--- layout: docs page_title: Jepsen Testing description: >- Jepsen is a tool, written by Kyle Kingsbury, designed to test the partition tolerance of distributed systems. It creates network partitions while fuzzing the system with random operations. The results are analyzed to see if the system violates any of the consistency properties it claims to have. --- # Jepsen Testing [Jepsen](http://aphyr.com/posts/281-call-me-maybe-carly-rae-jepsen-and-the-perils-of-network-partitions) is a tool, written by Kyle Kingsbury, designed to test the partition tolerance of distributed systems. It creates network partitions while fuzzing the system with random operations. The results are analyzed to see if the system violates any of the consistency properties it claims to have. As part of our Consul testing, we ran a Jepsen test to determine if any consistency issues could be uncovered. In our testing, Consul gracefully recovered from partitions without introducing any consistency issues. ## Running the tests At the moment, testing with Jepsen is rather complex as it requires setting up multiple virtual machines, SSH keys, DNS configuration, and a working Clojure environment. We hope to contribute our Consul testing code upstream and to provide a Vagrant environment for Jepsen testing soon. ## Output Below is the output captured from Jepsen. We ran Jepsen multiple times, and it passed each time. This output is only representative of a single run and has been edited for length. Please reach out on [Consul's Discuss](https://discuss.hashicorp.com/c/consul) if you would like to reproduce the Jepsen results. ```shell-session $ lein test :only jepsen.system.consul-test lein test jepsen.system.consul-test INFO jepsen.os.debian - :n5 setting up debian INFO jepsen.os.debian - :n3 setting up debian INFO jepsen.os.debian - :n4 setting up debian INFO jepsen.os.debian - :n1 setting up debian INFO jepsen.os.debian - :n2 setting up debian INFO jepsen.os.debian - :n4 debian set up INFO jepsen.os.debian - :n5 debian set up INFO jepsen.os.debian - :n3 debian set up INFO jepsen.os.debian - :n1 debian set up INFO jepsen.os.debian - :n2 debian set up INFO jepsen.system.consul - :n1 consul nuked INFO jepsen.system.consul - :n4 consul nuked INFO jepsen.system.consul - :n5 consul nuked INFO jepsen.system.consul - :n3 consul nuked INFO jepsen.system.consul - :n2 consul nuked INFO jepsen.system.consul - Running nodes: {:n1 false, :n2 false, :n3 false, :n4 false, :n5 false} INFO jepsen.system.consul - :n2 consul nuked INFO jepsen.system.consul - :n3 consul nuked INFO jepsen.system.consul - :n4 consul nuked INFO jepsen.system.consul - :n5 consul nuked INFO jepsen.system.consul - :n1 consul nuked INFO jepsen.system.consul - :n1 starting consul INFO jepsen.system.consul - :n2 starting consul INFO jepsen.system.consul - :n4 starting consul INFO jepsen.system.consul - :n5 starting consul INFO jepsen.system.consul - :n3 starting consul INFO jepsen.system.consul - :n3 consul ready INFO jepsen.system.consul - :n2 consul ready INFO jepsen.system.consul - Running nodes: {:n1 true, :n2 true, :n3 true, :n4 true, :n5 true} INFO jepsen.system.consul - :n5 consul ready INFO jepsen.system.consul - :n1 consul ready INFO jepsen.system.consul - :n4 consul ready INFO jepsen.core - Worker 0 starting INFO jepsen.core - Worker 2 starting INFO jepsen.core - Worker 1 starting INFO jepsen.core - Worker 3 starting INFO jepsen.core - Worker 4 starting INFO jepsen.util - 2 :invoke :read nil INFO jepsen.util - 3 :invoke :cas [4 4] INFO jepsen.util - 0 :invoke :write 4 INFO jepsen.util - 1 :invoke :write 1 INFO jepsen.util - 4 :invoke :cas [4 0] INFO jepsen.util - 2 :ok :read nil INFO jepsen.util - 4 :fail :cas [4 0] (Log Truncated...) INFO jepsen.util - 4 :invoke :cas [3 3] INFO jepsen.util - 4 :fail :cas [3 3] INFO jepsen.util - :nemesis :info :stop nil INFO jepsen.util - :nemesis :info :stop "fully connected" INFO jepsen.util - 0 :fail :read nil INFO jepsen.util - 1 :fail :write 0 INFO jepsen.util - :nemesis :info :stop nil INFO jepsen.util - :nemesis :info :stop "fully connected" INFO jepsen.core - nemesis done INFO jepsen.core - Worker 3 done INFO jepsen.util - 1 :invoke :read nil INFO jepsen.core - Worker 2 done INFO jepsen.core - Worker 4 done INFO jepsen.core - Worker 0 done INFO jepsen.util - 1 :ok :read 3 INFO jepsen.core - Worker 1 done INFO jepsen.core - Run complete, writing INFO jepsen.core - Analyzing (Log Truncated...) INFO jepsen.core - Analysis complete INFO jepsen.system.consul - :n3 consul nuked INFO jepsen.system.consul - :n2 consul nuked INFO jepsen.system.consul - :n4 consul nuked INFO jepsen.system.consul - :n1 consul nuked INFO jepsen.system.consul - :n5 consul nuked 1964 element history linearizable. :D Ran 1 tests containing 1 assertions. 0 failures, 0 errors. ```