cassandra-stress CI

[muzarski]

Motivation

Core logic of cassandra-stress frontend has already been implemented, but there are no tests verifying the correctness of our solution.

This PR introduces two tests written in python which test runtime logic of cql-stress-cassandra-stress tool.

Changes

• fixed shebang in existing tools/test_with_scylla.py python script
• introduced docker/scylla_test/compose.yml docker-compose yaml defining a scylla node used during the tests
• extracted ScyllaDockerNode, as well as the logic corresponding to this type, to tools/util/scylla_docker.py
• scylla_docker function now makes use of docker compose to set up the container. Thanks to docker-compose up --wait flag, we can get rid of part of the code responsible for polling the scylla container until it's healthy.
• introduced tools/util/cassandra_stress.py which defines set of utility functions when working with cassandra-stress
• introduced two tests in tools directory. Included these tests in CI
• updated README.md

[muzarski]

v2: Rebased on top of master. Fixed review comments, including:

• changed cassandra pulling logic, so it skips the download phase if cassandra is already installed (caching)
• moved all of the C-S frontend CI test cases to ./tools/cassandra-stress-ci.sh, so the developers may easily simulate the CI run
• included instructions regarding cassandra-stress-ci.sh in README.md

[muzarski]

v3

Changes

• applied PEP-8 formatting to all of the python scripts
• replaced harcdoded keyspaces names with a generated ones
• changed the logic so we don't drop the keyspaces after the tests
• Introduced CqlStressCassandraStress class. It inherits from CSCliRunner along with CassandraStress
• added cassandra-download directory to .gitignore.
• log grouping prints in ./tools/cassandra-stress-ci.sh are now printed only in the GH actions environment (when CI env variable is set).

Notice

We still don't make use of the pytest framework. I need to get familiar with the framework, but don't want to delay the review process of the things that are already fixed.

[muzarski]

v4: rebased on top of master

[muzarski]

v5: using pytest to define test-cases

[muzarski]

v6:

• removed main functions from test_cs_* scripts, as test cases can be defined with pytest. Previous solution was a bit confusing since it let the user run the test using both CLI and pytest. We decided to be more consistent and be able to define test cases using only pytest.
• introduced pytest.fixtures next to test cases so we can bind test arguments to test functions
• renamed TestKeyspaces to Keyspaces since pytest might consider it as a test class (when it's a pure utility class)
• introduced CSCliRuntimeArguments structure to define workload size and concurrency. It's useful when defining new test cases which do not use the default runtime arguments (workload_size=100, concurrency=1).