Stelligent Bookclub: "Building Microservices" by Sam Newman
At Stelligent, we put a strong focus on education and so I wanted to share some books that have been popular within our team. Today we explore the world of microservices with “Building Microservices” by Sam Newman.
Microservices are an approach to distributed systems that promotes the use of small independent services within a software solution. By adopting microservices, teams can achieve better scaling and gain autonomy, that allows teams to chose their technologies and iterate independently from other teams.
As a result, a change to one part of the system could unintentionally break a different part, which in turn might lead to hard-to-predict outages
Microservices are an alternative to the development of a monolithic codebase in many organizations – a codebase that contains your entire application and where new code piles on at alarming rates. Monoliths become difficult to work with as interdependencies within the code begin to develop.
As a result, a change to one part of the system could unintentionally break a different part, which in turn might lead to hard-to-predict outages. This is where Newman’s argument about the benefits of microservices really comes into play.
- Reasons to split the monolith
- Increase pace of change
- Smaller team structure
- Adopt the proper technology for a problem
- Remove tangled dependencies
- Remove dependency on databases for integration
- Less technical debt
By splitting monoliths at their seams, we can slowly transform a monolithic codebase into a group of microservices. Each service his loosely coupled and highly cohesive, as a result changes within a microservice do not change it’s function to other parts of the system. Each element works in a blackbox where only the inputs and outputs matter. When splitting a monolith, databases pose some of the greatest challenge; as a result, Newman devotes a significant chunk of the text/book to explaining various useful techniques to reduce these dependencies.
Ways to reduce dependencies
- Clear well documented api
- Loose coupling and high cohesion within a microservice
- Enforce standards on how services can interact with each other
Though Newman’s argument for the adoption of microservices is spot-on, his explanation on continuous delivery and scaling micro-services is shallow. For anyone who has a background in CD or has read “Continuous Delivery” these sections do not deliver. For example, he takes the time to talk about machine images at great length but lightly brushes over build pipelines. The issue I ran into with scaling microservices is Newman suggests that ideally each microservice should ideally be put on its own instance where it exists independently of all other services. Though this is a possibility and it would be nice to have this would be highly unlikely to happen in a production environment where cost is a consideration. Though he does talk about using traditional virtualization, Vagrant, linux containers, and Docker to host multiple services on a single host he remains platform agnostic and general. As a result he misses out on the opportunity to talk about services like Amazon ECS, Kubernetes, or Docker Swarm. Combining these technologies with reserved cloud capacity would be a real world example that I feel would have added a lot to this section
Overall Newman’s presentation of microservices is a comprehensive introduction for IT professionals. Some of the concepts covered are basic but there are many nuggets of insight that are worth reading for. If you are looking to get a good idea about how microservices work, pick it up. If you’re looking to advance your microservice patterns or suggest some, feel free to comment below!
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