e8e4456ec7
This draft extends and obsoletes #8123 by introducing a way of determining the workload type from service level parameters, and then using this context to qualify requests for shedding. The rough idea is that when the admission queue in the CQL server is hit, it might make more sense to start shedding surplus requests instead of accumulating them on the semaphore. The assumption that interactive workloads are more interested in the success rate of as many requests as possible, and hanging on a semaphore reduces the chances for a request to succeed. Thus, it may make sense to shed some requests to reduce the load on this coordinator and let the existing requests to finish. It's a draft, because I only performed local guided tests. #8123 was followed by some experiments on a multinode cluster which I want to rerun first. Closes #8680 * github.com:scylladb/scylla: test: add a case for conflicting workload types cql-pytest: add basic tests for service level workload types docs: describe workload types for service levels sys_dist_ks: fix redundant parsing in get_service_level sys_dist_ks: make get_service_level exception-safe transport: start shedding requests during potential overload client_state: hook workload type from service levels cql3: add listing service level workload type cql3: add persisting service level workload type qos: add workload_type service level parameter
Single-node funtional tests for Scylla's CQL features. Tests use the Python CQL library and the pytest frameworks. By using an actual CQL library for the tests, they can be run against any implementation of CQL - both Scylla and Cassandra. Most tests - except in rare cases - should pass on both, to ensure that Scylla is compatible with Cassandra in most features.
To run all tests against an already-running local installation of Scylla
or Cassandra on localhost, just run pytest. The "--host" and "--port"
can be used to give a different location for the running Scylla or Cassanra.
More conveniently, we have two scripts - "run" and "run-cassandra" - which do all the work necessary to start Scylla or Cassandra (respectively), and run the tests on them. The Scylla or Cassandra process is run in a temporary directory which is automatically deleted when the test ends.
Additional options can be passed to "pytest" or to "run" / "run-cassandra" to control which tests to run:
- To run all tests in a single file, do
pytest test_table.py. - To run a single specific test, do
pytest test_table.py::test_create_table_unsupported_names.
Additional useful pytest options, especially useful for debugging tests:
- -v: show the names of each individual test running instead of just dots.
- -s: show the full output of running tests (by default, pytest captures the test's output and only displays it if a test fails)