You have applied either the Client-side Service Discovery pattern or the Server-side Service Discovery pattern. Service instances must be registered with the service registry on startup so that they can be discovered and unregistered on shutdown.
How are service instances registered with and unregistered from the service registry?
A 3rd party registrar is responsible for registering and unregistering a service instance with the service registry. When the service instance starts up, the registrar registers the service instance with the service registry. When the service instance shuts downs, the registrar unregisters the service instance from the service registry.
Examples of the 3rd Party Registration pattern include:
The benefits of the 3rd Party Registration pattern include:
There are also some drawbacks:
The 3rd party registrar might only have superficial knowledge of the state of the service instance, e.g. RUNNING or NOT RUNNING and so might not know whether it can handle requests. However, as mentioned above some registrars such as Netflix Prana perform a health check in order to determine the availability of the service instance.
Unless the registrar is part of the infrastructure it’s another component that must be installed, configured and maintained. Also, since it’s a critical system component it needs to be highly available.
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.
Chris offers numerous resources for learning the microservice architecture.
Chris teaches comprehensive workshops and training classes for executives, architectures 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.
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
Cross cutting concerns