6.0 KiB
OS-Ken application API
OS-Ken application programming model
Threads, events, and event queues
OS-Ken applications are single-threaded entities which implement various functionalities in OS-Ken. Events are messages between them.
OS-Ken applications send asynchronous events to each other. Besides that, there are some OS-Ken-internal event sources which are not OS-Ken applications. One of the examples of such event sources is the OpenFlow controller. While an event can currently contain arbitrary python objects, it's discouraged to pass complex objects (eg. unpickleable objects) between OS-Ken applications.
Each OS-Ken application has a receive queue for events. The queue is FIFO and preserves the order of events. Each OS-Ken application has a thread for event processing. The thread keeps 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 when blocking. While an event handler is blocked, no further events for the OS-Ken application will be processed.
There are kinds of events which are used to implement synchronous inter-application calls between OS-Ken applications. While such requests use the same machinery as ordinary events, their replies are put on a queue dedicated to the transaction to avoid deadlock.
While threads and queues are currently implemented with eventlet/greenlet, a direct use of them in a OS-Ken application is strongly discouraged.
Contexts
Contexts are ordinary python objects shared among OS-Ken applications. The use of contexts is discouraged for new code.
Create a OS-Ken application
A OS-Ken application is a python module which defines a subclass of os_ken.base.app_manager.OSKenApp. If two or more such classes are defined in a module, the first one (by name order) will be picked by app_manager. An OS-Ken application is singleton: only a single instance of a given OS-Ken application is supported.
Observe events
A OS-Ken application can register itself to listen for specific events using os_ken.controller.handler.set_ev_cls decorator.
Generate events
A OS-Ken application can raise events by calling appropriate os_ken.base.app_manager.OSKenApp's methods like send_event or send_event_to_observers.
Event classes
An event class describes a OS-Ken event generated in the system. By convention, event class names are prefixed by "Event". Events are generated either by the core part of OS-Ken or OS-Ken applications. A OS-Ken application can register its interest for a specific type of event by providing a handler method using the os_ken.controller.handler.set_ev_cls decorator.
OpenFlow event classes
os_ken.controller.ofp_event module exports event classes which describe receptions of OpenFlow messages from connected switches. By convention, they are named as os_ken.controller.ofp_event.EventOFPxxxx where xxxx is the name of the corresponding OpenFlow message. For example, EventOFPPacketIn for the packet-in message. The OpenFlow controller part of OS-Ken automatically decodes OpenFlow messages received from switches and send these events to OS-Ken applications which expressed an interest using os_ken.controller.handler.set_ev_cls. OpenFlow event classes are subclasses of the following class.
os_ken.controller.ofp_event.EventOFPMsgBase
See ofproto_ref for
more info about OpenFlow messages.
os_ken.base.app_manager.OSKenApp
See api_ref.
os_ken.controller.handler.set_ev_cls
os_ken.controller.handler.set_ev_cls
os_ken.controller.controller.Datapath
os_ken.controller.controller.Datapath
os_ken.controller.event.EventBase
os_ken.controller.event.EventBase
os_ken.controller.event.EventRequestBase
os_ken.controller.event.EventRequestBase
os_ken.controller.event.EventReplyBase
os_ken.controller.event.EventReplyBase
os_ken.controller.ofp_event.EventOFPStateChange
os_ken.controller.ofp_event.EventOFPStateChange
os_ken.controller.ofp_event.EventOFPPortStateChange
os_ken.controller.ofp_event.EventOFPPortStateChange
os_ken.controller.dpset.EventDP
os_ken.controller.dpset.EventDP
os_ken.controller.dpset.EventPortAdd
os_ken.controller.dpset.EventPortAdd
os_ken.controller.dpset.EventPortDelete
os_ken.controller.dpset.EventPortDelete
os_ken.controller.dpset.EventPortModify
os_ken.controller.dpset.EventPortModify
os_ken.controller.network.EventNetworkPort
os_ken.controller.network.EventNetworkPort
os_ken.controller.network.EventNetworkDel
os_ken.controller.network.EventNetworkDel
os_ken.controller.network.EventMacAddress
os_ken.controller.network.EventMacAddress
os_ken.controller.tunnels.EventTunnelKeyAdd
os_ken.controller.tunnels.EventTunnelKeyAdd
os_ken.controller.tunnels.EventTunnelKeyDel
os_ken.controller.tunnels.EventTunnelKeyDel
os_ken.controller.tunnels.EventTunnelPort
os_ken.controller.tunnels.EventTunnelPort