Microservices and microservices architecture
Learn the pros and cons of microservices and how they differ from monoliths.
Not very long ago, the preferred method of building software applications was a monolithic architecture, which was as a single, autonomous unit. This approach worked well for many developers until applications increased in complexity. When a modification to a small section of code is made in a monolithic system, it requires rebuilding the entire system, running tests on the entire system, and deploying an entirely new version of the application.
Then along came microservices, an approach that breaks down software systems into smaller units that are autonomously developed and deployed. The microservices architecture was driven by the DevOps movement that seeks to frequently deliver updates, like new features, bug fixes, and security improvements. It also became, in many instances, a path for businesses to rewrite legacy applications using modern programming languages and updates to a technology stack.
Microservices are a collection of small units that continuously deliver and deploy large, complex applications.
What are microservices?
A microservices architecture, also simply known as “microservices”, is an approach to building an application as a series of independently deployable services that are decentralized and autonomously developed. These services are loosely coupled, independently deployable, and easily maintainable. While a monolithic application is built as a single, indivisible unit, microservices break that unit down into a collection of independent units that contribute to the larger whole. Microservices are an integral part of DevOps, since they are the basis for continuous delivery practices that allow teams to adapt quickly to user requirements.
A microservice is a web service that is responsible for one piece of domain logic. Multiple microservices combine to create an application, with each providing a piece of functionality for a domain. Microservices interact with each other using APIs, like REST or gRPC, but don’t have knowledge of the internal workings of the other services. This harmonious interaction between microservices is a microservice architecture.
With a microservices architecture, developers can organize in smaller teams specializing in different services, with different stacks and decoupled deployments. For example, Jira is powered by multiple microservices, each providing specific capabilities, including searching issues, viewing issue details, comments, issue transitions, and more.
Characteristics of microservices
There is no formal definition of a microservices architecture, but there are some common patterns or characteristics that are important to know.
The basic building block of a microservices architecture is a component, which can be a package of software, web service or resource, application, or a module that contains a series of related functions. Or, more simply explained by Martin Fowler: “software components are things that are independently replaceable and upgradeable.”
In a microservices architecture, each component can be developed, deployed, operated, changed, and redeployed without compromising the function of other services or an application’s integrity.
Components are used with other components to deliver a customer experience or business value. The most common are services and libraries but can encapsulate CLI tools, mobile apps, front-end modules, data pipelines, machine learning models, and many other concepts that can be applied within a microservices architecture.
Once individual components are established, they require a substantial amount of logic to communicate with each other through a communication mechanism like RPC, REST over HTTP, or an event-based system. These mechanisms may be synchronous or asynchronous methods and microservices may use a combination of both.
The most important aspect is that each microservice should provide a clear, intuitive contract that describes how a consumer of that service can use it. This is typically done through an API published alongside the service.
You build it, you run it
The DevOps philosophy of “you build it, you run it” emphasized that you cannot change an architecture into microservices without thinking about how teams are structured. DevOps re-aligns incentives across functional roles — development, QA, release engineering, operations — into a single team with a shared goal of building high-quality software. DevOps practices like CI/CD, automated testing, and feature flags accelerate deployment and help maintain system stability and security. Plus, each team can build and deploy microservices that it owns without affecting other teams.
The evolution of the cloud simplified the building, deploying, and operating of microservices. Infrastructure automation techniques like continuous integration, continuous delivery, and automated tests help teams.
Service-oriented architecture vs. microservices
Service-oriented architecture (SOA) and microservices are two types of web service architectures. Like microservices, an SOA comprises reusable, specialized components that work independently of each other. The distinction between the two architecture types is the bureaucratic classification of service types.
An SOA has four basic service types:
- Infrastructure services
These types define the related domain-specific responsibility of the underlying services. Comparatively, microservices only have two service types: functional and infrastructure.
Both architectures share the same set of standards at different layers of an enterprise. The existence of a microservices architecture comes down to the success of an SOA pattern. Hence, a microservices architecture pattern is a subset of SOA. Here, the main focus is on the runtime autonomy of each service.
Benefits of microservices
Since small, independent teams typically build out a service within microservices, it encourages teams to adopt agile practices. Teams are empowered to work independently and move quickly, which shortens development cycle times.
Since microservices are distributed by design and can be deployed in clusters, they enable dynamic horizontal scaling across service boundaries. If a microservice reaches its load capacity, new instances of that service can rapidly be deployed to the accompanying cluster to help relieve pressure.
One of the primary advantages of microservices is frequent and faster release cycles. As a key element of continuous integration and continuous delivery (CI/CD), microservices allow teams to experiment with new features and roll back if something doesn’t work. This makes it easier to update code and accelerates time-to-market for new features.
Microservice architectures don’t necessarily follow a set approach with one toolchain but allow teams the freedom to select the tools they desire.
Focus on quality
The separation of business concerns into independent microservices means that the service team owning that service focuses on the completed quality deliverable.
By separating functionality, microservices reduce the risk of breaking an entire application or code base when releasing updates. It is easy to isolate and fix faults and bugs in individual services. You can deploy changes only for a specific service, without bringing down the entire application, which provides higher reliability.
Challenges of microservices
Microservices and DevOps: Two peas in a pod
Given the increase in complexity and dependencies of microservices, the DevOps practices of deployment, monitoring, and lifecycle automation are seen as integral to microservices architectures. That’s why microservices are often considered the first step to embracing a DevOps culture, which enables:
- Improved scalability
- Faster delivery and deployment
Key technologies and tools for a microservices architecture
Containers, Docker, and Kubernetes
A container is simply the packaging of an application and all its dependencies, which allows it to be deployed easily and consistently. Because containers don’t have the overhead of their own operating system, they are smaller and lighter-weight than traditional virtual machines. They can spin up and down more quickly, making them a perfect match for the smaller services found within microservices architectures.
With the proliferation of services and containers, orchestrating and managing large groups of containers is essential. Docker is a popular containerization platform and runtime that helps developers build, deploy and run containers. However, running and managing containers at scale is a challenge with Docker alone. Kubernetes and other solutions like Docker Swarm, Mesos, HashiCorp Nomad, and more help to address containerization at scale.
Containerization and the deployment of containers is a new pattern of distributed infrastructure. Docker and Kubernetes package a service into a complete container that can be rapidly deployed and discarded. These infrastructure tools are complementary to the microservices architecture. Microservices can be containerized, easily deployed, and managed using a container management system.
Future of microservices
Containerization and the deployment of containers is now a common pattern of distributed infrastructure. Tools like Docker and Kubernetes package up a service into a complete container, which can be rapidly deployed and discarded. These new infrastructure tools are complementary to the microservices architecture, since microservices can be containerized, easily deployed, and managed using a container management system.
The adoption of microservices should be seen as a journey rather than the immediate goal for a team.
It can be helpful to start small in order to understand the technical requirements of a distributed system and scale individual components. Then gradually extract more services as you gain experience and knowledge.
DevOps を開始する最も簡単な方法は、小さなバリュー ストリーム (小規模なサポート アプリケーションやサービスなど) を特定して一部の DevOps プラクティスを試すことです。ソフトウェア開発と同様、組織を新しい働き方へと一気に移行するよりも、少数の関係者のグループで単一のストリームを変換する方がはるかに簡単です。
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