Converting from Monolith to Microservices
Migrating monolith to microservices starts by first defining your Domains. When transitioning from monolith to microservices, organizing your reusable components and services into a Domain-Driven Design for microservices is key to a successful monolith conversion and implementation of a microservice-based architecture. Because it is so key for migration, it should be your first step in your cloud-native journey. This is often called Domain-Driven Design (DDD).
The good news is that you can start the migration process by looking at your current monolithic application in terms of components and Domains. From that perspective, you can slowly and successfully see what migrating monolith to microservices will look like.
DeployHub supports a Domain microservices catalog that helps you build out your Domains for component sharing and reuse. It facilitates the move from monolithic applications to microservices by helping you visualize your common services and defining a location for publishing and sharing.
Domains are critical when you begin to decompose functions into independently deployable services. They allow you to catalog similar microservices together, making it easier for other developers to find and share them.
How to Convert Monolithic Application to Microservice
Let’s review a simple way of converting monolith to microservices. We will use a simple example to get you pointed in the right direction. Migrating monolith to microservices can be a task.
To start, let’s break it down by visualizing the monolith into components. If we take a simple web store application, you may have a .jar file, the database, the infrastructure components, and environment variable settings. While the .jar file may be your primary focus, you need to start seeing the database, infrastructure, and environment variables as independent components of your overall application. You can build a migration strategy for managing these layers as individual services.
DeployHub does this using Domains. As previously mentioned, domains are the starting point of migrating monolith to microservices. Domains track, catalog, and expose reusable components allowing them to be easily shared, a critical step in the shift to microservices.
Domains are managed using DeployHub’s back-end versioning engine. This is not suggesting that all microservices of the same Domain are installed in the same container. Each microservice remains independent and in its own container.
How DeployHub Converts Monolith to Microservices
DeployHub allows you to convert monolith to microservices by tracking the logical domains so all microservices of a similar type can be more easily cataloged, referenced, and tracked.
Your monolithic Domains may include:
- Infrastructure Components (java runtime, Tomcat, Environment. Variables)
- Database and SQL (.sql)
- The Website Frontend (.jar)
To visualize this, we can use a triangle that shows the lowest to the highest level of dependencies. This is a simple organizational method that can be useful for our more complex service-based architectures.
Monolithic Dependencies
With DeployHub, these Domains are controlled by different User Groups and can contain lower-level Sub-Domains. For example, Operation Teams may control the Infrastructure Domain, DBAs the middle-tier, and developers control the website frontend. As you break down your application into services, you will expand on these Domains. Starting at this monolithic level helps you begin thinking ‘functions’ and prepares you to move to the next step.
Migrate to Microservices with Domains
One of the first steps of migrating monolith to microservices is to take a monolithic application and break it down into smaller parts, or Domains. We then organize these parts in a fashion that will allow reuse.
If we think about the potential microservices for a simple store website, we’ll have:
- the website front-end
- a cart
- credit card processing
- a check-out system
- advertisements and recommendations
- sign-up
- login
- shipping
- taxes.
We can show how to start migrating monolith to microservices and break down our monolith by representing it in a simple triangle. We start by expanding the triangle into specific sections, the most commonly reused at the bottom and team-specific at the top.
Think about what’s most common. Like our monolithic, the lowest level is infrastructure and database. Our microservice-based architecture is followed by credit card processing and login/sign-up.
Above that, we may have the cart and on top of that are the more specific pieces such as the ads and recommendations. At the peak of the triangle is the front end. While this seems like a simple exercise, it allows you to begin to see the patterns in all applications across the organization. The lower-level sections should be reused.
Microservice Domains
This triangle shows how we build up from the most common pieces and represents how we would define Domains. Each section of our triangle becomes a Domain.
Domains and Sharing
Say we have another team writing a store website, Website B. With DeployHub, they find common pieces based on the Domains.
Once you define your Domains, the next step in the migration process is for your developers to begin publishing and deploying microservices under the Domain structure, making it possible for other teams to easily find and reuse the services. When our next team creates a new store, they begin the process of re-use.
Shared Microservices
Between Website A and B, we have accomplished a level of reuse for all the shareable layers from the infrastructure to the cart. This allows us to write the login, sign up, the cart, and the credit card processing once.
DeployHub facilitates this level of design by supporting a highly customizable Domain structure allowing you to convert monolith to microservices by defining your triangle into a catalog. The domains catalog makes it easy to find and share the microservices.
This domain organization ability is key to a successful migration of monolith to microservice implementation and part of DeployHub’s Domain dependency management features.
In Closing: Migrating Monolith to Microservice
DeployHub is a microservice catalog tool that provides this level of tracking, versioning, and reporting to make every microservice application successful and visible for high-frequency updates. Learn more about converting monolith applications to microservices.
Further Reading:
- Microservice Supply Chain
- Microservice Versioning Management
- Domain-Driven Design for Microservices
- Microservice Configuration Management
- Building Microservice Pipelines
- Microservices Continuous Integration
- Microservice Ownership
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