Robotics Service Bus

Added ScopeDispatcher in rsb/eventprocessing.py

refs #2531

• rsb/eventprocessing.py (header): updated copyright
  (ScopeDispatcher): new class; maintains a map of scopes to sinks
• test/eventprocessing_test.py (ScopeDispatcherTest): new test case;
  for ScopeDispatcher class

Spread connection sharing in rsb/transport/rsbspread/__init__.py

fixes #2531

A new class Bus manages one Spread connection and its group
memberships. One or more connectors are attached to the Bus and
notifications are routed between the Spread connection and the
attached connectors:

• Notifications originating from OutConnectors are sent via the Spread
  connection and dispatched to In{Push,Pull}Connectors with matching
  scopes

• Notifications received via the Spread connection are dispatched to
  In{Push,Pull}Connectors with matching scopes

The lifecycle of Bus objects is driven by reference counting. The
TransportFactory class creates Bus objects as needed which start out
with a reference count of 1. Each connector that is removed from its
Bus object decreases the reference count by 1. When the reference
count reaches 0, the Bus object deactivates its Spread connection and
self-destructs.

• rsb/transport/rsbspread/__init__.py (import Queue): new import;
  needed for InPullConnector
  (Notification): new class; superclass for notification
  representations
  (IncomingNotification): new class; represents incoming notifications
  (OutgoingNotification): new class; represents outgoing notifications
  (DeserializingHandler.handleMessage): return an IncomingNotification
  object instead of a tuple
  (Bus): new class; manages a Spread connection and Spread group
  memberships; dispatches events to local connectors as well as the
  Spread connection
  (Connector.__init__): changed parameter connection -> bus; changed
  attribute connection -> _bus
  (Connector.getBus): renamed get{Connection -> Bus}
  (Connector.bus): renamed connection -> busch
  (Connector.activate): do not activate connection
  (Connector.deactivate): do not deactivate connection; call Bus.unref
  method instead
  (Connector.getTransportURL): call Bus.getTransportURL
  (InConnector._init): removed memberships attribute; now handled
  by Bus class
  (InConnector.activate): removed Memberships.join call; replaced by
  Bus.addSink call
  (InConnector.deactivate): similar
  (InConnector.notificationToEvent): operate on Notification objects
  instead of tuples
  (InPushConnector.__init): removed receive{Thread,Task}
  attributes; now handled by Bus
  (InPushConnector.activate): removed method; now handled by Bus
  (InpushConnector.deactivate): likewise
  (InPushConnector.handleNotification): renamed
  handleIncomingNotification -> handleNotification
  (InPullConnector._init): removed deserializingHandler
  attribute; now handled by Bus; added _queue attribute
  (InPullConnector.raiseEvent): pop events from __queue instead of
  receiving from a Spread connection
  (InPullConnector.handleNotification): new method; push events onto
  __queue
  (OutConnector.handle): do not send messages via Spread connection;
  instead, construct OutgoingNotification object and submit to bus for
  sending
  (TransportFactory._init): added attributes __logger, __buses and
  __lock
  (TransportFactory.obtainBus): new method; find an reference an
  existing Bus instance or create and register a new one
  (TransportFactory.createInPushConnector): use obtainBus
  (TransportFactory.createInPullConnector): likewise
  (TransportFactory.createOutConnector): likewise
• test/rsbspread_test.py (getConnector): construct and activate a Bus
  object and pass it to the connector