我一直在开始使用AMQP gem doc中提供的RabbitMQ RPC sample code,尝试编写执行同步远程调用的非常简单的代码:
require "amqp"
module RPC
class Base
include EM::Deferrable
def rabbit(rabbit_callback)
rabbit_loop = Proc.new {
AMQP.connect do |connection|
AMQP::Channel.new(connection) do |channel|
channel.queue("rpc.queue", :exclusive => false, :durable => true) do |requests_queue|
self.callback(&rabbit_callback)
self.succeed(connection, channel, requests_queue)
end # requests_queue
end # AMQP.channel
end # AMQP.connect
Signal.trap("INT") { connection.close { EM.stop } }
Signal.trap("TERM") { connection.close { EM.stop } }
}
if !EM.reactor_running?
EM.run do
rabbit_loop.call
end
else
rabbit_loop.call
end
end
end
class Server < Base
def run
server_loop = Proc.new do |connection, channel, requests_queue|
consumer = AMQP::Consumer.new(channel, requests_queue).consume
consumer.on_delivery do |metadata, payload|
puts "[requests] Got a request #{metadata.message_id}. Sending a reply to #{metadata.reply_to}..."
channel.default_exchange.publish(Time.now.to_s,
:routing_key => metadata.reply_to,
:correlation_id => metadata.message_id,
:mandatory => true)
metadata.ack
end
end
rabbit(server_loop)
end
end
class Client < Base
def sync_push(request)
result = nil
sync_request = Proc.new do |connection, channel, requests_queue|
message_id = Kernel.rand(10101010).to_s
response_queue = channel.queue("", :exclusive => true, :auto_delete => true)
response_queue.subscribe do |headers, payload|
if headers.correlation_id == message_id
result = payload
connection.close { EM.stop }
end
end
EM.add_timer(0.1) do
puts "[request] Sending a request...#{request} with id #{message_id}"
channel.default_exchange.publish(request,
:routing_key => requests_queue.name,
:reply_to => response_queue.name,
:message_id => message_id)
end
end
rabbit(sync_request)
result
end
end
end
这个想法非常简单:我希望消息队列始终准备就绪(这由rabbit
方法处理)。每当客户端想要发送请求时,它首先创建响应的临时队列以及消息ID;然后,它将请求发布到主消息队列,并等待临时队列中具有相同消息ID的响应,以便知道该特定请求的答案何时准备就绪。我想message_id
在某种程度上与临时队列是多余的(因为队列也应该是唯一的)。
我现在使用此客户端/服务器代码运行虚拟脚本
# server session
>> server = RPC::Server.new
=> #<RPC::Server:0x007faaa23bb5b0>
>> server.run
Updating client properties
[requests] Got a request 3315740. Sending a reply to amq.gen-QCv8nP2dI5Qd6bg2Q1Xhk0...
和
# client session
>> client = RPC::Client.new
=> #<RPC::Client:0x007ffb6be6aed8>
>> client.sync_push "test 1"
Updating client properties
[request] Sending a request...test 1 with id 3315740
=> "2012-11-02 21:58:45 +0100"
>> client.sync_push "test 2"
AMQ::Client::ConnectionClosedError: Trying to send frame through a closed connection. Frame is #<AMQ::Protocol::MethodFrame:0x007ffb6b9c83d0 @payload="\x002\x00\n\x00\x00\x00\f\x00\x00\x00\x00", @channel=1>
有两点我真的不明白:
Client
代码中,如果我希望实际发布消息,为什么必须调用EM.add_timer
?为什么使用EM.next_tick
不起作用?我的理解是,在这里调用发布时,“一切”应该是“准备好的”。遗憾的是,很少有在线处理EM / AMQP的代码,所以任何帮助都将深表感谢! 关于效率的任何评论也将受到高度赞赏。
答案 0 :(得分:3)
挖掘文档,我终于发现我实际上需要once_declared
回调以确保在客户端开始使用它时队列已准备就绪。
关于连接问题,似乎不知何故,使用EM::Deferrable
会导致问题,因此(非常不令人满意)解决方案只包括不包括EM::Deferrable
。
require "amqp"
module RPC
module Base
def rabbit(rabbit_callback)
rabbit_loop = Proc.new {
AMQP.start do |connection|
AMQP::Channel.new(connection) do |channel|
channel.queue("rpc.queue", :exclusive => false, :durable => true) do |requests_queue|
requests_queue.once_declared do
rabbit_callback.call(connection, channel, requests_queue)
end
end
end
end
Signal.trap("INT") { AMQP.stop { EM.stop } }
Signal.trap("TERM") { AMQP.stop { EM.stop } }
}
if !EM.reactor_running?
@do_not_stop_reactor = false
EM.run do
rabbit_loop.call
end
else
@do_not_stop_reactor = true
rabbit_loop.call
end
end
end
class Server
include Base
def run
server_loop = Proc.new do |connection, channel, requests_queue|
consumer = AMQP::Consumer.new(channel, requests_queue).consume
consumer.on_delivery do |metadata, payload|
puts "[requests] Got a request #{metadata.message_id}. Sending a reply to #{metadata.reply_to}..."
channel.default_exchange.publish(Time.now.to_s,
:routing_key => metadata.reply_to,
:correlation_id => metadata.message_id,
:mandatory => true)
metadata.ack
end
end
rabbit(server_loop)
end
end
class Client
include Base
def sync_push(request)
result = nil
sync_request = Proc.new do |connection, channel, requests_queue|
message_id = Kernel.rand(10101010).to_s
response_queue = channel.queue("", :exclusive => true, :auto_delete => true)
response_queue.subscribe do |headers, payload|
if headers.correlation_id == message_id
result = payload
AMQP.stop { EM.stop unless @do_not_stop_reactor }
end
end
response_queue.once_declared do
puts "[request] Sending a request...#{request} with id #{message_id}"
channel.default_exchange.publish(request,
:routing_key => requests_queue.name,
:reply_to => response_queue.name,
:message_id => message_id)
end
end
rabbit(sync_request)
result
end
end
end