From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-11-03T00:08:08+09:00
Subject: Re: fastcgi performance problems and ruby

On Tuesday 02 November 2004 09:49 am, Brian Candler wrote:
| On Tue, Nov 02, 2004 at 11:29:09PM +0900, trans.  (T. Onoma) wrote:
| > I'm also curious about Singleton Class, i.e. I recall (it was a while
| > ago) somthing about modifying CGI to be a Singleton class rather then a
| > regular class --that seemed helpful.
|
| That sentence doesn't make much sense to me - can you define what you mean
| by "modifying .. to be a Singleton class rather than a regular class" ??

Ah yes, the old name confusion. Sorry. I'm _not_ referring to Virtual class 
(or Instance class), which is also called singleton. That's different. (BTW 
we really need to get onto this new naming convention to prevent this 
confusion! Yes?) I'm referring to the other kind where by only one instance 
of a class can exist. See Singleton module for more info on that.

So if I make CGI singleton, then only one instance of it ever exists 
--presumably even between http requests. Thus an increase in performance. But 
like I said I'm not perfectly clear about how it all works, and how FCGI 
might fit in.

HTH,
T.


| Remember that:
|
| 1. CGI is_a Class (i.e. CGI is an object, an instance of class Class)
|
| 2. This object has a singleton class; that is, methods which apply to
|    CGI itself, and not to any instance of class CGI, nor any other
|    instance of class Class.
|
|    For example, CGI.escapeHTML is a method within CGI's singleton class
|
| 3. Singleton classes are anonymous; there is no need to name them, as they
|    are always only associated with one object.
|
| So I can't really make sense of what you're suggesting. If you've not seen
| it, have a look at http://www.rubygarden.org/ruby?SingletonTutorial and see
| if that makes the terminology any clearer.
|
| The issue with performance is: CGI.new creates a new object (an instance of
| class CGI), and at object creation time, a whole bunch of methods are added
| at run-time to that instance's singleton class.
|
| e.g.
|
|   a = CGI.new("html3")
|   b = CGI.new("html4")
|
| creates two objects, each of which is an instance of CGI, but if you look
| in the source for cgi.rb you can see a lot of work is done in the
| initialize() method:
|
|     case type
|     when "html3"
|       extend Html3
|       element_init()
|       extend HtmlExtension
|     when "html4"
|       extend Html4
|       element_init()
|       extend HtmlExtension
|
| In turn, method element_init does a whole load of work defining methods the
| slow way, with code such as
|
|       for element in %w[ A TT I B U STRIKE BIG SMALL SUB SUP EM STRONG
|           DFN CODE SAMP KBD VAR CITE FONT ADDRESS DIV center MAP
|           APPLET PRE XMP LISTING DL OL UL DIR MENU SELECT table TITLE
|           STYLE SCRIPT H1 H2 H3 H4 H5 H6 TEXTAREA FORM BLOCKQUOTE
|           CAPTION ]
|         methods += <<-BEGIN + nn_element_def(element) + <<-END
|           def #{element.downcase}(attributes = {})
|         BEGIN
|           end
|         END
|       end
|       ...
|       eval(methods)
|
| I'm sure this was to save the programmer having to enumerate all these
| methods in the mixin, but I'd have thought it could be done more
| efficiently than that (by defining the methods once in the mixin, not at
| run-time in every object instance)
|
| Perhaps the assumption in the CGI library is that normally a CGI is a
| one-shot process: there is no point carefully preparing mixins for
| Html3/Html4/Html4Tr/Html4Fr if at runtime only one will be used and then
| the CGI will terminate. But that assumption is not true for a FastCGI
| environment.
|
| But actually, if you just use CGI.new without passing a html type, this
| heavyweight construction work isn't done anyway.
|
| Regards,
|
| Brian.