| Andrew Cooke | Contents | Latest | RSS | Twitter | Previous | Next


Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

C-ORM: docs, API.

Last 100 entries

Why Information Grows; The Blindness Of The Chilean Elite; Some Victoriagate Links; This Is Why I Left StackOverflow; New TLS Implementation; Maths for Physicists; How I Am 8; 1000 Word Philosophy; Cyberpunk Reading List; Detailed Discussion of Message Dispatch in ParserCombinator Library for Julia; FizzBuzz in Julia w Dependent Types; kokko - Design Shop in Osaka; Summary of Greece, Currently; LLVM and GPUs; See Also; Schoolgirl Groyps (Maths); Japanese Lit; Another Example - Modular Arithmetic; Music from United; Python 2 and 3 compatible alternative.; Read Agatha Christie for the Plot; A Constructive Look at TempleOS; Music Thread w Many Recommendations; Fixed Version; A Useful Julia Macro To Define Equality And Hash; k3b cdrom access, OpenSuse 13.1; Week 2; From outside, the UK looks less than stellar; Huge Fonts in VirtualBox; Keen - Complex Emergencies; The Fallen of World War II; Some Spanish Fiction; Calling C From Fortran 95; Bjork DJ Set; Z3 Example With Python; Week 1; Useful Guide To Starting With IJulia; UK Election + Media; Review: Reinventing Organizations; Inline Assembly With Julia / LLVM; Against the definition of types; Dumb Crypto Paper; The Search For Quasi-Periodicity...; Is There An Alternative To Processing?; CARDIAC (CARDboard Illustrative Aid to Computation); The Bolivian Case Against Chile At The Hague; Clear, Cogent Economic Arguments For Immigration; A Program To Say If I Am Working; Decent Cards For Ill People; New Photo; Luksic And Barrick Gold; President Bachelet's Speech; President Bachelet's Speech; Baltimore Primer; Baltimore Primer; libxml2 Parsing Stream; libxml2 Parsing Stream; configure.ac Recipe For Library Path; configure.ac Recipe For Library Path; The Davalos Affair For Idiots; Not The Onion: Google Fireside Chat w Kissinger; Not The Onion: Google Fireside Chat w Kissinger; Bicycle Wheels, Inertia, and Energy; Bicycle Wheels, Inertia, and Energy; Another Tax Fraud; Google's Borg; Google's Borg; A Verion That Redirects To Local HTTP Server; Spanish Accents For Idiots; Spanish Accents For Idiots; Aluminium Cans; Aluminium Cans; Advice on Spray Painting; Advice on Spray Painting; Female View of Online Chat From a Male; Female View of Online Chat From a Male; UX Reading List; UX Reading List; S4 Subgroups - Geometric Interpretation; S4 Subgroups - Geometric Interpretation; Fucking Email; Fucking Email; The SQM Affair For Idiots; The SQM Affair For Idiots; Using Kolmogorov Complexity; Using Kolmogorov Complexity; Oblique Strategies in bash; Oblique Strategies in bash; Curses Tools; Curses Tools; Markov Chain Monte Carlo Without all the Bullshit; Markov Chain Monte Carlo Without all the Bullshit; Email Para Matias Godoy Mercado; The Penta Affair For Idiots; The Penta Affair For Idiots; Example Code To Create numpy Array in C; Example Code To Create numpy Array in C; Good Article on Bias in Graphic Design (NYTimes); Good Article on Bias in Graphic Design (NYTimes); Do You Backup githb?; Do You Backup github?

© 2006-2015 Andrew Cooke (site) / post authors (content).

HowTo Make POJO Workflows

From: "andrew cooke" <andrew@...>

Date: Tue, 16 Jan 2007 11:44:16 -0300 (CLST)

I think I just solved the POJO workflow problem.  I'm not sure this works
(in particular, I'm not sure how it would interact with transactions), but
if it does it would be amazingly sweet.

OK, so the problem is that if you're doing lightweight SOA, you write
services as POJOs.  That's fine for "one shot" services that have no
persistent state between messages, but doesn't work so well for services
that need to maintain conversational state - typically these are composite
services (orchestrators) which call one service ("synchronously") and then

The root of the problem is the "synchronous" call.  This can be
constructed from asynchronous messaging using "replyTo" in an envelope -
no problem there - but the replyTo identifies an *instance*.  So if the
instance dies while the call is being made, the return value has nowhere
to go.

And the obvious solution is to explicitly store state before calls and use
some kind of index to retrieve state for the response.  But this requires
(as far as I can tell, until now) explicit management of state inside the
POJO, or the use of a separate workflow (eg. BPEL engine).

The alternative is to somehow convert a POJO so that it stores state
transparently.  How to do this has not been clear 'til now, although it's
pretty obvious that continuations would be a component.

So.  Here's the trick.  You wrap the *called* service (typically injected
via Spring) in a dynamic proxy which preserves the interface but, when
- triggers a new thread to continue with processing in the injected class
(which is presumably an adapter to call messaging).
- constructs a continuation in the old thread and then throws a runtime
exception (is this exception necessary?  perhaps the wrapper simply stores
the continuation?)

The composite service is itself wrapped in a dynamic proxy which catches
the exception raised at the bean's entry point.

When the response comes back to the wrapper around the called service it
collaborates with the wrapper around the caller bean (or if the exception
is not necessary, simply retrieves the continuation itself) to restart the

Obviously a lot of details need still to be worked out :o)

But the hard part has always been, until now, how to get the continuation
in the right place.  This was hard because I was looking at the composite
service.  What is new here is the idea that you have a wrapper around the
target service (or rather, its messaging adapter).

For background on the problem see http://www.acooke.org/cute/NotesonSta0.html


Porqi - the POJO POrquestrator

From: "andrew cooke" <andrew@...>

Date: Sun, 21 Jan 2007 19:45:59 -0300 (CLST)

I've started work on a small library to implement this.  It assumes Spring
and uses factories and dynamic proxies to wrap POJOs.

So far I have the basic framework - the wrapper factories - almost
complete.  Next I need to add a strategy for a particular continuation
library that will be responsible for managing threads, state etc.  The
first implementation will do nothing, of course, but will allow testing. 
The persistence will be a separate pluggable strategy.

The code is pretty cute - it's amazing the level of metaprogramming
possible in pure Java (well, not so pure with the continuation libraries).


Asynchronous Java

From: "andrew cooke" <andrew@...>

Date: Tue, 30 Jan 2007 08:27:19 -0300 (CLST)

This works - at least, I've just got some test cases running with a
library that converts Java from sychronous to asynchronous calls.  I don't
yet have the stored state, but that should be a small amount of additional
work (the architecture is modular - I just need continuations based thread

Here's the test code.  Depending on whether "Pojo" is injected into
"Composite" via a service method or not (ie one specified in the
interface) it is called either synchronously or asynchronously.

  public void testSynchronousCall() throws Throwable {
    assertEquals(1, service.callCount(Target.COMPONENT));
    assertEquals(3, service.callCount(Target.COMPONENT));

  public void testAsynchronousCall() throws Throwable {
    assertEquals(1, service.callCount(Target.SERVICE));
    assertEquals(3, service.callCount(Target.SERVICE));

public interface CompositeIface {
  boolean sameThreadName(Target target);
  int callCount(Target target);
  public void setService(PojoIface service);

public interface PojoIface {
  String threadName();
  int callCount();


Comment on this post