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deb-ryu/doc/source/ryu_app_api.rst
YAMAMOTO Takashi 1afea080d6 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>
2013-09-20 09:42:03 +09:00

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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.
=========== ==================================================================
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