如何从amqplib库中为node.JS使用channel.assertQueue函数？

Question

我正在使用RabbitMQ和Node.JS开发一个消息传递应用程序.我为此目的使用amqplib.我是Node.JS的新手,并且在理解amqplib的语法方面遇到了一些困难.例如,有一个声明队列的函数,即

channel.assertQueue([queue, [options, [function(err, ok) {...}]]]);

我在过去的2-3天里一直在提这个,但我仍然不清楚这些 - > err和ok.如何使用这些参数？

一个例子将非常感激.

Answer 1

ampqlib github页面有一些关于如何使用库的示例,使用回调或promise.

我复制了他们的第一个例子,并添加了一些注释来解释发生了什么.

可能值得检查他们的教程示例,这是在官方RabbitMQ教程之后.

var amqp = require('amqplib/callback_api');
var q = 'tasks';

// connects to rabbitmq
amqp.connect('amqp://localhost', function(err, conn) {
    // this function will be called when the connection is created
    // `err` will contain the error object, if any errors occurred
    // `conn` will contain the connection object

    if (err != null) bail(err); // calls `bail` function if an error occurred when connecting
    consumer(conn); // creates a consumer
    publisher(conn); // creates a publisher
});

function bail(err) {
    console.error(err);
    process.exit(1);
}

// Publisher
function publisher(conn) {
    conn.createChannel(on_open); // creates a channel and call `on_open` when done
    function on_open(err, ch) {
        // this function will be called when the channel is created
        // `err` will contain the error object, if any errors occurred
        // `ch` will contain the channel object

        if (err != null) bail(err); // calls `bail` function if an error occurred when creating the channel
        ch.assertQueue(q); // asserts the queue exists
        ch.sendToQueue(q, new Buffer('something to do')); // sends a message to the queue
    }
}

// Consumer
function consumer(conn) {
    var ok = conn.createChannel(on_open); // creates a channel and call `on_open` when done
    function on_open(err, ch) {
        // this function will be called when the channel is created
        // `err` will contain the error object, if any errors occurred
        // `ch` will contain the channel object

        if (err != null) bail(err); // calls `bail` function if an error occurred when creating the channel
        ch.assertQueue(q); // asserts the queue exists
        ch.consume(q, function(msg) { //consumes the queue
            if (msg !== null) {
                console.log(msg.content.toString()); // writes the received message to the console
                ch.ack(msg); // acknowledge that the message was received
            }
        });
    }
}