deb-ryu/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 another queue dedicated to replies to avoid deadlock. (Because, unlike erlang, our queue doesn't support selective receive.) It's assumed that the number of in-flight synchronous requests from a Ryu application is at most 1.

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 have at least the following attributes.

Attribute	Description
msg	An object which describes the corresponding OpenFlow message.
msg.datapath	A ryu.controller.controller.Datapath instance which describes an OpenFlow switch from which we received this OpenFlow message.

The msg object has some more additional members whose values are extracted from the original OpenFlow message. See ofproto_ref for more info about OpenFlow messages.

ryu.base.app_manager.RyuApp

The base class for Ryu applications.

class attributes

A RyuApp subclass can have class attributes with the following special names, which are recognized by app_manager.

_CONTEXTS

A dictionary to specify contexts which this Ryu application wants to use. Its key is a name of context and its value is an ordinary class which implements the context. The class is instantiated by app_manager and the instance is shared among RyuApp subclasses which has _CONTEXTS member with the same key. A RyuApp subclass can obtain a reference to the instance via its __init__'s kwargs as the following.

_CONTEXTS = {
    'network': network.Network
}

def __init__(self, *args, *kwargs):
    self.network = kwargs['network']

_EVENTS

A list of event classes which this RyuApp subclass would generate. This should be specified if and only if event classes are defined in a different python module from the RyuApp subclass is.

OFP_VERSIONS

A list of supported OpenFlow versions for this RyuApp. For example:

OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION,
                ofproto_v1_2.OFP_VERSION]

If multiple Ryu applications are loaded in the system, the intersection of their OFP_VERSIONS is used.

instance attributes

A RyuApp instance provides the following attributes.

__init__(self, *args, *kwargs)

RyuApp subclasses are instantiated after ryu-manager loaded all requested Ryu application modules. __init__ should call RyuApp.__init with the same arguments. It's illegal to send any events in __init__.

name

The name of the class used for message routing among Ryu applications. (Cf. send_event) It's set to __class.__name by RyuApp.__init__. It's discouraged to override this value.

send_request(self, req)

Make a synchronous request. Set req.sync to True, send it to a Ryu application specified by req.dst, and block until receiving a reply. Returns the received reply. The argument should be an instance of EventRequestBase.

send_reply(self, rep)

Send a reply for a synchronous request sent by send_request. The argument should be an instance of EventReplyBase.

send_event(self, name, ev)

Send the specified event to the RyuApp instance specified by name.

send_event_to_observers(self, ev)

Send the specified event to all observers of this RyuApp.

ryu.controller.handler.set_ev_cls(ev_cls, dispatchers=None)

A decorator for Ryu application to declare an event handler. Decorated method will become an event handler. ev_cls is an event class whose instances this RyuApp wants to receive. dispatchers argument specifies one of the following negotiation phases (or a list of them) for which events should be generated for this handler. Note that, in case an event changes the phase, the phase before the change is used to check the interest.

Negotiation phase	Description
ryu.controller.handler.HANDSHAKE_DISPATCHER	Sending and waiting for hello message
ryu.controller.handler.CONFIG_DISPATCHER	Version negotiated and sent features-request message
ryu.controller.handler.MAIN_DISPATCHER	Switch-features message received and sent set-config message
ryu.controller.handler.DEAD_DISPATCHER	Disconnect from the peer. Or disconnecting due to some unrecoverable errors.

ryu.controller.controller.Datapath

A class to describe an OpenFlow switch connected to this controller. An instance has the following attributes.

Attribute	Description
id	64-bit OpenFlow Datapath ID. Only available for ryu.controller.handler.MAIN_DISPATCHER phase.
ofproto	A module which exports OpenFlow definitions, mainly constants appeared in the specification, for the negotiated OpenFlow version. For example, ryu.ofproto.ofproto_v1_0 for OpenFlow 1.0.
ofproto_parser	A module which exports OpenFlow wire message encoder and decoder for the negotiated OpenFlow version. For example, ryu.ofproto.ofproto_v1_0_parser for OpenFlow 1.0.
ofproto_parser.OFPxxxx(datapath, ....)	A callable to prepare an OpenFlow message for the given switch. It can be sent with Datapath.send_msg later. xxxx is a name of the message. For example OFPFlowMod for flow-mod message. Arguemnts depend on the message.
set_xid(self, msg)	Generate an OpenFlow XID and put it in msg.xid.
send_msg(self, msg)	Queue an OpenFlow message to send to the corresponding switch. If msg.xid is None, set_xid is automatically called on the message before queueing.
send_packet_out	deprecated
send_flow_mod	deprecated
send_flow_del	deprecated
send_delete_all_flows	deprecated
send_barrier	Queue an OpenFlow barrier message to send to the switch.
send_nxt_set_flow_format	deprecated
is_reserved_port	deprecated

ryu.controller.event.EventBase

The base of all event classes. A Ryu application can define its own event type by creating a subclass.

ryu.controller.event.EventRequestBase

The base class for synchronous request for RyuApp.send_request.

ryu.controller.event.EventReplyBase

The base class for synchronous request reply for RyuApp.send_reply.

ryu.controller.ofp_event.EventOFPStateChange

An event class for negotiation phase change notification. An instance of this class is sent to observer after changing the negotiation phase. An instance has at least the following attributes.

Attribute	Description
datapath	ryu.controller.controller.Datapath instance of the switch

ryu.controller.dpset.EventDP

An event class to notify connect/disconnect of a switch. For OpenFlow switches, one can get the same notification by observing ryu.controller.ofp_event.EventOFPStateChange. An instance has at least the following attributes.

Attribute	Description
dp	A ryu.controller.controller.Datapath instance of the switch
enter	True when the switch connected to our controller. False for disconnect.

ryu.controller.dpset.EventPortAdd

An event class for switch port status notification. This event is generated when a new port is added to a switch. For OpenFlow switches, one can get the same notification by observing ryu.controller.ofp_event.EventOFPPortStatus. An instance has at least the following attributes.

Attribute	Description
dp	A ryu.controller.controller.Datapath instance of the switch
port	port number

ryu.controller.dpset.EventPortDelete

An event class for switch port status notification. This event is generated when a port is removed from a switch. For OpenFlow switches, one can get the same notification by observing ryu.controller.ofp_event.EventOFPPortStatus. An instance has at least the following attributes.

Attribute	Description
dp	A ryu.controller.controller.Datapath instance of the switch
port	port number

ryu.controller.dpset.EventPortModify

An event class for switch port status notification. This event is generated when some attribute of a port is changed. For OpenFlow switches, one can get the same notification by observing ryu.controller.ofp_event.EventOFPPortStatus. An instance has at least the following attributes.

Attribute	Description
dp	A ryu.controller.controller.Datapath instance of the switch
port	port number

ryu.controller.network.EventNetworkPort

An event class for notification of port arrival and deperture. This event is generated when a port is introduced to or removed from a network by the REST API. An instance has at least the following attributes.

Attribute	Description
network_id	Network ID
dpid	OpenFlow Datapath ID of the switch to which the port belongs.
port_no	OpenFlow port number of the port
add_del	True for adding a port. False for removing a port.

ryu.controller.network.EventNetworkDel

An event class for network deletion. This event is generated when a network is deleted by the REST API. An instance has at least the following attributes.

Attribute	Description
network_id	Network ID

ryu.controller.network.EventMacAddress

An event class for end-point MAC address registration. This event is generated when a end-point MAC address is updated by the REST API. An instance has at least the following attributes.

Attribute	Description
network_id	Network ID
dpid	OpenFlow Datapath ID of the switch to which the port belongs.
port_no	OpenFlow port number of the port
mac_address	The old MAC address of the port if add_del is False. Otherwise the new MAC address.
add_del	False if this event is a result of a port removal. Otherwise True.

ryu.controller.tunnels.EventTunnelKeyAdd

An event class for tunnel key registration. This event is generated when a tunnel key is registered or updated by the REST API. An instance has at least the following attributes.

Attribute	Description
network_id	Network ID
tunnel_key	Tunnel Key

ryu.controller.tunnels.EventTunnelKeyDel

An event class for tunnel key registration. This event is generated when a tunnel key is removed by the REST API. An instance has at least the following attributes.

Attribute	Description
network_id	Network ID
tunnel_key	Tunnel Key

ryu.controller.tunnels.EventTunnelPort

An event class for tunnel port registration. This event is generated when a tunnel port is added or removed by the REST API. An instance has at least the following attributes.

Attribute	Description
dpid	OpenFlow Datapath ID
port_no	OpenFlow port number
remote_dpid	OpenFlow port number of the tunnel peer
add_del	True for adding a tunnel. False for removal.