Microservices Architectures - Introduction to Auto Scaling

In this article, we focus our attention on the Dynamic Scaling or Auto Scaling. Why do we need applications that can auto scale?

You will learn

  • What is Auto or Dynamic Scaling?
  • Why is Dynamic Scaling important in a microservices context?
  • How can you implement Dynamic Scaling in Cloud?

Cloud and Microservices Terminology

This is the fifth article in a series of six articles on terminology used with cloud and microservices:

Load On Applications Varies

Load on your applications vary depending on time of the day, the day of the month or the month of the year.

Take for instance, amazon.com. It has very high loads during Thanks Giving Period, up to 20 times the normal load. However, during the major sports events such as Superbowl or a Football World Cup, the traffic could be considerably lesser - because every body is busy watching the event.

How can you setup infrastructure for applications to manage varying loads?

It is quite possible that the infrastructure needed to handle 10x the load, is ten times that needed to handle 1x the load.

If you have on premise infrastructure, you need a large infrastructure in place to handle peak load.

During periods with lesser load, a lot of infrastructure would be sitting idle.

Cloud To The Rescue

That’s where cloud comes into picture. With cloud, you can request more resources when the load is high and give them back to the cloud when you have less load.

This is called Scale Out (create more instances as load increases) and Scale In (reduces instances as load goes down)

How do you build applications that are cloud enabled - applications that work well in the cloud?

That’s where a microservices architecture comes into picture.

Introducing Auto Scaling Example

Building your application using microservices enables you to increase the number of microservice instances during high load, and reduce them during less load.

Consider the following example of a CurrencyConversionService:

image info

image info

The CurrencyConversionService talks to the ForexService. The ForexService is concerned with calculating how many INR can result from 1 USD, or how many INR can result from 1 EUR.

The CurrencyConversionService takes a bag of currencies and amounts, and produce the total amount in a currency of your choice. For example, it will tell the total worth in INR of 10 EUR and 25 USD.

The ForexService might also be consumed from a number of other microservices.

Scaling Infrastructure To Match Load

The load on ForexService might be different from the load on CurrencyConversionService. You might need to have different number of instances of CurrencyConversionService and ForexService. For example, there may be two instances of the CurrencyConversionService, and five instances of the ForexService:

image info

image info

At a later point in time, the load on CurrencyConversionService could be low, needing just two instances. On the other hand, a much higher load on ForexService could need 50 instances. The requests coming in from the 2 instances of CurrencyConversionService are distributed across the 50 instances of the ForexService.

That in essence, is the requirement for auto scaling - dynamically changing number of microservice instances, and evenly distributing the load across them.

Implementing Auto Scaling

There are a few important concepts involved in implementing auto scaling. The following sections discuss them in some detail.

Naming Server

Naming servers enables something called location transparency. Every microservice registers with the naming service. Any microservice that needs to talk to another microservice, will ask the naming server for its location.

Whenever a new instance of CurrencyConversionService or ForexService comes up, it registers with the naming server. image info

When CurrencyConversionService wants to talk to ForexService, it asks the naming server for available instances.

Implementing Location Transparency

CurrencyConversionService knows that there are five instances of the ForexService.

How does it distribute the load among all these instances?

That’s where a load balancer comes into the picture.

A popular client side load balancing framework is Ribbon. image info

Let’s look at a diagram to understand whats happening:

image info

As soon as any instance of CurrencyConversionService or ForexService comes up, it registers itself with the naming server. If the CCSInstance2 wants to know the URL of ForexService instances, it again talks to the naming server. The naming server responds with a list of all instances of the ForexService - FSInstance1 and FSinstance2, and their corresponding URLs.

The Ribbon load balancer does a round-robin among the ForexService instances to balance out the load among the instances.

Ribbon offers wide variety of load balancing algorithms to choose from.

When to increase and decrease instances?

There is one question we did not really talk about.

How do we know when to increase or decrease the number of instances of a microservices?

That is where application monitoring and container (Docker) management (using Kubernetes) comes into the picture.

image info

An application needs to be monitored to find out how much load it has. For this, the application has to expose metrics for us to track the load.

You can containerize each microservice using Docker and create an image.

Kubernetes has the capability to manage containers. Kubernetes can configured to auto scale based on the load. Kubernetes can identify the application instances, monitor their loads, and automatically scale up and down.

Do check out our video on this:

image info


In this article, we talked about auto scaling. We look at important parts of implementing auto scaling - naming server, load balancer, containers (Docker) and container orchestration (Kubernetes).

10 Step Reference Courses

Image Image Image Image Image

in28Minutes is creating amazing solutions for you to learn full stack and the cloud - Docker, Kubernetes, AWS, React, Angular etc. Click here for the complete catalogue of 30 Courses.

Related Posts

Spring Boot Tutorials for Beginners

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. This resources will help you learn and gain expertise at Spring Boot.

Spring and Spring Boot Video Tutorials for Beginners

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. Here's a list of video tutorials and courses for you

Software Design - Separation Of Concerns - with examples

Software architects and programmers love having Seperation of Concerns. What is it? Why is it important? Let's get started.

Object Oriented Software Design - Solid Principles - with examples

Software design is typically complex. Object oriented design takes it to the next level. There are a number of design patterns and other stuff to be aware of. Can we make things simple? What are the goals to aim for when you are doing object oriented design? SOLID Principles is a great starting point for Object Oriented Design.

Software Design - Open Closed Principle - with examples

Open Closed Principle is one of the SOLID Principles. You want your code to be easily extended. How do you achieve it with minimum fuss? Let's get started.

Software Design - What is Dependency Inversion Principle?

Dependency Inversion Principle is one of the important SOLID Principles. Dependency Inversion Principle is implemented by one of the most popular Java frameworks - Spring. What is it all about? How does it help you design good applications?

Introduction to Four Principles Of Simple Design

With agile and extreme programming, the focus is on keeping your design simple. How do you keep your design simple? How do you decide whether your code is good enough?

Software Design - Single Responsibility Principle - with examples

For me, Single Responsibility Principle is the most important design principle. What is Single Responsibility Principle? How do you use it? How does it help with making your software better? Let's get started.

REST API Best Practices - With Design Examples from Java and Spring Web Services

Designing Great REST API is important to have great microservices. How do you design your REST API? What are the best practices?

Designing REST API - What is Code First Approach?

Designing Great REST API is important to have great microservices. Code First approach focuses on generating the contract from code. Is it the best possible approach?