amqp.connect is not able to maintain connection alive forever - node.js

Question

My code is as shown below :
rabbitmq.js
const connectRabbitMq = () => {
amqp.connect(process.env.CLOUDAMQP_MQTT_URL, function (err, conn) {
if (err) {
console.error(err);
console.log('[AMQP] reconnecting in 1s');
setTimeout(connectRabbitMq, 1);
return;
}
conn.createChannel((err, ch) => {
if (!err) {
console.log('Channel created');
channel = ch;
connection = conn;
}
});
conn.on("error", function (err) {
if (err.message !== "Connection closing") {
console.error("[AMQP] conn error", err.message);
}
});
conn.on("close", function () {
console.error("[AMQP] reconnecting");
connectRabbitMq();
});
})
};
const sendMessage = () => {
let data = {
user_id: 1,
test_id: 2
};
if (channel) {
channel.sendToQueue(q, new Buffer(JSON.stringify(data)), {
persistent: true
});
}
else {
connectRabbitMq(() => {
channel.sendToQueue(q, new Buffer(JSON.stringify(data)), {
persistent: true
});
})
}
};
const receiveMessage = () => {
if (channel) {
channel.consume(q, function (msg) {
// ch.ack(msg);
console.log(" [x] Received %s", msg.content.toString());
});
}
else {
connectRabbitMq(() => {
channel.consume(q, function (msg) {
// ch.ack(msg);
console.log(" [x] Received %s", msg.content.toString());
});
})
}
}
scheduler.js
let cron = require('node-cron');
const callMethodForeverRabbitMq = () => {
cron.schedule('*/1 * * * * *', function () {
rabbitMqClientPipeline.receiveMessage();
});
};
app.js
rabbitmq.sendMessage();
now what happens here is , the code is not able to maintain the connection alive forever . so is there any way I can keep it alive forever ?

Answer 1

I am not sure if you are using Promise api or callback API.
With Promise API you can do it like this:
const amqp = require('amqplib');
const delay = (ms) => new Promise((resolve => setTimeout(resolve, ms)));
const connectRabbitMq = () => amqp.connect('amqp://127.0.0.1:5672')
.then((conn) => {
conn.on('error', function (err) {
if (err.message !== 'Connection closing') {
console.error('[AMQP] conn error', err.message);
}
});
conn.on('close', function () {
console.error('[AMQP] reconnecting');
connectRabbitMq();
});
//connection = conn;
return conn.createChannel();
})
.then(ch => {
console.log('Channel created');
//channel = ch;
})
.catch((error) => {
console.error(error);
console.log('[AMQP] reconnecting in 1s');
return delay(1000).then(() => connectRabbitMq())
});
connectRabbitMq();
With callback API like this:
const amqp = require('amqplib/callback_api');
const connectRabbitMq = () => {
amqp.connect('amqp://127.0.0.1:5672', function (err, conn) {
if (err) {
console.error(err);
console.log('[AMQP] reconnecting in 1s');
setTimeout(connectRabbitMq, 1000);
return;
}
conn.createChannel((err, ch) => {
if (!err) {
console.log('Channel created');
//channel = ch;
//connection = conn;
}
});
conn.on("error", function (err) {
if (err.message !== "Connection closing") {
console.error("[AMQP] conn error", err.message);
}
});
conn.on("close", function () {
console.error("[AMQP] reconnecting");
connectRabbitMq();
});
})
};
connectRabbitMq();
UPDATE new code with request buffering
const buffer = [];
let connection = null;
let channel = null;
const connectRabbitMq = () => {
amqp.connect('amqp://127.0.0.1:5672', function (err, conn) {
if (err) {
console.error(err);
console.log('[AMQP] reconnecting in 1s');
setTimeout(connectRabbitMq, 1000);
return;
}
conn.createChannel((err, ch) => {
if (!err) {
console.log('Channel created');
channel = ch;
connection = conn;
while (buffer.length > 0) {
const request = buffer.pop();
request();
}
}
});
conn.once("error", function (err) {
channel = null;
connection = null;
if (err.message !== "Connection closing") {
console.error("[AMQP] conn error", err.message);
}
});
conn.once("close", function () {
channel = null;
connection = null;
console.error("[AMQP] reconnecting");
connectRabbitMq();
});
})
};
const sendMessage = () => {
let data = {
user_id: 1,
test_id: 2
};
if (channel) {
channel.sendToQueue(q, new Buffer(JSON.stringify(data)), {
persistent: true
});
}
else {
buffer.push(() => {
channel.sendToQueue(q, new Buffer(JSON.stringify(data)), {
persistent: true
});
});
}
};
const receiveMessage = () => {
if (channel) {
channel.consume(q, function (msg) {
// ch.ack(msg);
console.log(" [x] Received %s", msg.content.toString());
});
}
else {
buffer.push(() => {
channel.consume(q, function (msg) {
// ch.ack(msg);
console.log(" [x] Received %s", msg.content.toString());
});
})
}
};
There are edge cases where this code won't work - for example it won't reestablish queue.consume unless it's called explicitly. But overall this hopefully gives you idea on how to implement proper recovery...