doc: ryu app api overview

mostly taken from ryu.wiki/API.md and conveted by hand.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

1 files changed, 458 insertions, 0 deletions

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+*******************
+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 :ref:`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.
+
+.. code-block:: python
+
+    _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:
+
+.. code-block:: python
+
+    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.
+=========== ==================================================================