如何使用 Nodejs 在 RabbitMQ 中实现远程过程调用（RPC）

Question

所以我想获取一个 Json 并将其解析为对象，然后实现一个 RPC RabbitMQ 服务器，这样我就可以通过 RabbitMQ 将对象发送到服务器，然后对象将继续保存在本地数组和通用唯一 id 将告知对象存储的确切位置，并将通过 RPC 从该服务器返回到客户端。

官网展示了RabbitMQ中RPC的一些实现，在这里你可以找到他们的实现https://www.rabbitmq.com/tutorials/tutorial-six-javascript.html，在教程中他们发送一个数字，服务器将计算斐波那契数列并将结果返回给客户端。相反，我想发送一个对象，而不是一个数字，我想接收该对象的通用唯一 ID（uuid），我将其存储在我的程序的全局数组中，我更改了代码，以便它发送一个对象和返回 uuid 但它没有用。我会感谢你们的任何帮助

    //this is my server_rpc.js code : 
   const amqp = require('amqplib/callback_api');
   const uuid = require("uuid/v1");

  amqp.connect('here is the url: example: localhost', (err, conn) => {

   conn.createChannel( (err, ch) => {

    let q = 'rpc_queue';

    ch.assertQueue(q, {durable: false});

    ch.prefetch(10);

    console.log(' [x] Waiting RPC requests');

    ch.consume(q, function reply(msg) {

        console.log("corralation key is: ", msg.properties.correlationId);
        let n = uuid();


        console.log(" data received ",JSON.parse(JSON.stringify(msg.content.toString())));

        console.log("corralation key is: ", msg.properties.correlationId);

        ch.sendToQueue(msg.properties.replyTo, Buffer.from(n.toString()), {correlationId: msg.properties.correlationId});

        ch.ack(msg);
    });
});

});

    // and this is my client_rpc.js code : 
    const amqp = require('amqplib/callback_api');
    const uuid = require("uuid/v1");
     const express = require("express");

let data = {
"name" : "hil01", 
"region" : "weissach",
"ID" : "1",
"version" : "0.0.1"
           } 



      amqp.connect('url: example localhost ', (err, conn) => {

        conn.createChannel( (err, ch) => {

         ch.assertQueue('', {exclusive: true}, (err, q) => {

        var corr = generateUuid();
        var newHil = JSON.stringify(data);

        console.log(" [x] Requesting uuid for the registered HIL: ", newHil );

        console.log("corralation key is: ", corr);

        ch.consume(q.queue, function(msg) {

            if(msg.properties.correlationId == corr) {

                console.log(" [.] Got %s", msg.content.toString());
                setTimeout(() => { conn.close(); process.exit(0) }, 100);
            }
        }, {noAck: true});

        ch.sendToQueue('rpc_queue', Buffer.from(newHil, {correlationId: corr, replyTo: q.queue }));
    });
});

});

    //method to generate the uuid, later will be replaced with the real 
   uuid function 
      var generateUuid = () => Math.random().toString() + 
      Math.random().toString() + Math.random().toString()  ;

当我运行 server_rpc 时，应打印 [x] 等待请求，然后在单独的 cmd 中运行 client_rpc.js 然后发送对象，服务器执行并将 uuid 返回给客户端。

Answer 1

看来您需要的是直接回复 RPC 模式：您想要发送消息并获得响应。

这里是关于直接回复的 RabbitMQ 文档：https://www.rabbitmq.com/direct-reply-to.html

TL;TR

这是一个客户端和服务器的示例，可以直接使用：

https://github.com/Igor-lkm/node-rabbitmq-rpc-direct-reply-to

里面是什么

安装 RabbitMQ 后，您需要执行 2 个文件：

server.js

const amqp = require('amqplib');
const uuidv4 = require('uuid/v4');

const RABBITMQ = 'amqp://guest:guest@localhost:5672';

const open = require('amqplib').connect(RABBITMQ);
const q = 'example';

// Consumer
open
  .then(function(conn) {
    console.log(`[ ${new Date()} ] Server started`);
    return conn.createChannel();
  })
  .then(function(ch) {
    return ch.assertQueue(q).then(function(ok) {
      return ch.consume(q, function(msg) {
        console.log(
          `[ ${new Date()} ] Message received: ${JSON.stringify(
            JSON.parse(msg.content.toString('utf8')),
          )}`,
        );
        if (msg !== null) {
          const response = {
            uuid: uuidv4(),
          };

          console.log(
            `[ ${new Date()} ] Message sent: ${JSON.stringify(response)}`,
          );

          ch.sendToQueue(
            msg.properties.replyTo,
            Buffer.from(JSON.stringify(response)),
            {
              correlationId: msg.properties.correlationId,
            },
          );

          ch.ack(msg);
        }
      });
    });
  })
  .catch(console.warn);

client.js

const amqp = require('amqplib');
const EventEmitter = require('events');
const uuid = require('uuid');

const RABBITMQ = 'amqp://guest:guest@localhost:5672';

// pseudo-queue for direct reply-to
const REPLY_QUEUE = 'amq.rabbitmq.reply-to';
const q = 'example';

// Credits for Event Emitter goes to https://github.com/squaremo/amqp.node/issues/259

const createClient = rabbitmqconn =>
  amqp
    .connect(rabbitmqconn)
    .then(conn => conn.createChannel())
    .then(channel => {
      channel.responseEmitter = new EventEmitter();
      channel.responseEmitter.setMaxListeners(0);
      channel.consume(
        REPLY_QUEUE,
        msg => {
          channel.responseEmitter.emit(
            msg.properties.correlationId,
            msg.content.toString('utf8'),
          );
        },
        { noAck: true },
      );
      return channel;
    });

const sendRPCMessage = (channel, message, rpcQueue) =>
  new Promise(resolve => {
    const correlationId = uuid.v4();
    channel.responseEmitter.once(correlationId, resolve);
    channel.sendToQueue(rpcQueue, Buffer.from(message), {
      correlationId,
      replyTo: REPLY_QUEUE,
    });
  });

const init = async () => {
  const channel = await createClient(RABBITMQ);
  const message = { uuid: uuid.v4() };

  console.log(`[ ${new Date()} ] Message sent: ${JSON.stringify(message)}`);

  const respone = await sendRPCMessage(channel, JSON.stringify(message), q);

  console.log(`[ ${new Date()} ] Message received: ${respone}`);

  process.exit();
};

try {
  init();
} catch (e) {
  console.log(e);
}

你会得到一个结果，比如：