我从http://www.rabbitmq.com/tutorials/tutorial-six-java.html中提取了这个例子,从RPCClient
中添加了一个RPC调用,并在标准输出中添加了一些日志记录。因此,当执行第二次调用时,rabbitmq使用了错误的相关ID的消费者,这不是预期的行为。是窃听器还是我搞错了?
RPC服务器:
package com.foo.rabbitmq;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Consumer;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Envelope;
import java.io.IOException;
import java.util.concurrent.TimeoutException;
public class RPCServer {
private static final String RPC_QUEUE_NAME = "sap-consume";
private static int fib(int n) {
if (n ==0) return 0;
if (n == 1) return 1;
return fib(n-1) + fib(n-2);
}
public static void main(String[] argv) {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
factory.setPort(5672);
Connection connection = null;
try {
connection = factory.newConnection();
final Channel channel = connection.createChannel();
channel.queueDeclare(RPC_QUEUE_NAME, false, false, false, null);
channel.basicQos(1);
System.out.println(" [x] Awaiting RPC requests");
Consumer consumer = new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
AMQP.BasicProperties replyProps = new AMQP.BasicProperties
.Builder()
.correlationId(properties.getCorrelationId())
.build();
String response = "";
try {
String message = new String(body,"UTF-8");
int n = Integer.parseInt(message);
System.out.println(" [.] fib(" + message + ")");
response += fib(n);
}
catch (RuntimeException e){
System.out.println(" [.] " + e.toString());
}
finally {
channel.basicPublish( "", properties.getReplyTo(), replyProps, response.getBytes("UTF-8"));
channel.basicAck(envelope.getDeliveryTag(), false);
// RabbitMq consumer worker thread notifies the RPC server owner thread
synchronized(this) {
this.notify();
}
}
}
};
channel.basicConsume(RPC_QUEUE_NAME, false, consumer);
// Wait and be prepared to consume the message from RPC client.
while (true) {
synchronized(consumer) {
try {
consumer.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
} catch (IOException | TimeoutException e) {
e.printStackTrace();
}
finally {
if (connection != null)
try {
connection.close();
} catch (IOException _ignore) {}
}
}
}
RPCCLient:
package com.bar.rabbitmq;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Envelope;
import java.io.IOException;
import java.util.UUID;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeoutException;
public class RPCClient {
private Connection connection;
private Channel channel;
private String requestQueueName = "sap-consume";
private String replyQueueName;
public RPCClient() throws IOException, TimeoutException {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
factory.setPort(5672);
connection = factory.newConnection();
channel = connection.createChannel();
replyQueueName = channel.queueDeclare().getQueue();
}
public String call(String message) throws IOException, InterruptedException {
final String corrId = UUID.randomUUID().toString();
AMQP.BasicProperties props = new AMQP.BasicProperties
.Builder()
.correlationId(corrId)
.replyTo(replyQueueName)
.build();
channel.basicPublish("", requestQueueName, props, message.getBytes("UTF-8"));
final BlockingQueue<String> response = new ArrayBlockingQueue<String>(1);
channel.basicConsume(replyQueueName, true, new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
if (properties.getCorrelationId().equals(corrId)) {
System.out.println("Correlation Id" + properties.getCorrelationId() + " corresponds to expected one.");
response.offer(new String(body, "UTF-8"));
} else {
System.out.println("Correlation Id" + properties.getCorrelationId() + " doesn't correspond to expected one " + corrId);
}
}
});
return response.take();
}
public void close() throws IOException {
connection.close();
}
public static void main(String[] argv) {
RPCClient rpc = null;
String response = null;
try {
rpc = new RPCClient();
System.out.println(" [x] Requesting fib(30)");
response = rpc.call("30");
System.out.println(" [.] Got '" + response + "'");
System.out.println(" [x] Requesting fib(40)");
response = rpc.call("40");
System.out.println(" [.] Got '" + response + "'");
} catch (IOException | TimeoutException | InterruptedException e) {
e.printStackTrace();
} finally {
if (rpc != null) {
try {
rpc.close();
} catch (IOException _ignore) {
}
}
}
}
}
2条答案
按热度按时间rmbxnbpk1#
是的,你在教程代码中发现了一个bug。我已经在这里打开了一个pull request来修复它,你也可以找到对发生的事情的解释:
https://github.com/rabbitmq/rabbitmq-tutorials/pull/174
k7fdbhmy2#
这个例子很简单:它使用一个队列用于应答。通过发送第二个请求,您向应答注册了一个新的消费者,但第一个请求的消费者仍然在侦听,实际上 * 窃取了第二个请求的响应 *。这就是为什么客户端似乎使用相同的相关ID。
我们updated the client code为每个请求使用独占的自动删除队列。这个队列将被服务器自动删除,因为它的唯一消费者在收到响应后被取消订阅。这有点复杂,但更接近现实世界的场景。
注意,使用RabbitMQ处理回复队列的最佳方法是使用direct reply-to。这使用比真实的队列更轻的伪队列。我们在教程中没有提到直接回复,以使其尽可能简单,但这是生产中使用的首选功能。