7fff - think max value » Ruby

Running the gem doc server at startup on OS/X

john — Fri, 18 Jun 2010 14:08:20 +0000

I’ve been traveling a fair bit lately, and have occasionally had spotty Internet access. So my access to documentation for gems and whatnot has been limited.

It would be nice to have all of my gem documentation available locally. But I’m lazy. I don’t want to be typing “gem server” all the time.

So here’s what you do. Locate your appropriate gem command with “which gem”; I’m using rvm to run Ruby 1.9.1, so my answer is: /Users/jgn/.rvm/rubies/ruby-1.9.1-p376/bin/gem

Then create a gemserver.plist file like so, replacing the path to my gem with the path to yours:






	Label
	localhost.gem.server
	ProgramArguments
	
		/Users/jgn/.rvm/rubies/ruby-1.9.1-p376/bin/gem
		server
	
	RunAtLoad

Now copy to /Library/LaunchDaemons

The next type you reboot, you’ll have your gem docs at http://localhost:8808/

favicon at ruby-doc.org the wrong size? And what is it?

john — Wed, 02 Jun 2010 10:57:09 +0000

Here’s the favicon (the image that should show up next to the URL in the browser) for ruby-doc.org:

What IS that? Some kind of stylized “R” + “D”? And why is it the wrong size? Sheesh.

If you must rescue Exception . . .

john — Thu, 29 Oct 2009 15:03:04 +0000

Sometimes you see Ruby code that rescue an exception at the top of the hierarchy:


rescue Exception => e

If you must do that, how about providing a means to control-C, by putting this in the method with the rescue:


trap("INT") do
  puts "Terminating . . . "
 return # or maybe exit
end

Faster Net::HTTP for Ruby 1.8.6

john — Sat, 20 Dec 2008 15:11:27 +0000

We’ve been a bit frustrated at work with Net::HTTP performance (as have so many others) so here’s a monkeypatch for 1.8.6 that combines the buffer size increase in 1.8.7 with Aaron Patterson’s recent tweak to use non-blocking IO (unfortunately, the non-blocking IO patch doesn’t work with HTTPS, which is why we use the buffer size tweak when the @io variable suggests that HTTPS is happening. No guarantee implied, etc.


class Net::BufferedIO #:nodoc:

  alias  ld_rbuf_fill :rbuf_fill

  def rbuf_fill

    BUFSIZE = 1024 * 16

    # HTTPS can't use the non-blocking strategy below in 1.8.6; so at least
    # increase buffer size over 1.8.6 default of 1024
    if !@io.respond_to? :read_nonblock
      timeout(@read_timeout) {
        @rbuf << @io.sysread(BUFSIZE)
      }
      return
    end

    # non-blocking
    begin
      @rbuf << @io.read_nonblock(BUFSIZE)
    rescue Errno::EWOULDBLOCK
      if IO.select([@io], nil, nil, @read_timeout)
        @rbuf << @io.read_nonblock(BUFSIZE)
      else
        raise Timeout::TimeoutError
      end
    end

  end

end

Teaching Ruby and Ruby on Rails again at Harvard

john — Thu, 07 Aug 2008 00:47:11 +0000

Once again, I’m pleased to be offering a course on Ruby and Ruby on Rails at Harvard: course; course site.

We’ll try to avoid this anti-pattern:

Ruby: eval, rescue, and Exception

john — Sat, 07 Jun 2008 00:10:45 +0000

Recently I needed to store bits of Ruby code in the database, and then evaluate them in the context of a particular instance. But one thing I flubbed up was the handling of exceptions. You see, in this situation, if you have bad Ruby code, you will likely raise an exception. My first attempt was, roughly, this code (wrong!):


begin
  eval s
rescue
  # log the fact that s couldn't be eval'ed
end

The catch is that when you use rescue without specify an exception, you are only catching StandardError or one of its subclasses. But eval will raise a SyntaxError (or worse), which is a subclass of ScriptError, which is not a subclass of StandardError. Therefore, you want to rescue an Exception that is further up the hierarchy. In short, better:


begin
  eval s
rescue Exception => e
  # log the fact that s couldn't be eval'ed
end

Nick Sieger provides a post with the Ruby Exception hierarchy, along with some code to generate it dynamically. Too bad this info isn’t in the on-line Pickaxe (http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_exceptions.html).