e1c5fd4ac1
Previously, the timer driver caused the background thread to call send-ground-message to indicate that a timer had expired. However, this can lead to a race! In cases where a timer expires very soon, the channel-put of the set-timer instruction leads shortly thereafter to a send-ground-message which then races the establishment of the metalevel-1 subscription to the timer-expired events that are coming from the background thread. The race cannot occur in the sequential implementation because the network makes sure to enqueue the transition actions resulting from the set-timer message delivery ahead of any enqueueing of the timer-expired ground message, so that by the time the ground message is processed, the relevant subscription always exists. In a looser implementation, however, this level of synchronised activity may not exist, and the ground message may overtake the subscription establishment. Therefore, I've changed the driver to instead use ground /assertions/ to signal expired timers. Upon processing of such an assertion, the driver cleans it up. This is very similar to hardware interrupts, where the driver has to "clear the interrupt" in order to let the system continue properly. |
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| doc | ||
| prospect | ||
| .gitignore | ||
| FAQ.md | ||
| Makefile | ||
| README.md | ||
| info.rkt | ||
README.md
Prospect: A Networked, Concurrent, Functional Programming Language
Prospect is an actor-based 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 actors are grouped within task-specific networks (a.k.a. virtual machines) to scope their interactions. Conversations between actors are multi-party (using a publish/subscribe medium), and actors can easily participate in many such conversations at once.
Prospect makes presence notifications an integral part of pub/sub through its shared dataspaces, akin to tuplespaces. Each shared dataspace doubles as the pub/sub subscription table for its network. Actors react to state change notifications reporting changes in a dataspace, including new subscriptions created by peers and removal of subscriptions when a peer exits or crashes. State change notifications serve to communicate changes in demand for and supply of services, both within a single network and across nested layers of networks-within-networks. Programs can give up responsibility for maintaining shared state and for scoping group communications, letting their containing network take on those burdens.
The code
This repository contains a Racket package,
prospect, which includes
-
the implementation of the
#lang prospectlanguage, in theprospectdirectory. -
a TCP echo server example, which listens for connections on port 5999 by default, in
prospect/examples/echo.rkt. Connect to it using, for example,telnet localhost 5999. -
a handful of other examples, in
prospect/examples/.
Compiling and running the code
You will need Racket version 6.2.x or later.
Once you have Racket installed, run
raco pkg install prospect
to install the package from the Racket package repository, or
raco pkg install
from the root directory of the Git checkout to install the package
from a local snapshot. (Alternatively, make link does the same thing.)
This will make #lang prospect available to programs.
At this point, you may load and run any of the example *.rkt files
in the
prospect/examples/
directory.
Copyright
Copyright © Tony Garnock-Jones 2010, 2011, 2012, 2013, 2014, 2015.