Brief Announcement: Design and Verification of a Logless Dynamic Reconfiguration Protocol in MongoDB Replication

Authors William Schultz, Siyuan Zhou, Stavros Tripakis

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Author Details

William Schultz
  • Northeastern University, Boston, MA, USA
Siyuan Zhou
  • MongoDB, New York, NY, USA
Stavros Tripakis
  • Northeastern University, Boston, MA, USA

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William Schultz, Siyuan Zhou, and Stavros Tripakis. Brief Announcement: Design and Verification of a Logless Dynamic Reconfiguration Protocol in MongoDB Replication. In 35th International Symposium on Distributed Computing (DISC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 209, pp. 61:1-61:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


We introduce a novel dynamic reconfiguration protocol for the MongoDB replication system that extends and generalizes the single server reconfiguration protocol of the Raft consensus algorithm. Our protocol decouples the processing of configuration changes from the main database operation log, which allows reconfigurations to proceed in cases when the main log is prevented from processing new operations. Additionally, this decoupling allows for configuration state to be managed by a logless replicated state machine, storing only the latest version of the configuration and avoiding the complexities of a log-based protocol. We present a formal specification of the protocol in TLA+, initial verification results of model checking its safety properties, and an experimental evaluation of how reconfigurations are able to quickly restore a system to healthy operation when node failures have stalled the main operation log. This announcement is a short version and the full paper is available at [Schultz et al., 2021].

Subject Classification

ACM Subject Classification
  • Information systems → Parallel and distributed DBMSs
  • Software and its engineering → Software verification
  • Reconfiguration
  • Consensus
  • State Machine Replication


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