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README.md

jepsen.hazelcast

A Jepsen test suite for Hazelcast IMDG.

How to Use

We run the Jepsen tests using docker containers for convenience.

First, make sure that Docker is installed. To start Jepsen containers, execute the following command in jepsen directory which is one level up from hazelcast directory:

$ cd docker && ./up.sh

Our Jepsen tests are ready to go once all containers are up and running fine. You can get into the jepsen-control container by executing the following command:

$ docker exec -it jepsen-control bash

Then, while you are inside the jepsen-control container, run the following command:

$ cd hazelcast

While you are at the hazelcast directory, you can run our Jepsen tests using lein. For instance, lein run test --workload non-reentrant-cp-lock --time-limit 120 runs the non-reentrant lock test for 120 seconds.

You can also use the repeat scripts to run tests multiple times. For instance, while in the hazelcast directory, run sh repeat_single_test.sh non-reentrant-cp-lock 5 120 to run the non-reentrant CP lock test 5 times, each test taking 120 seconds, or run sh repeat_all_cp_tests.sh 5 120 to run the whole CP subsystem test suite 5 times, each test taking 120 seconds. These scripts stop on a test failure so that you can report and investigate the failure.

Test Cases

With Hazelcast version 3.12, we released our Jepsen test suite for the CP data structures. Besides the new CP subsystem test suite, there are other tests written by Kyle Kingsbury to test AP data structures in Hazelcast.

Our CP subsystem test suite is as follows:

  • Non-reentrant lock (--workload non-reentrant-cp-lock): In this test case, we test if the new FencedLock data structure behaves as a non-reentrant mutex, i.e., it can be held by a single endpoint at a time and only the lock holder endpoint can release it. Moreover, the lock cannot be acquired by the same endpoint reentrantly. It means that while a client holds the lock, it cannot acquire the lock again, without releasing the lock first.

  • Reentrant lock (--workload reentrant-cp-lock): We test if the new FencedLock data structure behaves as a reentrant mutex. The lock instance can be held by a single endpoint at a time and only the lock holder endpoint can release it. Moreover, the current lock holder can reentrantly acquire the lock one more time. Reentrant lock acquire limit is 2 for this test.

  • Non-reentrant fenced lock (--workload non-reentrant-fenced-lock): FencedLock orders lock holders by a monotonic fencing token, which is incremented each time the lock switches from the free state to the held state. In this test case, we validate monotonicity of fencing tokens assigned to subsequent lock holders. Moreover, the lock cannot be acquired by the same endpoint reentrantly. It means that while a client holds the lock, it cannot acquire the lock again, without releasing the lock first.

  • Reentrant fenced lock (--workload reentrant-fenced-lock): FencedLock orders lock holders by a monotonic fencing token, which is incremented each time the lock switches from the free state to the held state. However, if the current lock holder acquires the lock reentrantly, it will get the same fencing token. Reentrant lock acquire limit is 2 for this test.

  • Semaphore (--workload semaphore): In this test, we initialize our new linearizable ISemaphore with 2 permits. Each client acquires and releases a permit in a loop and we validate permits are held by at most 2 clients at a time.

  • Unique ID Generation with the new linearizable IAtomicLong (--workload cp-id-gen-long): In this test, each client generates a unique long id by using a linearizable IAtomicLong instance and we validate uniqueness of generated ids.

  • Compare-and-swap Register with the new linearizable IAtomicLong (--workload cp-cas-long): In this test, clients randomly perform write and compare-and-swap operations.

  • Compare-and-swap Register with the new linearizable IAtomicReference (--workload cp-cas-reference): In this test, clients randomly perform write and compare-and-swap operations.

In each test, multiple clients send concurrent operations to a shared data structure, which is replicated to the Hazelcast cluster. In the mean time, Jepsen's nemesis injects network partitions into the system. At the end of the test, Jepsen validates if the history of operations is linearizable. We are planning to add more failure modes in future.

License

Original work Copyright © 2015-2019, Jepsen, LLC

Modified work Copyright © 2019, Hazelcast, Inc. All Rights Reserved.

Distributed under the Eclipse Public License version 1.0 or (at your option) any later version.

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