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Has anyone had any success trying to setup parallel tests on Heroku CI? Currently having issues with setting up the databases because Heroku ignores your database.yml

grosser/parallel_tests

Answer questions andacturkmen

Although this approach works perfectly, it doesn't make use of multiple CPUs in performance dynos and runs only a single process in each dyno. To be able to run multiple processes I took a different approach.

As others have mentioned, Heroku builds a default database and sets DATABASE_URL, which overrides your database.yml configuration. This causes errors in rake parallel:setup. So instead, I unset the DATABASE_URL and clone the default database in a bash script. Then I split the tests in according to number of CPUs and the number of dynos.

Here is my configuration:

// app.json
{
  ...
  "environments": {
    "test": {
      "formation": {
        "test": {
          "quantity": 4,
          "size": "performance-l"
        }
      },
      "env": {  "POSTGRESQL_VERSION": "11"  },
      "addons": ["heroku-postgresql:in-dyno", "heroku-redis:in-dyno"],
      "scripts": {
        "test": "bash ./script/test"
      }
    }
  }
}
# test/script

#!/bin/bash

concurrency=$( nproc --all )
echo "-----> Found ${concurrency} CPUs"

spec_node_count=$(( $CI_NODE_TOTAL ))
process_count=$(( $spec_node_count * $concurrency ))

# Heroku buildpack creates a default database and sets $DATABASE_URL pointing to that database
# That means tests running on Heroku CI will ignore database.yml settings
# Also running rake parallel:setup somehow can not create the databases and causes errors
#
# The script below simply clones the default database provided by Heroku
# and then splits the tests into groups so that we can have as many processes as the number of CPUs

regex="^postgres:\/\/([a-zA-Z0-9]+):([a-zA-Z0-9]+)@([a-zA-Z0-9]+):([0-9]+)/([a-zA-Z0-9_]+)"

if [[ $DATABASE_URL =~ $regex ]]
then
  export DB_USERNAME="${BASH_REMATCH[1]}" # random value created by the buildpack
  export DB_PASSWORD="${BASH_REMATCH[2]}" # random value created by the buildpack
  export DB_HOST="${BASH_REMATCH[3]}" # most probably localhost
  export DB_PORT="${BASH_REMATCH[4]}" # most probably 5432

  buildpack_db_name="${BASH_REMATCH[5]}" # most probably postgres_buildpack_db
  export DB_NAME_PREFIX=$buildpack_db_name

  unset DATABASE_URL # we unset this, so that Rails uses database.yml settings

  # Create new databases using the default database as the template. One database per process
  # This is similar to rake parallel:setup
  # It should create databases such as postgres_buildpack_db2, postgres_buildpack_db3, ...
  echo "-----> Creating test databases for paralel testing"

  for (( idx=2; idx<=$concurrency; idx++ ))
  do
    createdb -O $DB_USERNAME -T $buildpack_db_name ${DB_NAME_PREFIX}${idx}
    echo "       Database ${DB_NAME_PREFIX}${idx} created"
  done

  # Find out which groups will be run on this machine
  # e.g. With 2 performance-l dynos,
  # dyno 1 should run groups 0,1,2,3,4,5,6,7
  # dyno 2 should run groups 8,9,10,11,12,13,14,15
  process_index_start=$(( $concurrency * $CI_NODE_INDEX ))
  process_index_end=$(( process_index_start + concurrency ))

  groups=$process_index_start
  for (( idx=$process_index_start + 1; idx<$process_index_end; idx++ ))
  do
    groups+=",${idx}"
  done

  echo "-----> Running groups ${groups} from ${process_count} processes"
  bundle exec parallel_rspec spec/ -n $process_count --only-group $groups
else
    echo "Unexpected DATABASE_URL format"
fi
# database.yml

test:
  <<: *default
  database: <%= ENV['DB_NAME_PREFIX'] || 'parasut_test' %><%= ENV['TEST_ENV_NUMBER'] %>
  pool: 5
  host: <%= ENV['DB_HOST'] || '127.0.0.1' %>
  port: <%= ENV['DB_PORT'] || 5432 %>
  username: <%= ENV['DB_USERNAME'] %>
  password: <%= ENV['DB_PASSWORD'] %>

As a result, our test suite, which took around 15 minutes on 4 performance-m dynos, now finishes in around 3 minutes with 4 performance-l dynos.

useful!

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