RabbitMQ have an exclusive consumer consume message serially - node.js

Question

I have a scenario that on a given topic I need to consume each message one by one, do some async task and then consume the next one. I am using rabbitmq and amqp.node.
I was able to achieve this with a prefetch of 1. Which of course is not an actual solution since this would lock the whole channel and the channel have multiple topics.
So far this is my producer:
const getChannel = require("./getChannel");
async function run() {
const exchangeName = "taskPOC";
const url = "amqp://queue";
const channel = await getChannel({ url, exchangeName });
const topic = "task.init";
let { queue } = await channel.assertQueue(topic, {
durable: true
});
const max = 10;
let current = 0;
const intervalId = setInterval(() => {
current++;
if (current === max) {
clearInterval(intervalId);
return;
}
const payload = JSON.stringify({
foo: "bar",
current
});
channel.sendToQueue(queue, Buffer.from(payload), { persistent: true });
}, 3000);
}
run()
.then(() => {
console.log("Running");
})
.catch(err => {
console.log("error ", err);
});
And this is my consumer
const getChannel = require("./getChannel");
async function run() {
const exchangeName = "taskPOC";
const url = "amqp://queue";
const channel = await getChannel({ url, exchangeName });
channel.prefetch(1);
const topic = "task.init";
const { queue } = await channel.assertQueue(topic, {
durable: true
});
channel.bindQueue(queue, exchangeName, topic);
let last = new Date().getTime();
channel.consume(
queue,
msg => {
const now = new Date().getTime();
console.log(
" [x] %s %s:'%s' ",
msg.fields.routingKey,
Math.floor((now - last) / 1000),
msg.content.toString()
);
last = now;
setTimeout(function() {
channel.ack(msg);
}, 10000);
},
{ exclusive: true, noAck: false }
);
}
run()
.then(() => {
console.log("Running");
})
.catch(err => {
console.log("error ", err);
});
Is there any way on RabbitMQ to do that or I would need to handle this on my app?
Thanks.

Answer 1

You can use the consumer prefetch setting (see https://www.rabbitmq.com/consumer-prefetch.html). In the case of amqp node, you set this option using the prefetch function:
channel.prefetch(1, false); // global=false
In this case, each consumer on the channel will have a prefetch of 1. If you want to have different configurations for each consumer, you should create more channels.
Hope this helps.