Tribute

Synod is named after a protocol, and the protocol has an author. This page says who he is, what he wrote, and why we chose the name.

The paper

In 1990 Leslie Lamport submitted a paper called "The Part-Time Parliament". It appeared in print in 1998, in ACM Transactions on Computer Systems (volume 16, issue 2, pages 133 to 169). It does not read like a usual systems paper. It tells the story of an invented parliament on Paxos, a Greek island, whose legislators wander in and out of the chamber, yet must still agree on one decree at a time and never contradict an earlier one.

Hidden in the story is a precise answer to a hard question: how can a group of machines that may crash, restart and lose messages still agree on a value? The paper calls its core algorithm the Synod protocol. Today most people call the whole family of ideas Paxos, and a great deal of the software that keeps data safe across many machines descends from it.

Why the name

A language for watching distributed systems think needed a name that stands for agreement under difficulty. The word synod means a council that meets to decide together, and it is the name Lamport gave to the heart of his algorithm. We took it as a thank-you and as a reminder of what the language is for: making that kind of reasoning something you can see.

The paxos example in the examples is the namesake algorithm written in Synod, so you can watch two proposers race and see why the chosen value never changes.

More from the same author

• "Paxos Made Simple" (ACM SIGACT News, 2001) explains the algorithm in plain prose, for readers who found the parliament story hard to follow.
• "Time, Clocks, and the Ordering of Events in a Distributed System" (Communications of the ACM, 1978) gave us the vocabulary of events, causality and logical time.
• TLA+ is his specification language for describing and checking systems before they are built.
• He received the 2013 ACM A.M. Turing Award, announced in March 2014, for fundamental contributions to the theory and practice of distributed and concurrent systems.

We are grateful for this work. If Synod makes one of its ideas easier to watch and understand, it has done its job.

References

1. Leslie Lamport. "The Part-Time Parliament". ACM Transactions on Computer Systems 16(2), May 1998, 133-169. ACM Digital Library.
2. Leslie Lamport. "Paxos Made Simple". ACM SIGACT News 32(4), December 2001, 51-58.
3. Leslie Lamport. "Time, Clocks, and the Ordering of Events in a Distributed System". Communications of the ACM 21(7), July 1978, 558-565.
4. Leslie Lamport's own page of his writings, where his papers can be read, with his notes on many of them.
5. ACM A.M. Turing Award 2013.