output.txt

connect! a #<Thread:0x0000010127b6c0 run>
use_connection (from a on #<Thread:0x0000010127b6c0 run>): a
use_connection (from b on #<Thread:0x0000010127b6c0 run>): a
use_connection (from c on #<Thread:0x0000010127a090 run>): a
use_connection (from d on #<Thread:0x0000010127a090 run>): a
use_connection (from e on #<Thread:0x0000010127a090 run>): a

Rakefile

multitask :all => ['a', 'b', 'c', 'd', 'e']

task :a do
  connect(:a)
  use_worksheet(:a)
end

task :b do
  connect(:b)
  use_worksheet(:b)
end

task :c do
  connect(:c)
  use_worksheet(:c)
end

task :d do
  connect(:d)
  use_worksheet(:d)
end

task :e do
  connect(:e)
  use_worksheet(:e)
end

def reset
  @connection = nil
end

def connect(name)
  @connection ||= connect!(name)
end

def connect!(name)
  puts "connect! #{name} #{Thread.current.inspect}"
  name
end

def use_worksheet(name)
  @worksheet = name
  100.times do |n|
    puts "use_worksheet (from #{n}@#{name} on #{Thread.current.inspect}): #{@worksheet} / #{@worksheet == name}"
  end
end