You have applied the Database per Service pattern. Each service has its own database. Some business transactions, however, span multiple service so you need a mechanism to ensure data consistency across services. For example, lets imagine that you are building an e-commerce store where customers have a credit limit. The application must ensure that a new order will not exceed the customer’s credit limit. Since Orders and Customers are in different databases the application cannot simply use a local ACID transaction.
How to maintain data consistency across services?
Use an event-driven, eventually consistent approach. Each service publishes an event whenever it update its data. Other service subscribe to events. When an event is received, a service updates its data.
An e-commerce application that uses this approach would work as follows:
Order Servicecreates an Order in a pending state and publishes an
Customer Servicereceives the event and attempts to reserve credit for that Order. It then publishes either a
Credit Reservedevent or a
Order Servicereceives the event from the
Customer Serviceand changes the state of the order to either approved or cancelled
This pattern has the following benefits:
This solution has the following drawbacks:
There are also the following issues to address:
The article Event-Driven Data Management for Microservices by @crichardson describes this pattern
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 classes and workshops.
In June, I’ll be teaching a public microservices workshopover Zoom in an APAC-friendly (GMT+9) timezone.
Take a look at my Manning LiveProject that teaches you how to develop a service template and microservice chassis.
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 NDULYCPO to sign up for $195 (valid until July 5th, 2022). There are deeper discounts for buying multiple seats.
Chris offers numerous resources for learning the microservice architecture.
Chris teaches comprehensive workshops, training classes and bootcamps for executives, architects and developers to help 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.
Delivered in-person and remotely.
Want to see an example? Check out Chris Richardson's example applications. See code
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.
Join the microservices google group
Application architecture patterns
Refactoring to microservicesnew
Cross cutting concerns