os-ken/doc/source/ryu_app_api.rst

Ryu application API

Ryu application programming model

Threads, events, and event queues

Ryu applications are single-threaded entities which implement various functionalities in Ryu. Events are messages between them.

Ryu applications send asynchronous events each other. Besides that, there are some Ryu-internal event sources which are not Ryu applications. One of examples of such event sources is OpenFlow controller. While an event can currently contain arbitrary python objects, it's discouraged to pass complex objects (eg. unpickleable objects) between Ryu applications.

Each Ryu application has a receive queue for events. The queue is FIFO and preserves the order of events. Each Ryu application has a thread for event processing. The thread keep draining the receive queue by dequeueing an event and calling the appropritate event handler for the event type. Because the event handler is called in the context of the event processing thread, it should be careful for blocking. I.e. while an event handler is blocked, no further events for the Ryu application will be processed.

There are kinds of events which are used to implement synchronous inter-application calls between Ryu applications. While such requests uses the same machinary as ordinary events, their replies are put on a queue dedicated to the transaction to avoid deadlock.

While threads and queues is currently implemented with eventlet/greenlet, a direct use of them in a Ryu application is strongly discouraged.

Contexts

Contexts are ordinary python objects shared among Ryu applications. The use of contexts are discouraged for new code.

Create a Ryu application

A Ryu application is a python module which defines a subclass of ryu.base.app_manager.RyuApp. If two or more such classes are defined in a module, the first one (by name order) will be picked by app_manager. Ryu application is singleton: only single instance of a given Ryu application is supported.

Observe events

A Ryu application can register itself to listen for specific events using ryu.controller.handler.set_ev_cls decorator.

Generate events

A Ryu application can raise events by calling appropriate ryu.base.app_manager.RyuApp's methods like send_event or send_event_to_observers.

Event classes

An event class describes a Ryu event generated in the system. By convention, event class names are prefixed by "Event". Events are generated either by the core part of Ryu or Ryu applications. A Ryu application can register its interest for a specific type of event by providing a handler method using ryu.controller.handler.set_ev_cls decorator.

OpenFlow event classes

ryu.controller.ofp_event module exports event classes which describe receptions of OpenFlow messages from connected switches. By convention, they are named as ryu.controller.ofp_event.EventOFPxxxx where xxxx is the name of the corresponding OpenFlow message. For example, EventOFPPacketIn for packet-in message. The OpenFlow controller part of Ryu automatically decodes OpenFlow messages received from switches and send these events to Ryu applications which expressed an interest using ryu.controller.handler.set_ev_cls. OpenFlow event classes are subclass of the following class.

ryu.controller.ofp_event.EventOFPMsgBase

See ofproto_ref for more info about OpenFlow messages.

ryu.base.app_manager.RyuApp

See api_ref.

ryu.controller.handler.set_ev_cls

ryu.controller.handler.set_ev_cls

ryu.controller.controller.Datapath

ryu.controller.controller.Datapath

ryu.controller.event.EventBase

ryu.controller.event.EventBase

ryu.controller.event.EventRequestBase

ryu.controller.event.EventRequestBase

ryu.controller.event.EventReplyBase

ryu.controller.event.EventReplyBase

ryu.controller.ofp_event.EventOFPStateChange

ryu.controller.ofp_event.EventOFPStateChange

ryu.controller.ofp_event.EventOFPPortStateChange

ryu.controller.ofp_event.EventOFPPortStateChange

ryu.controller.dpset.EventDP

ryu.controller.dpset.EventDP

ryu.controller.dpset.EventPortAdd

ryu.controller.dpset.EventPortAdd

ryu.controller.dpset.EventPortDelete

ryu.controller.dpset.EventPortDelete

ryu.controller.dpset.EventPortModify

ryu.controller.dpset.EventPortModify

ryu.controller.network.EventNetworkPort

ryu.controller.network.EventNetworkPort

ryu.controller.network.EventNetworkDel

ryu.controller.network.EventNetworkDel

ryu.controller.network.EventMacAddress

ryu.controller.network.EventMacAddress

ryu.controller.tunnels.EventTunnelKeyAdd

ryu.controller.tunnels.EventTunnelKeyAdd

ryu.controller.tunnels.EventTunnelKeyDel

ryu.controller.tunnels.EventTunnelKeyDel

ryu.controller.tunnels.EventTunnelPort

ryu.controller.tunnels.EventTunnelPort