scaling Node.js apps
with message queues

Kyle Anderson

• Full-Stack JavaScript Developer (Back-End emphasis)
• JS Dev since 2014, professionally since 2016
• Video Nerd for PDXNode
• Studied Media & Journalism @ Northern Arizona University

Agenda

1. Horizontal vs. Vertical Scaling
2. The Master/Worker Model
3. Queue Concepts
4. Demo
5. Queue Implementations

First: Why?

• Improved Speed for Batch Jobs
• Added Resiliency
• Avoids Resource Limitations

Image Source: https://stackoverflow.com/questions/51839398/heap-out-of-memory-in-mongodb-and-node-js

Horizontal vs. Vertical Scaling

CPU/RAM

CPU/RAM

CPU/RAM

CPU/RAM

Vertical Scaling

One Machine, Add More Resources

Horizontal Scaling

Multiple Machines, Add More Machines

CPU/RAM

CPU/RAM

CPU/RAM

CPU/RAM

How does Node.js scale?

The Master/Worker Model

Master

Worker

Message Queue

Worker

Worker

The Master/Worker Model

Master 1

Worker

Message Queue

Worker

Worker

Master 2

Queue Concepts

🔃First/Last In/Out 🔃

🔓Locks 🔒

💦Back Pressure🌊

📨Ordered Messages📩

💀Dead-Letter Queue ☠

Demo

Production Example

Production Example

Source:  ​https://www.reddit.com/r/redditdev/comments/6hudbt/what_is_the_journey_of_a_vote_through_reddits/

Reddit uses queues to process votes. Simplified explanation:

1. Update arrow graphic
2. POST /api/vote
3. Cache is updated (Vote persists visually)
4. Vote is added to RabbitMQ
5. Queue workers update databases (Vote is counted)

Queue Implementations

Bull

Cons

• Proprietary protocol
• Relatively Young Product
• Node.js Only

Pros

• User-Friendly
• Low Maintenance Overhead
• Full-featured

Queue Implementations

RabbitMQ

* Disclaimer: I have only researched this product and have not yet worked with it.

Cons

• Higher Maintenance Overhead
• Less User-Friendly

Pros

• Uses standard protocols (AMQP)
• Multiple Languages
• Well-Established (since late 2000s)

Queue Implementations

AWS Simple Queue Service (SQS)

Cons

• Vendor Lock-In
• Proprietary API
• Pay-as-you-go

Pros

• Excellent for Serverless
• No Maintenance Overhead
• Pay-as-you-go

* Disclaimer: I have only researched this product and have not yet worked with it.

Summary

1. Horizontal vs. Vertical Scaling
2. The Master/Worker Model
3. Queue Concepts
4. Demo
5. Queue Implementations

@ Me

https://kyleanderson.us

@KAndersonUS

Everything Else ➡
(keybase.io/kandersonus)