Recurse Center Day 6: Raft's Safety Argument and Cryptopals Round 2
I also re-read some parts of the Raft paper, specifically focusing on the the arguments that support Raft's safety guarantee -- the guarantee that it if any server has applied a log entry to its state machine, then no other server may apply a different command at that same log index.
As I understand it, the guarantee hinges on these three requirements:
- Instructions to commit a log move in one direction only: from leaders to followers.
- A Follower will never vote for a Candidate if its own log is more up-to-date than the Candidate's, which, in conjunction with a few other things, gives the guarantee that a Leader's log will always contain all committed log entries.
- Log entries must not be overwritten.
So if the Leader is the only participant that can commit new log entries and the Leader must have an up-to-date log, then there's no way that a new Leader's state machine can be out-of-date or instruct other servers to overwrite old entries with invalid entries. Cool!
I also started re-implementing my cryptopals solutions in Python. Last time I wrote them in Go, but I don't write much Go nowadays and I think it's worth my time to practice Python since it's a such a widely-used language. I'm excited to revisit the challenges and hopefully write some much prettier code. Looking at my old solutions yesterday had me like...