raft -- raft -- raft your boat, gently down the consensus stream

Brandon Callender bmcallender@uchicago.edu Tasnim Rahman rahmant@uchicago.edu Anthony Crespo acrespo@uchicago.edu

To run:

• cd impl
• chmod a+x install-mvn.sh
• ./install-mvn.sh
• source ~/.bashrc
• mvn install
• cd target
• run chistributed

Work Division -- Initial split:

Brandon: ZMQ, requestVote, requestVote Response, Stable storage database management, JSON/message handling scaffolding Anthony: AppendEntries, AppendEntriesResponse, log/commit logic/management Tasnim: State Transition management, client GET/SET state data management

but then...

ALL: Debugging, Refactoring/Fixing major architectural flaws that became evident.

Caveats

• Occasionally, the -- --force-leader and -- --force role commands will not result in the selected node staying the leader -- another node might time out waiting on a heartbeat from the leader node if it is spawned by chistributed at an awkward time window.

• There is a narrow window in which if a leader is partitioned/failed after committing a value but before telling the other nodes its been committed, when the new leader is elected, it may send out a duplicate set response -- this doesn't effect safety, it will never fail a commit a leader has already said was committed, but is technically a flaw