Openstack 的 RPC使用。

大家都已经很熟悉了RPC了。 比如说nfs就是采用的RPC通信。

尤其SUN RPC 已经成为了C语言开发的经典一种进程间调用机制。

openstack 的RPC 机制， 是基于AMQP 活着其他高级消息协议而实现得远程调用机制。

而oslo.messaging 在这些消息协议基础上实现了很nice的接口。developer 可以很方便的调用。 

oslo messaging wiki 

参考 openstack的developer手册，实现一个RPC 的server端。

http://docs.openstack.org/developer/oslo.messaging/server.html

call_server.py

from oslo_config import cfg
import oslo_messaging

class ServerControlEndpoint(object):

    target = oslo_messaging.Target(namespace='control',
                                   version='2.0')

    def __init__(self, server):
        print "this is ServerControlEndpoint"
        self.server = server

    def stop(self, ctx):
        if server:
            self.server.stop()

class TestEndpoint(object):

    def test(self, ctx, arg):
        print "this is TestEndpoint test server"
        return arg

transport = oslo_messaging.get_transport(cfg.CONF)

print "cfg.CONF: ", cfg.CONF
print "transport: ", transport
target = oslo_messaging.Target(topic='test', server='server1')
print "target: ", target
endpoints = [
    ServerControlEndpoint(None),
    TestEndpoint(),
]
server = oslo_messaging.get_rpc_server(transport, target, endpoints,
                                       executor='blocking')
print "server: ", server
server.start()
server.wait()

 执行, 等待client 调用。

$ python call_server.py

实现一个 RPC的client端

http://docs.openstack.org/developer/oslo.messaging/rpcclient.html

call_client.py

from oslo_config import cfg
import oslo_messaging as messaging

transport = messaging.get_transport(cfg.CONF)
target = messaging.Target(topic='test') #, version='2.0')
client =  messaging.RPCClient(transport, target)
print client.call({}, 'test', arg="hello")
cctxt = client.prepare() # version='2.0')
print cctxt.call({}, 'test', arg="hello")

 执行，可以得到 server段的返回结果。 

$ python call_server.py

notifier.py

http://docs.openstack.org/developer/oslo.messaging/notifier.html 

notification_listener.py

http://docs.openstack.org/developer/oslo.messaging/notification_listener.html