From: Emil Kampp <emil.kampp@...>
Date: 2009-12-10T20:19:07+09:00
Subject: How do I ensure that File.write finished?

Hi there.

I am trying to make a form to update the values in a yml file (my
applications configuration file). This is working kind of fine.
Sometimes it works, sometimes not.

I have confirmed (through logging) that a content for +string+ is always
there. So there is always something trying to be written into the yml
file, but still sometimes it ends up being empty. And an empty
configuration file is no good!

[code]
# server-controller (user generated controller in rails)
  def update
    # This inserts a new setting into the hash
    unless params[:new_setting][:key].blank? and
params[:new_setting][:value].blank?
      params[:settings].collect{ |env, settings|
settings[params[:new_setting][:key].to_sym] =
params[:new_setting][:value].to_s }
    end

    # This writes the hash to the file (See the second snippet for
details)
    ServerSystem::update_configuration(params[:settings])

    # Redirects to the action that restarts the server to load the new
configurations
    redirect_to admin_server_restart_path
  end
[/code]

[code]
# Custom class
    def update_configuration(settings)
      string = settings.to_yaml
      File.new(APP_CONFIG_FILE, "w").write string
    end
[/code]

The problem is that the setup is dodgy, sometimes it works, sometimes it
looks like the server is restarted before the content of +string+ is
written to the configuration file.
How can I ensure that the content has been written before executing next
line of code (the restart in this case)?
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