Knapsack VS Parallel Tests

I've created a knapsack ruby gem for CI parallelisation that has over 122 million downloads. Primarily due to the fact, Gitlab is using it.

I spin off https://knapsackpro.com from the knapsack gem and we are helping our customers run fast CI builds.

name: Main on: [push] jobs: test: runs-on: ubuntu-latest # If you need DB like PostgreSQL, Redis then define service below. # https://github.com/actions/example-services/tree/master/.github/workflows services: postgres: image: postgres:10.8 env: POSTGRES_USER: postgres POSTGRES_PASSWORD: "" POSTGRES_DB: postgres ports: - 5432:5432 # needed because the postgres container does not provide a healthcheck # tmpfs makes DB faster by using RAM options: >- --mount type=tmpfs,destination=/var/lib/postgresql/data --health-cmd pg_isready --health-interval 10s --health-timeout 5s --health-retries 5 redis: image: redis ports: - 6379:6379 options: --entrypoint redis-server # https://help.github.com/en/articles/workflow-syntax-for-github-actions#jobsjob_idstrategymatrix strategy: fail-fast: false matrix: # [n] - where the n is a number of parallel jobs you want to run your tests on. # Use a higher number if you have slow tests to split them between more parallel jobs. # Remember to update the value of the `ci_node_index` below to (0..n-1). ci_node_total: [8] # Indexes for parallel jobs (starting from zero). # E.g. use [0, 1] for 2 parallel jobs, [0, 1, 2] for 3 parallel jobs, etc. ci_node_index: [0, 1, 2, 3, 4, 5, 6, 7] env: RAILS_ENV: test GEMFILE_RUBY_VERSION: 2.7.2 PGHOST: localhost PGUSER: postgres # Rails verifies the time zone in DB is the same as the time zone of the Rails app TZ: "Europe/Warsaw" steps: - uses: actions/checkout@v2 - name: Set up Ruby uses: ruby/setup-ruby@v1 with: # Not needed with a .ruby-version file ruby-version: 2.7 # runs 'bundle install' and caches installed gems automatically bundler-cache: true - name: Create DB run: | bin/rails db:prepare - name: Run tests env: KNAPSACK_PRO_TEST_SUITE_TOKEN_RSPEC: ${{ secrets.KNAPSACK_PRO_TEST_SUITE_TOKEN_RSPEC }} KNAPSACK_PRO_CI_NODE_TOTAL: ${{ matrix.ci_node_total }} KNAPSACK_PRO_CI_NODE_INDEX: ${{ matrix.ci_node_index }} KNAPSACK_PRO_LOG_LEVEL: info # if you use Knapsack Pro Queue Mode you must set below env variable # to be able to retry CI build and run previously recorded tests # https://github.com/KnapsackPro/knapsack_pro-ruby#knapsack_pro_fixed_queue_split-remember-queue-split-on-retry-ci-node KNAPSACK_PRO_FIXED_QUEUE_SPLIT: true # RSpec split test files by test examples feature - it's optional # https://knapsackpro.com/faq/question/how-to-split-slow-rspec-test-files-by-test-examples-by-individual-it KNAPSACK_PRO_RSPEC_SPLIT_BY_TEST_EXAMPLES: true run: | bundle exec rake knapsack_pro:queue:rspec

# Ruby CircleCI 2.0 configuration file # # Check https://circleci.com/docs/2.0/language-ruby/ for more details # version: 2 jobs: build: parallelism: 10 # https://circleci.com/docs/2.0/configuration-reference/#resource_class resource_class: small docker: # specify the version you desire here - image: circleci/ruby:2.7.1-node-browsers environment: PGHOST: 127.0.0.1 PGUSER: my_db_user RAILS_ENV: test # Split slow RSpec test files by test examples # https://knapsackpro.com/faq/question/how-to-split-slow-rspec-test-files-by-test-examples-by-individual-it KNAPSACK_PRO_RSPEC_SPLIT_BY_TEST_EXAMPLES: true # Specify service dependencies here if necessary # CircleCI maintains a library of pre-built images # documented at https://circleci.com/docs/2.0/circleci-images/ - image: circleci/postgres:10.6-alpine-ram environment: POSTGRES_DB: my_db_name POSTGRES_PASSWORD: "" POSTGRES_USER: my_db_user # Rails verifies Time Zone in DB is the same as time zone of the Rails app TZ: "Europe/Warsaw" - image: redis:6.0.7 working_directory: ~/repo environment: TZ: "Europe/Warsaw" steps: - checkout # Download and cache dependencies - restore_cache: keys: - v2-dependencies-bundler-{{ checksum "Gemfile.lock" }}-{{ checksum ".ruby-version" }} # fallback to using the latest cache if no exact match is found - v2-dependencies-bundler- - run: name: install ruby dependencies command: | bundle install --jobs=4 --retry=3 --path vendor/bundle - save_cache: paths: - ./vendor/bundle key: v2-dependencies-bundler-{{ checksum "Gemfile.lock" }}-{{ checksum ".ruby-version" }} # Database setup - run: bin/rails db:prepare - run: name: run tests command: | export CIRCLE_TEST_REPORTS=/tmp/test-results mkdir $CIRCLE_TEST_REPORTS bundle exec rake "knapsack_pro:queue:rspec[--format documentation --format RspecJunitFormatter --out tmp/rspec.xml]" # collect reports - store_test_results: path: /tmp/test-results - store_artifacts: path: /tmp/test-results destination: test-results

One, the interesting out-of-the-box solution is Knapsack Pro. It helps run your tests in a parallel efficient way.

Thanks for that feedback. For some more context, the container is designed to run 40+ processes in parallel sending remote instructions to AWS Device Farm for testing, so I suspect that the RAM usage is expected in this case. If you have any recommendations on re-architecting the execution here I'm all ears.

I know changing from RSpec to MiniTest requires some changes on how you organize the tests and how you think about writing them, but I found that I like MiniTest better after using it for more time, I think it goes straight to the point and it's better integrated (don't quote me on this, but I think minitest handles parallel tests better than RSpec in Rails app because that feature was added with mini test in mind, you would need to add an extra gem for rspec for that https://github.com/grosser/parallel_tests)

Several members of our team worked together to get the parallel_tests gem working for our codebase. Most of our tests were fine running in parallel, but we found enough that made assumptions about the order they would be run in that we had to do some fixing and rewriting. We kept this work in a feature branch, and kept chipping away at it until all the tests would pass.

Let's get one thing out of the way. If you use RSpec rather than Minitest, you are out of luck. RSpec does not support Rails 6 built-in parallel testing. There is an ongoing discussion about changing that, but there hasn't been any significant progress for a while. If you want parallel tests with RSpec, your best bet is still using third-party gems such as grosser/parallel_tests.