assumptions may doom the system to exhibit illegal behaviors. We present the first automatically recovering reconfiguration scheme that recovers from transient faults, such as temporal violations of the above assumptions. Our self-stabilizing solutions regain safety automatically by assuming temporal access to reliable failure detectors (FDs). Once safety is established, the FD reliability is no longer needed. Still, liveness is conditioned by the FD’s unreliable signals. Our self-stabilizing reconfiguration techniques can serve as the basis for the implementation of several dynamic services over message passing systems. Examples include self-stabilizing reconfigurable virtual synchrony, extendable to a self-stabilizing reconfigurable state machine replication.