如果客户端配置为接收消息创建临时队列，是否可以配置只允许创建一个队列？ 如果有错误的客户端在服务器上创建了太多队列，它对服务器来说会是一个大问题吗？
如何配置以防止客户浪费资源？
-module(amqp_example).
-include("amqp_client.hrl").
-compile([export_all]).
test() ->
%% Start a network connection
{ok, Connection} = amqp_connection:start(#amqp_params_network{}),
%% Open a channel on the connection
{ok, Channel} = amqp_connection:open_channel(Connection),
%% Declare a queue
#'queue.declare_ok'{queue = Q}
= amqp_channel:call(Channel, #'queue.declare'{}),
ok = create_temp_queue(Channel,10),
%% Publish a message
Payload = <<"foobar">>,
Publish = #'basic.publish'{exchange = <<>>, routing_key = Q},
amqp_channel:cast(Channel, Publish, #amqp_msg{payload = Payload}),
%% Get the message back from the queue
Get = #'basic.get'{queue = Q},
{#'basic.get_ok'{delivery_tag = Tag}, _Content}
= amqp_channel:call(Channel, Get),
%% Do something with the message payload
%% (some work here)
%% Ack the message
amqp_channel:cast(Channel, #'basic.ack'{delivery_tag = Tag}),
%% Close the channel
amqp_channel:close(Channel),
%% Close the connection
amqp_connection:close(Connection),
ok.
create_temp_queue(Channel,Loop)->
[ %% Declare a queue
#'queue.declare_ok'{queue = _Q}
= amqp_channel:call(Channel, #'queue.declare'{})
||
_X <- lists:seq(1,Loop)].
(emacs@yus-iMac.local)58> amqp_example:test().
** exception error: no match of right hand side value
[{'queue.declare_ok',
<<"amq.gen-AqAaMLydgMf43y_XoYSdq5">>,0,0},
{'queue.declare_ok',
<<"amq.gen-A75g--nsvheNbwYMr34M-E">>,0,0},
{'queue.declare_ok',
<<"amq.gen-wmkOrALHBIj6Ot6ZuZZOQJ">>,0,0},
{'queue.declare_ok',
<<"amq.gen-wX2NmwMHBeDaKLvoZgJhEh">>,0,0},
{'queue.declare_ok',
<<"amq.gen-gcvScDp-RFMVwxWpyWjI-9">>,0,0},
{'queue.declare_ok',
<<"amq.gen-Q4CS7jNu3cde0RNdVdO3PJ">>,0,0},
{'queue.declare_ok',
<<"amq.gen-QKNrG8IJPVvfAlLukq38x_">>,0,0},
{'queue.declare_ok',
<<"amq.gen-wqJ2V1HQDaJjOzRDhv8gT4">>,0,0},
{'queue.declare_ok',
<<"amq.gen-AYeZiuNYsFOUMVw6xKcZh4">>,0,0},
{'queue.declare_ok',
<<"amq.gen-AJDqT2h2fq9cZOsVbNESi0">>,0,0}]
in function amqp_example:test/0 (src/amqp_example.erl, line 16)
yus-iMac:~ yuchen$ sudo rabbitmqctl list_queues
Password:
Listing queues ...
amq.gen-Q4CS7jNu3cde0RNdVdO3PJ 0
amq.gen-QKNrG8IJPVvfAlLukq38x_ 0
amq.gen-AqAaMLydgMf43y_XoYSdq5 0
amq.gen-AJDqT2h2fq9cZOsVbNESi0 0
amq.gen-wqJ2V1HQDaJjOzRDhv8gT4 0
amq.gen-AYeZiuNYsFOUMVw6xKcZh4 0
amq.gen-wzvWzxXo2MJVZsyrwfzM8A 0
amq.gen-A75g--nsvheNbwYMr34M-E 0
amq.gen-gcvScDp-RFMVwxWpyWjI-9 0
amq.gen-wX2NmwMHBeDaKLvoZgJhEh 0
amq.gen-wmkOrALHBIj6Ot6ZuZZOQJ 0
...done.
答案 0 :(得分：0)
客户端应创建一个具有特定名称的队列，并确保将其设置为autodelete。这样，客户端将不会重新创建预先存在的队列。每个客户端都会创建自己的特定队列，因为每个客户端都会相应地命名其队列。
答案 1 :(得分：0)
好的。现在我们假设你有一个Erlang Rabbitmq client的正确设置。使用用户指南 here 。
1。通用RABBITMQ连接器
-module(rabbit_utils).
-compile(export_all).
-define(RABBIT_SERVER,"localhost").
-define(RABBIT_PORT,9001).
-record(pipe,{connection,channel}).
create_pipe()->
try amqp_connection:start(#amqp_params_network{host = ?RABBIT_SERVER,
port = RABBIT_PORT}) of
{ok, Connection} ->
try amqp_connection:open_channel(Connection) of
{ok,Channel} ->
#pipe{
connection = Connection,
channel = Channel
};
_ -> amqp_connection:close(Connection),error
catch
_:_ -> amqp_connection:close(Connection),error
end;
_ -> error
catch
_:_ -> error
end.
close_pipe(Channel,Connection)->
try amqp_channel:close(Channel) of _ -> ok catch _:_ -> ok end,
try amqp_connection:close(Connection) of _ -> ok catch _:_ -> ok end,
ok.
我们会继续注意到，我会继续创建管道并关闭管道。这是因为，在erlang rabbitmq client的最新版本中，连接和通道变量是Erlang进程。每当某些内容未按计划在此库中进行时，这些进程将在运行时死亡。出于这个原因，我在try ... catch ... end代码块中捕获了大多数代码。如果您正在使用gen_servers，那么，将它们设为trap_exit = true，然后将它们链接到RabbitMQ客户端进程（连接和通道）。因此，每当连接中断时，Connection进程就会死亡，将其捕获到gen_server中，然后尝试另一个连接，如果失败，也许你可以拥有许多RABBITMQ个服务器{{1 }} 至。概念很深入，但让我们继续。
2。 Exchange管理器
这确保fail over服务器上存在交换。交换必须是RABBITMQ。我假设我们需要持久的交流和队列。持久交换和队列的一个优点是您只需创建一次，即使重新启动RABBITMQ服务，它也会使用这些交换和队列进行引导。
ensure_exchange_exists(Exchange)->
case create_pipe() of
error -> error;
#pipe{connection = Connection,channel = Channel} ->
RandomQueue = list_to_binary(guid()),
#'queue.declare_ok'{} = amqp_channel:call(Channel,#'queue.declare'{queue = RandomQueue}),
Binding = #'queue.bind'{queue = RandomQueue,exchange = Exchange,
routing_key = <<"testing">>},
try amqp_channel:call(Channel, Binding) of
#'queue.bind_ok'{} ->
Delete = #'queue.delete'{queue = RandomQueue},
#'queue.delete_ok'{} = amqp_channel:call(Channel, Delete),
close_pipe(Channel,Connection),
ok;
_ ->
close_pipe(Channel,Connection),
create_exchange(Exchange,Server)
catch
_R:_T ->
close_pipe(Channel,Connection),
create_exchange(Exchange,Server)
end;
_ -> error
end.
create_exchange(Exchange)->
case create_pipe() of
error -> error;
#pipe{connection = Connection,channel = Channel} ->
Exc = #'exchange.declare'{exchange = Exchange,durable = true},
try amqp_channel:call(Channel,Exc) of
#'exchange.declare_ok'{} -> ok;
_ -> close_pipe(Channel,Connection),error
catch
_:_ -> close_pipe(Channel,Connection),error
end
end.
guid()->
random:seed(now()),
MD5 = erlang:md5(term_to_binary([random:uniform(7677771995517),{self(),time(),node(), now(), make_ref()}])),
MD5List = lists:nthtail(2, binary_to_list(MD5)),
F = fun(N) -> f("~2.16.0B", [N]) end,
L = [F(N) || N <- MD5List],
lists:flatten(L).
f(S)-> f(S,[]).
f(S,Args) -> lists:flatten(io_lib:format(S, Args)).
3。队列管理器
对于大型系统，我们发现使用一个交换机（或几个交换机）更容易，但拥有与系统需要交互的队列一样多的队列。想象一下，在集群中，每个系统都有一个队列，其他系统在需要从该系统询问某些内容时发送消息。此外，当系统从另一个系统获取请求时，它会通过将答案发送到该系统的队列来回复该请求。通过良好的消息格式协议，它可以实现系统识别，区分来自回复，时间戳，系统ping，远程过程调用的请求，e.t.c最终会在群集中显示消息路由器。在最近的一个项目中，我们提出了一个远程过程协议，使用binary作为消息格式。系统可以通过AMQP接口调用方法并将参数传递给远程系统。我不能在这里详细介绍，但只是知道，我们现在依赖它JSON Genuis。{
无论如何，我们首先需要确定一个队列存在，然后，如果存在，检查它是否绑定到我们的交换。我们走吧 ！！
ensure_queue(Queue,Exchange)->
#pipe{connection = Connection,channel = Channel} = create_pipe(), Get = #'basic.get'{queue = Queue}, Sure = try amqp_channel:call(Channel, Get) of #'basic.get_empty'{} -> queue_exists;
{#'basic.get_ok'{}, _Content} -> queue_exists; _ -> queue_missing catch _EE:_EE2 -> queue_missing end, close_pipe(Channel,Connection), case Sure of queue_exists -> ensure_bound(Queue,Exchange); queue_missing -> create_queue_and_ensure_bound(Queue,Exchange) end.
ensure_bound(Queue,Exchange)->
#pipe{connection = Connection,channel = Channel} = create_pipe(), B1 = #'queue.bind'{queue = Queue,exchange = Exchange,routing_key = Queue}, try amqp_channel:call(Channel, B1) of #'queue.bind_ok'{} -> close_pipe(Channel,Connection), ok; _OtherErr -> error catch _ET:_EY -> error end.
create_queue_and_ensure_bound(Queue,Exchange)-> #pipe{connection = Connection,channel = Channel} = create_pipe(), TheQ = #'queue.declare'{queue = Queue,durable = true}, try amqp_channel:call(Channel,TheQ) of #'queue.declare_ok'{} -> Binding = #'queue.bind'{queue = Queue,exchange = Exchange,routing_key = Queue}, try amqp_channel:call(Channel, Binding) of #'queue.bind_ok'{} -> close_pipe(Channel,Connection), error; _Other2 -> close_pipe(Channel,Connection), error catch _ER11:_ER22 -> close_pipe(Channel,Connection), error end; _Other -> close_pipe(Channel,Connection), error catch _ER1:_ER2 -> close_pipe(Channel2,Connection2), error end.
100%服务器，并且您在所有RABBITMQ服务器上安装了所有相同的交换和队列，这样如果一台服务器丢失，其他服务器可用于继续服务。