Let’s imagine you are building an online store that uses the Microservice architecture pattern and that you are implementing the product details page. You need to develop multiple versions of the product details user interface:
In addition, the online store must expose product details via a REST API for use by 3rd party applications.
A product details UI can display a lot of information about a product. For example, the Amazon.com details page for POJOs in Action displays:
Since the online store uses the Microservice architecture pattern the product details data is spread over multiple services. For example,
Consequently, the code that displays the product details needs to fetch information from all of these services.
How do the clients of a Microservices-based application access the individual services?
The granularity of APIs provided by microservices is often different than what a client needs. Microservices typically provide fine-grained APIs, which means that clients need to interact with multiple services. For example, as described above, a client needing the details for a product needs to fetch data from numerous services.
Different clients need different data. For example, the desktop browser version of a product details page desktop is typically more elaborate then the mobile version.
Network performance is different for different types of clients. For example, a mobile network is typically much slower and has much higher latency than a non-mobile network. And, of course, any WAN is much slower than a LAN. This means that a native mobile client uses a network that has very difference performance characteristics than a LAN used by a server-side web application. The server-side web application can make multiple requests to backend services without impacting the user experience where as a mobile client can only make a few.
The number of service instances and their locations (host+port) changes dynamically
Partitioning into services can change over time and should be hidden from clients
Services might use a diverse set of protocols, some of which might not be web friendly
Implement an API gateway that is the single entry point for all clients. The API gateway handles requests in one of two ways. Some requests are simply proxied/routed to the appropriate service. It handles other requests by fanning out to multiple services.
Rather than provide a one-size-fits-all style API, the API gateway can expose a different API for each client. For example, the Netflix API gateway runs client-specific adapter code that provides each client with an API that’s best suited to its requirements.
The API gateway might also implement security, e.g. verify that the client is authorized to perform the request
A variation of this pattern is the Backends for frontends pattern. It defines a separate API gateway for each kind of client.
In this example, there are three kinds of clients: web application, mobile application, and external 3rd party application. There are three different API gateways. Each one is provides an API for its client.
Using an API gateway has the following benefits:
The API gateway pattern has some drawbacks:
Issues:
See the API Gateway that part of my Microservices pattern’s example application. It’s implemented using Spring Cloud Gateway.
Microservices.io is brought to you by Chris Richardson. Experienced software architect, author of POJOs in Action, the creator of the original CloudFoundry.com, and the author of Microservices patterns.
Chris helps clients around the world adopt the microservice architecture through consulting engagements, and training workshops.
Chris teaches comprehensive workshops for architects and developers that will enable your organization use microservices effectively.
Avoid the pitfalls of adopting microservices and learn essential topics, such as service decomposition and design and how to refactor a monolith to microservices.
Learn moreChris offers numerous other resources for learning the microservice architecture.
Want to see an example? Check out Chris Richardson's example applications. See code
Got a specific microservice architecture-related question? For example:
Consider signing up for a two hour, highly focussed, consulting session.
My virtual bootcamp, distributed data patterns in a microservice architecture, is now open for enrollment!
It covers the key distributed data management patterns including Saga, API Composition, and CQRS.
It consists of video lectures, code labs, and a weekly ask-me-anything video conference repeated in multiple timezones.
The regular price is $395/person but use coupon RESVJCMC to sign up for $95 (valid until September 26th, 2023). There are deeper discounts for buying multiple seats.
Take a look at my Manning LiveProject that teaches you how to develop a service template and microservice chassis.
Engage Chris to create a microservices adoption roadmap and help you define your microservice architecture,
Use the Eventuate.io platform to tackle distributed data management challenges in your microservices architecture.
Eventuate is Chris's latest startup. It makes it easy to use the Saga pattern to manage transactions and the CQRS pattern to implement queries.
Engage Chris to conduct an architectural assessment.
Note: tagging is work-in-process
Microservices adoption · ancient lore · anti-patterns · application api · application architecture · architecting · architecture · architecture documentation · assemblage · beer · containers · dark energy and dark matter · deployment · design-time coupling · developer experience · development · devops · docker · eventuate platform · glossary · hexagonal architecture · implementing commands · implementing queries · inter-service communication · kubernetes · loose coupling · microservice architecture · microservice chassis · microservices adoption · microservicesio updates · modular monolith · multi-architecture docker images · observability · pattern · refactoring to microservices · resilience · sagas · security · service api · service architecture · service collaboration · service design · service discovery · service granularity · service template · software delivery metrics · success triangle · tacos · team topologies · transaction management · transactional messaging
Application architecture patterns
Decomposition
Refactoring to microservicesnew
Data management
Transactional messaging
Testing
Deployment patterns
Cross cutting concerns
Communication style
External API
Service discovery
Reliability
Security
Observability
UI patterns