Framework

Pub/Sub framework for distributed services, nodeset.core is based on Foolscap RPC and twisted. Each "node" is a separate unix process, and all events delivering are performed by dispatcher, the special unix process (also based on foolscap RPC).

Code

Simple subscriber. Publisher code is in example/simple/pub.py

from nodeset.core import message, node, utils

class SimpleMessage(message.NodeMessage):

    def __init__(self):
      message.NodeMessage.__init__(self)
      message.Attribute('field1')


class SimpleNode(node.Node):

    @utils.catch('some_event')
    def callbackForWhatever(self, msg):
      print "EVENT: %s" % msg.toJson()


from nodeset.core import utils
from core import SimpleNode

def do_subscribe(node, event_name):
  print "Subscribing for %s event" % event_name
  node.subscribe(event_name)

def _err(failure):
  print failure

from twisted.internet import reactor

utils.setDefaultOptions()

node = SimpleNode(name='nodeAbc', port=6555)
node.start().addCallback(do_subscribe, 'some_event').addErrback(_err)
node.startService()

reactor.run()

Features

• Distributed - nodes and dispatcher(s) could be anywhere in network.
• Stateless
  • dispatcher is completely stateless (after crash/restart the state of dispatcher will be the same as before).
  • nodes share nothing between each other, and restores all subscriptions after dispatcher reconnect
• HTTP support - nodeset-web helps to implement HTTP API based on nodeset.core pub/sub framework
• Monitoring - built in monitoring support [WiP]

nodeset.core components:

• dispatcher - runs on its own, just listen for incoming foolscap RPC calls, and trace which nodes are available, and its health.
• node - Each Node can act as publisher, as well as subscribers.
• node collection - group nodes under one listen port

Install (easy_install based)

python setup.py install (or develop for development)

Examples

There are few examples of NodeSet framework usage:

• example/simple - pub/sub simple implementation

• examples/node.py - example of NodeCollection, as well as Node usage. Subscription example

• examples/mnode_publish.py - example of publishing

To run any of example, first you must run dispatcher:

• nodeset-dispatcher [options]

Node usage example

• nodeset-node [options]
• nodeset-node publisher [options]
• nodeset-node subscriber [options]

Web node usage example

• nodeset-web web [options]

Options for call is similar to twistd tool in twisted framework, base code was taken from twisted, just use --help to find out available options.