"We might get outputs that are arbitrarily wrong, up to and including breaking program invariants"

"The outputs might never converge to correctness"

Giving a short talk on Jepsen at LADIS this afternoon! Our session starts at 14:45 US Eastern.

Live stream:

New release! Maelstrom 0.2.0 is a workbench for learning distributed systems by writing your own, in any language. Comes with a six-chapter tutorial in writing your own toy echo, gossip, CRDT, Datomic, and Raft systems. Powered by Jepsen and Elle!

New Jepsen release: 0.2.3. Super small, just a few bugfixes and performance improvements. Enjoy!

Howdy guys, gals, and non-binary pals! Jepsen 0.2.2 is now available, with a slew of minor bugfixes, performance improvements, and new utility functions. Look out for a change to multi-fault nemesis scheduling:

RT @asatarin
"Cobra: Making Transactional Key-Value Stores Verifiably Serializable"

Given black box trace of KV transactions determine if observed behaviors are serializable at scale (10K transactions)

New report: we worked with @ScyllaDB to identify and fix cases of LWT split-brain in healthy clusters due to improper hashing and membership changes, as well as documentation improvements. Notably, Scylla no longer claims non-LWT isolation!

@rior Thanks! I'm not sure yet, I hope so though. :-)

RT @yow_conf
Can you believe it?! We're adding ONE more speaker to and it's @aphyr!

We trust databases to store our data, but should we? Learn the basics of distributed systems testing & advice for testing your own systems in his keynote - Jepsen 13.

RT @adriancolyer
"Elle: inferring isolation anomalies from experimental observations", Kingsbury & Alvaro, VLDB'20.

Be afraid databases, be very afraid: Jepsen just got a whole lot more powerful...

Jepsen's AWS Marketplace product (launches a whole Jepsen cluster in a few clicks) has been updated for Debian Buster, and now includes additional dependencies you'll want for running tests based on Elle. Happy testing!

@rior 20% of the time, it's isolated 100% of the time

Put a bunch of work into the Jepsen docker-compose setup, and I'm pleased to report it now gives you a full Debian Buster cluster with keys and dependencies out of the box--should be good for running the latest tests. Hopefully this helps!

Do you use Cassandra or another CQL-compatible database? I'd like to hear your perspective on adding things to a CQL set:

A bug in Jepsen: from versions 0.1.2 to 0.2.0, the counter checker docstring incorrectly claimed to handle decrements, which could cause valid histories to be reported as failures. This did not affect official Jepsen reports, but other counter tests using decrements may have been affected:

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