Marketplace: Bringing the Network into the Programming Language

Marketplace is a concurrent language able to express communication, enforce isolation, and manage resources. Network-inspired extensions to a functional core represent imperative actions as values, giving side-effects locality and enabling composition of communicating processes.

Collaborating programs are grouped within task-specific virtual machines (VMs) to scope their interactions. Conversations between programs are multi-party (using a publish/subscribe medium), and programs can easily participate in many such conversations at once.

Marketplace makes presence notifications an integral part of pub/sub. Programs react to presence and absence notifications that report the comings and goings of their peers. Presence serves to communicate changes in demand for and supply of services, both within a VM and across nested VM layers. Programs can give up responsibility for maintaining presence information and for scoping group communications to their containing VM.

Documentation

A (draft) manual for Marketplace is available here.

The code

This repository contains a Racket package, marketplace, which includes

• the implementation of the #lang marketplace language, in the top directory.

• a TCP echo server example, in examples/echo-paper.rkt.

• a TCP chat server example, in examples/chat-paper.rkt.

• Haskell, Erlang and Python implementations of the chat server for comparison, in examples/chat.hs, chat.erl, and chat.py respectively.

Compiling and running the code

You will need Racket version 5.3.4.11 or later.

Once you have Racket installed, run

raco pkg install --link `pwd`

from the root directory of the Git checkout to install the package in your Racket system. (Alternatively, make link does the same thing.) This will make #lang marketplace available to programs.

It will take several minutes to compile the code. On my Macbook Air, it takes around 10 minutes; on my ridiculously fast desktop machine, it still takes around 2 minutes.

At this point, you may load and run any of the example *.rkt files in the examples/ directory.

Note that both the echo server and chat server examples do not print any output on standard output: instead, they simply start running and silently await TCP connections. Once one of the servers is running, in a separate window, try telnet localhost 5999.

Note also that both the echo server and the chat server use port 5999, so you cannot run both simultaneously.

Copyright

Copyright © Tony Garnock-Jones 2010, 2011, 2012, 2013.