31 August 2009

DB indices

I think it'd be pretty nifty to get a daily summary of which indices lead to the fastest replay of yesterday's logs, based on IO and RAM requirements. Anyone know of any tools for doing this?

27 May 2009

Ruby's memcache-client 1.7.2 does NOT support compression; patch it in with 7 lines of code

The Ruby memcache-client 1.7.2 code seems like the most popular memcached client. Alas, memcache-client 1.7.2 does not recognize :compress => true, all the demos out there notwithstanding.
Let's fix this by monkeypatching Zlib compression into Marshal.

require 'zlib'

module Marshal
@@load_uc = method :load
@@dump_uc = method :dump
def self.load(v) @@load_uc[Zlib::Inflate.inflate(v)] end
def self.dump(v) Zlib::Deflate.deflate(@@dump_uc[v]) end

And there we go!  Four lines of patching Marshal.load for a better memory footprint.

To dissect each phrase of that sentence:
  1. "Four lines": I wanted just to try how well zlib would work on my Marshalled ActiveRecord objects and html fragments, and it did so handily, almost 3:1.  Indeed, the only reason I poked around at the source code is because one of my largest but still highly-compressible HTML fragments was 1.2MB, over the size limit.  I've since gone back to storing large HTML fragments on disk (uncompressed), having found many more values to store in Memcached.
  2. "patching Marshal.load": monkeypatching Marshal is not as bad as String.  Chances are, you use the Marshal format as a blob, and you keep your Marshal files to yourself (and leave external serialization to friendlier fare like JSON).  So, all in all, it's much easier to change the Marshal format than mucking through the memcache-client code.
  3. "better memory footprint": instead of Zlib, try LZMA, with slightly smaller compressed sizes than BZIP and faster decompression times, good properties for cache compression.  But Zlib is already in the standard library, so it's a good first approximation.
The ersatz alias_method_chaining feels kludgy, as does Ruby's distinction between methods and lambdae.  Ah well.


29 March 2009


When art critics get together they talk about Form and Structure and Meaning. When artists get together they talk about where you can buy cheap turpentine. -- Picasso

24 February 2009

A Full Web Service with HTTP caching in 7 lines

Two lovely gems, sinatra and rack-cache. Sinatra is pretty easy web-service-creation, and Rack::Cache is pretty easy http caching. Together? Jubilation.

require 'rubygems'
require 'sinatra'
require 'rack/cache'

use Rack::Cache

get('/quadruple/:n') {
sleep 1
response.headers['Cache-Control'] = 'max-age=1000000'
(params[:n].to_i * 4).to_s

and then
ruby sinatra-add.rb -e production
and you're done.

There are, of course, many other fiddly bits to configure Rack::Cache with, like use Rack::Cache, :entitystore => 'file:/tmp/' if you don't want to keep it all in a hash in memory, and :verbose => false if you don't want that in your logs, but that's basically it.

It's pretty amazing: that's a real live web service, with HTTP caching, in 7 gentle lines. (I don't count the closing brace, nor the sleep 1, which is purely for effect.)

Anyone know an easier way in any other language? Either in number of lines, or in directness of code?

Also, how bad would it be to authbind that to port 80, and just let it go open to the world?

Update: It's interesting to me for the same reason PHP is interesting, both as a social commentary on the bits of plumbing we've agreed upon as useful, and as an aid to wrapping an HTTP interface around some Ada code with its own homegrown database.