migrate_concurrently.rb

class MigrateConcurrently
  def initialize; end

  def perform
    # migration taken directly
    # from ActiveRecord
    ActiveRecord::Base.connection.migration_context.migrate
  rescue ActiveRecord::ConcurrentMigrationError
    # we log the details of the migrations
    # through our logger
    Logger.info(
      message: "Migration is already running, waiting to try again",
      type: "infrastructure_run_migrate",
      delay_between_cycles_in_seconds: 3,
      cycle: current_cycle,
      max_cycles: max_cycle,
    )

    sleep 3

    # when we reach the cycles limit
    # we should stop the process
    # and raise an error
    if max_cycle?
      raise Exception, """
      Max cycles reached after trying #{@cycles.current} times.
      Something might be wrong with the migration process.
      """
    end

    # let's increment
    # and try again
    next_cycle
    perform
  end

  def current_cycle
    @current_cycle ||= 1
  end

  def max_cycle
    @max_cycle ||= 2
  end

  def next_cycle
    @current_cycle += 1
  end

  def max_cycle?
    @current_cycle >= @max_cycle
  end
end