The traditional way of building apps makes them large and complex. To keep the competitive advantage and innovate business development should be fast and agile.
Microservices became the developers’ answer to changing market requirements. It improves the scalability and maintainability of complex systems. But can we claim it a technological breakthrough that makes previous architectural approaches obsolete?
Let’s find out what microservices is: panacea or just another design pattern, define its workflow and the best strategies to move to this type of app development architecture.
What are microservices in Java
The evolution of best-practice architectural principles — microservices are concerned to be an approach to developing an app as a complex of independent modules.
Each of them provides a single business capability with lightweight mechanisms like API:
It consists of 8 parts:
Client (mobile phone, tablet, browser, etc.)
Identity provider for services’ security
CDN for static content delivery
API for clients’ and services’ system parts communication
Management for services placing and balance across nodes, identifying failures
Service Discovery for maintaining a list of services and their nodes location
Service is a microservice that provides some specific features
Remote services like REST, web service, etc. for any of your microservice needs
Microservices based applications have certain characteristics:
Can be written in different programming languages.
Make an app simple to scale and manage. Different app parts can be scaled to a number of resources.
Use different data storage technologies like clouds and data centres.
Can be updated or deleted individually from the rest of the app.
Can be managed by independent developers groups without impacting each other's work.
The scheme of an app architecture with a set of separated services with its teams. Each of them has a clear, non-overlapping zone of responsibilities.
Are separated by domains and functionalities.
Use their load balancer.
Communicate with each other through a stateless server like Message Bus or REST.
Have their special path of communication to perform operational capabilities such as monitoring or automation individually.
Are communicated to clients via API.
How microservices communicate with each other
The microservices' idea is that when the app is broken down into independent modules that work seamlessly together it’s simpler to develop, manage, and fix.
Youngsters developers are looking for simple technologies, no pro to support really complicated systems.
How microservices work. Examples
The benefits of this architecture style were appreciated by business sharks like Walmart, Spotify, eBay, Uber, PayPal, Twitter, etc. The accelerating rate of companies’ growth requires business agility, so they transformed and moved to microservices.
Amazon followed their example because its old, two-tiered architecture couldn’t cope with the rising number of system calls from a variety of applications.
Having started as a monolith Netflix evolved to SOA for the same reason. Today its API receives more than 1 000 000 000 calls per day from 800 different apps.
Let’s have a closer look at the microservices architecture. For example, a case of an event agency ticket service based on microservices.
When clients buy a ticket for some conference, they see only the website. But, behind the scenes, the event agency application has a service for accounting, payments, ticket sales service, service for conference presentations schedule.
Each of them consists of other services like the last one that contains microservice for registering speakers and scheduling the list of presentations.
All of them have specific functions but at the same time, they are connected like microservices for accounting and scheduling. At first glance, there isn’t any connection between them. However, everyone who has bought a ticket should get its badge with their name and report timetable on the back. So, they do. Printing the badges is a bounded context of these two isolated microservices.
When a person buys a ticket system sends an event to the accounting microservice for user data, to the presentation scheduling part for a conference program, to the payment system to proceed with the purchase.
Due to the module's isolation, there is no problem if one of the microservice is down. The other will continue functioning.
If you are interested in moving to this architectural style, you should be ready to face the difficulties it brings.
Microservices advantages bring new challenges
Despite all the benefits of this architectural style, there is a list of challenges young developers teams face when it comes to implementing microservices in the system. It could be difficulties from the technical as well as classical communication problems.
Starting a microservice app or transition to microservices needs careful planning and a professional team of developers and managers.
Different technological bases complicate the movement from one database implementation type to another with the given tech requirements.
Skills. When a developer with some set of coding skills switches teams and goes to the service based on other languages, it takes more time to accommodate.
Management. Due to the increasing number of services, it becomes difficult to integrate and manage the whole product. For example, different schedules can be the reason for the resource conflict between development teams that can slow-down the start of the project.
Informational barriers between separated teams can result in duplication of effort.
Communication between the multiple services requires developers to put extra efforts to make the mechanism work.
The moving parts of the microservices architecture have many potential errors that lead to the usage of graceful degradation approaches.
Testing. As the focus of the independent team is its microservice, big projects lack a complex approach to integration and testing. It could be difficult to get all the necessary information out of some log when each of the microservices has a special logging format.
Migration. Due to the missing transaction management while domain decomposition moving to microservices causes real issues.
Microservices architecture: Where to start
Playing microservices’ game when there are three developers in your team is a long story with no happy ending mostly. You should understand that this architecture is about heavy apps with multiple functions and big dev teams.
If you want to deploy an app that fit these basic requirements, start with a monolith. It’s easier to decompose. The development of an app from the microservice stretch is more complicated but also real. However, you can't do vice versa and collect microservices into a monolith (if needed).
Starting from a monolith gives our team time to understand the big picture of the product’s future and comfort space for refactoring, tracking classes, etc.
The microservice division comes when you have a clear vision of the product, which needs time.
There is an app with 40 microservice parts. To add a new feature and its testing took about 3 hours. The movement to a monolithic repository (the data storage type) reduced the time of testing up to 15 minutes. 3 hours and 15 minutes — great difference, isn’t it?
That’s only an example. There is no exact answer on how to start a microservice app development: a monolith separation or directly from microservices. It’s up to product-specific, budget, and team.
But what if there is a working monolith app you want to transform to microservices?
Migration from monolith to microservices strategies
3 level architecture with interface, data, and microservice layers. Adding a microservice layer between an app desktop interface and its backend to replace some functionality. On the proof of concept, stage users don't see the change and the app doesn't change. When the app logic is under 100% microservice control, the web-oriented layer development starts.
Modules replacement strategy. You choose a group of people to test microservice-based functionality when the rest use the monolith app version. This new functionality uses an old database but processes it via a set of microservices. Thus, users went to the new app version by modules.
The movement to microservice relies on the company’s capabilities, desire, and need to adopt new technologies.
The future of microservice architecture style. When to apply
According to Google Trends the shift towards microservices continued:
One of the main reasons for this is that it perfectly fits the needs of Cloud Native, fast software development.
Despite the growing popularity, the architecture approach of breaking down the app into small components isn’t a silver bullet.
Microservices are a trend, but not a panacea. Sometimes it doesn't help: if you had a heavy app difficult to manage, after its decomposition to microservices you'll have a set of small but heavy functions still difficult to manage.
So when to use microservices architecture? When you need speed and flexibility
Practice shows that starting as small, companies choose it when monolithic structure stops meeting their needs like:
The development becomes too complicated and takes too much time.
Features updates stop the app workflow and lead to downtime.
There is a problem with continuous integration implementation.
The communication between teams is too complicated as well as the integration of a new developer into the project.
Product scaling requires redundant resources.
When you add the increasing complexity and communication requirements of SaaS apps, wearables, and the Internet of Things, microservices are the best option.
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