Why does a Rake task in a loop execute only once?

Question

I have rails application that connects to multiple databases. I wrote custom rake task that looks like this:

task :migrate_accounts_schema => [:environment] do |t|
  users = User.find :all, :conditions => ["state = 2"], :order => "id asc"
  users.each do |user|            
    if user.state == 2
      ActiveRecord::Base.establish_connection(
        :adapter  => "postgresql",
        :host     => user.database_host,
        :port     => user.database_port,
        :username => user.subdomain,
        :password => "#{user.database_password}",
        :database => user.database_name
      )
      Rake::Task["db:migrate"].invoke
    end
  end
end

The problem is that task executes db:migrate only for users[0] user (first user in collection) and there is no errors, just stoppes silently...

Here's output from rake --trace

** Invoke app:migrate_accounts_schema (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute app:migrate_accounts_schema    
** Invoke db:migrate (first_time)
** Invoke environment 
** Execute db:migrate
** Invoke db:schema:dump (first_time)
** Invoke environment 
** Execute db:schema:dump
** Invoke db:migrate 

I have no idea why the rest of users don't get migrated.

Answer 1

I found answer in the Rake source:

http://rake.rubyforge.org/classes/Rake/Task.html#M000115

It says that you have to

Reenable the task, allowing its tasks to be executed if the task is invoked again.

e.g. I used this recently on my project this way:

# db/seed.rb
Rake::Task['catalog:destroy'].invoke

files = Dir.glob("private/catalog/*").sort
files.each do |file|
  next unless File.extname(file) == '.xlsx'
  puts file.split('/').last
  Rake::Task['catalog:upload'].invoke(file)
  Rake::Task['catalog:upload'].reenable
  puts
end

So I run rake catalog:upload[some_file] every loop.

Hope this helps. Also see https://stackoverflow.com/a/1290119/3082929