Hi everyone! Currently we have a good set of unit tests for our IO Transforms - those tend to run against in-memory versions of the data stores. However, we'd like to further increase our test coverage to include running them against real instances of the data stores that the IO Transforms work against (e.g. cassandra, mongodb, kafka, etc…), which means we'll need to have real instances of various data stores.
Additionally, if we want to do performance regression detection, it's important to have instances of the services that behave realistically, which isn't true of in-memory or dev versions of the services. Proposed solution ------------------------- If we accept this proposal, we would create an infrastructure for running real instances of data stores inside of containers, using container management software like mesos/marathon, kubernetes, docker swarm, etc… to manage the instances. This would enable us to build integration tests that run against those real instances and performance tests that run against those real instances (like those that Jason Kuster is proposing elsewhere.) Why do we need one centralized set of instances vs just having various people host their own instances? ------------------------- Reducing flakiness of tests is key. By not having dependencies from the core project on external services/instances of data stores we have guaranteed access to the services and the group can fix issues that arise. An exception would be something that has an ops team supporting it (eg, AWS, Google Cloud or other professionally managed service) - those we trust will be stable. There may be a lot of different data stores needed - how will we maintain them? ------------------------- It will take work above and beyond that of a normal set of unit tests to build and maintain integration/performance tests & their data store instances. Setup & maintenance of the data store containers and data store instances on it must be automated. It also has to be as simple of a setup as possible, and we should avoid hand tweaking the containers - expecting checked in scripts/dockerfiles is key. Aligned with the community ownership approach of Apache, as members of the community are excited to contribute & maintain those tests and the integration/performance tests, people will be able to step up and do that. If there is no longer support for maintaining a particular set of integration & performance tests and their data store instances, then we can disable those tests. We may document on the website what IO Transforms have current integration/performance tests so users know what level of testing the various IO Transforms have. What about requirements for the container management software itself? ------------------------- * We should have the data store instances themselves in Docker. Docker allows new instances to be spun up in a quick, reproducible way and is fairly platform independent. It has wide support from a variety of different container management services. * As little admin work required as possible. Crashing instances should be restarted, setup should be simple, everything possible should be scripted/scriptable. * Logs and test output should be on a publicly available website, without needing to log into test execution machine. Centralized capture of monitoring info/logs from instances running in the containers would support this. Ideally, this would just be supported by the container software out of the box. * It'd be useful to have good persistent volume in the container management software so that databases don't have to reload large data sets every time. * The containers may be a place to execute runners themselves if we need larger runner instances, so it should play well with Spark, Flink, etc… As I discussed earlier on the mailing list, it looks like hosting docker containers on kubernetes, docker swarm or mesos+marathon would be a good solution. Thanks, Stephen Sisk
