Knapsack, The K is silent

Knapsack splits tests across CI nodes and makes sure that tests will run comparable time on each node.

Parallel tests across CI server nodes based on each test file's time execution. Knapsack generates a test time execution report and uses it for future test runs.

Presentations about gem:

• X 2014 Kraków Ruby User Group
• VII 2014 Lunar Logic Dev Meeting

Sign up to get info about launch Knapsack Pro with more features and free access for beta users.

Without Knapsack

With Knapsack

Update gem

Please check changelog before update gem. Knapsack follows semantic versioning.

Installation

Add those lines to your application's Gemfile:

group :test, :development do
  gem 'knapsack'
end

And then execute:

$ bundle

Usage

Step for RSpec

Add at the beginning of your spec_helper.rb:

require 'knapsack'

# CUSTOM_CONFIG_GOES_HERE

Knapsack::Adapters::RspecAdapter.bind

Step for Cucumber

Create file features/support/knapsack.rb and add there:

require 'knapsack'

# CUSTOM_CONFIG_GOES_HERE

Knapsack::Adapters::CucumberAdapter.bind

Custom configuration

You can change default Knapsack configuration for RSpec or Cucumber tests. Here are examples what you can do. Put below configuration instead of CUSTOM_CONFIG_GOES_HERE.

Knapsack.tracker.config({
  enable_time_offset_warning: true,
  time_offset_in_seconds: 30
})

Knapsack.report.config({
  test_file_pattern: 'spec/**/*_spec.rb', # default value based on adapter
  report_path: 'knapsack_custom_report.json'
})

# you can use your own logger
require 'logger'
Knapsack.logger = Logger.new(STDOUT)
Knapsack.logger.level = Logger::INFO

Common step

Add this line at the bottom of Rakefile:

Knapsack.load_tasks if defined?(Knapsack)

Generate time execution report for your test files. Run below command on one of your CI nodes.

# Step for RSpec
$ KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

# Step for Cucumber
$ KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

Commit generated report knapsack_rspec_report.json or knapsack_cucumber_report.json into your repository.

This report should be updated only after you add a lot of new slow tests or you change existing ones which causes a big time execution difference between CI nodes. Either way, you will get time offset warning at the end of the rspec/cucumber results which reminds you when it’s a good time to regenerate the knapsack report.

Adding or removing tests

There is no need to regenerate the report every time when you add/remove test file. If you remove a test file then Knapsack will ignore its entry in report. In case when you add a new file and it doesn't already exist in report, the test file will be assigned to one of the CI node.

You'll want to regenerate your execution report whenever you remove or add a test file with a long time execution time that would affect one of the CI nodes. You will get Knapsack notification whenever is good time to regenerate report.

Setup your CI server

On your CI server run this command for the first CI node. Update CI_NODE_INDEX for the next one.

# Step for RSpec
$ CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:rspec

# Step for Cucumber
$ CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:cucumber

You can add KNAPSACK_TEST_FILE_PATTERN if your tests are not in default directory. For instance:

# Step for RSpec
$ KNAPSACK_TEST_FILE_PATTERN="directory_with_specs/**/*_spec.rb" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:rspec

# Step for Cucumber
$ KNAPSACK_TEST_FILE_PATTERN="directory_with_features/**/*.feature" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:cucumber

You can set KNAPSACK_REPORT_PATH if your knapsack report was saved in non default location. Example:

# Step for RSpec
$ KNAPSACK_REPORT_PATH="knapsack_custom_report.json" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:rspec

# Step for Cucumber
$ KNAPSACK_REPORT_PATH="knapsack_custom_report.json" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:cucumber

Info about ENV variables

CI_NODE_TOTAL - total number CI nodes you have.

CI_NODE_INDEX - index of current CI node starts from 0. Second CI node should have CI_NODE_INDEX=1.

Passing arguments to rspec

Knapsack allows you to pass arguments through to rspec. For example if you want to run only specs that have the tag focus. If you do this with rspec directly it would look like:

$ bundle exec rake rspec --tag focus

To do this with Knapsack you simply add your rspec arguments as parameters to the knapsack rake task.

$ bundle exec rake "knapsack:rspec[--tag focus]"

Remember that using tags to limit which specs get run will affect the time each file takes to run. One solution to this is to generate a new knapsack_rspec_report.json for the commonly run scenarios.

Passing arguments to cucumber

Add arguments to knapsack cucumber task like this:

$ bundle exec rake "knapsack:cucumber[--name feature]"

Info for CircleCI users

If you are using circleci.com you can omit CI_NODE_TOTAL and CI_NODE_INDEX. Knapsack will use CIRCLE_NODE_TOTAL and CIRCLE_NODE_INDEX provided by CircleCI.

Here is an example for test configuration in your circleci.yml file.

Step 1

For the first time run all tests on a single CI node with enabled report generator.

test:
  override:
    # Step for RSpec
    - KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

    # Step for Cucumber
    - KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

After tests pass on your CircleCI machine your should copy knapsack json report which is rendered at the end of rspec/cucumber results. Save it into your repository as knapsack_rspec_report.json or knapsack_cucumber_report.json file and commit.

Step 2

Now you should update test command and enable parallel. Please remember to add additional containers for your project in CircleCI settings.

test:
  override:
    # Step for RSpec
    - bundle exec rake knapsack:rspec:
        parallel: true # Caution: there are 8 spaces indentation!

    # Step for Cucumber
    - bundle exec rake knapsack:cucumber:
        parallel: true # Caution: there are 8 spaces indentation!

Now everything should works. You will get warning at the end of rspec/cucumber results if time execution will take too much.

Info for Travis users

Step 1

For the first time run all tests at once with enabled report generator. Edit .travis.yml

script:
  # Step for RSpec
  - "KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec"

  # Step for Cucumber
  - "KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features"

After tests pass your should copy knapsack json report which is rendered at the end of rspec/cucumber results. Save it into your repository as knapsack_rspec_report.json or knapsack_cucumber_report.json file and commit.

Step 2

You can parallel your builds across virtual machines with travis matrix feature. Edit .travis.yml

script:
  # Step for RSpec
  - "bundle exec rake knapsack:rspec"

  # Step for Cucumber
  - "bundle exec rake knapsack:cucumber"

env:
  - CI_NODE_TOTAL=2 CI_NODE_INDEX=0
  - CI_NODE_TOTAL=2 CI_NODE_INDEX=1

If you want to have some global ENVs and matrix of ENVs then do it like this:

script:
  # Step for RSpec
  - "bundle exec rake knapsack:rspec"

  # Step for Cucumber
  - "bundle exec rake knapsack:cucumber"

env:
  global:
    - RAILS_ENV=test
    - MY_GLOBAL_VAR=123
    - CI_NODE_TOTAL=2
  matrix:
    - CI_NODE_INDEX=0
    - CI_NODE_INDEX=1

Such configuration will generate matrix with 2 following ENV rows:

CI_NODE_TOTAL=2 CI_NODE_INDEX=0 RAILS_ENV=test MY_GLOBAL_VAR=123
CI_NODE_TOTAL=2 CI_NODE_INDEX=1 RAILS_ENV=test MY_GLOBAL_VAR=123

More info about global and matrix ENV configuration in travis docs.

Info for semaphoreapp.com users

Step 1

For the first time run all tests at once with enabled report generator. Set up your build command:

# Step for RSpec
KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

# Step for Cucumber
KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

After tests pass your should copy knapsack json report which is rendered at the end of rspec/cucumber results. Save it into your repository as knapsack_rspec_report.json or knapsack_cucumber_report.json file and commit.

Step 2

Knapsack supports semaphoreapp ENVs SEMAPHORE_THREAD_COUNT and SEMAPHORE_CURRENT_THREAD. The only thing you need to do is set up knapsack rspec/cucumber command for as many threads as you need. Here is an example:

# Thread 1
## Step for RSpec
bundle exec rake knapsack:rspec
## Step for Cucumber
bundle exec rake knapsack:cucumber

# Thread 2
## Step for RSpec
bundle exec rake knapsack:rspec
## Step for Cucumber
bundle exec rake knapsack:cucumber

Tests will be split across threads.

Gem tests

Spec

To run specs for Knapsack gem type:

$ bundle exec rspec spec

Spec examples

Directory spec_examples contains examples of fast and slow specs. There is a spec_example/spec_helper.rb with binded Knapsack.

To generate a new knapsack report for specs with focus tag (only specs in spec_examples/leftover directory have no focus tag), please type:

$ KNAPSACK_GENERATE_REPORT=true bundle exec rspec --default-path spec_examples --tag focus

Warning: Current knapsack_rspec_report.json file was generated for spec_examples except spec_examples/leftover directory. Just for testing reason to see how leftover specs will be distribute in a dumb way across CI nodes.

To see specs distributed for the first CI node type:

$ CI_NODE_TOTAL=2 CI_NODE_INDEX=0 KNAPSACK_SPEC_PATTERN="spec_examples/**/*_spec.rb" bundle exec rake knapsack:rspec

Specs in spec_examples/leftover take more than 3 seconds. This should cause a Knapsack time offset warning because we set time_offset_in_seconds to 3 in spec_examples/spec_helper.rb. Type below to see warning:

$ bundle exec rspec --default-path spec_examples

Cucumber examples

Here is a fork of Loomio Rails application with a lot of cucumber features and some rspec examples. Knapsack was added there - see code changes. Tests were splitted across a few machines on Travis CI - see builds.

Contributing

1. Fork it ( https://github.com/ArturT/knapsack/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Acknowledgements

Many thanks to Małgorzata Nowak for beautiful logo.

Mentions

• Lunar Logic Blog | Parallel your specs and don’t waste time
• Travis CI | Parallelizing RSpec and Cucumber on multiple VMs
• Semaphore | Running RSpec specs in parallel
• Semaphore | Running Cucumber scenarios in parallel