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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.

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Chris offers numerous resources for learning the microservice architecture.

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Chris teaches comprehensive workshops and training classes for executives, architectures and developers to help your organization use microservices effectively. Learn how to avoid the pitfalls of adopting microservices and learn essential topics, such as service decomposition and design and Kubernetes.

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Example microservices applications

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Use the Eventuate.io platform to tackle distributed data management challenges in your microservices architecture.

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Assess your application's microservice architecture and identify what needs to be improved.

Consulting services

Engage Chris to conduct an architectural assessment.

Self assessment

Alternatively, conduct a self-assessment using the Microservices Assessment Platform.

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Pattern: Health Check API


You have applied the Microservice architecture pattern. Sometimes a service instance can be incapable of handling requests yet still be running. For example, it might have ran out of database connections. When this occurs, the monitoring system should generate a alert. Also, the load balancer or service registry should not route requests to the failed service instance.


How to detect that a running service instance is unable to handle requests?


  • An alert should be generated when a service instance fails
  • Requests should be routed to working service instances


A service has an health check API endpoint (e.g. HTTP /health) that returns the health of the service. The API endpoint handler performs various checks, such as

  • the status of the connections to the infrastructure services used by the service instance
  • the status of the host, e.g. disk space
  • application specific logic

A health check client - a monitoring service, service registry or load balancer - periodically invokes the endpoint to check the health of the service instance.


The Microservices Example application is an example on an application implements a health check API. It is written in Scala and uses Spring Boot and Spring Cloud as the Microservice chassis. They provide various capabilities including a health check endpoint. The endpoint is implemented by the Spring Boot Actuator module. It configures a /health HTTP endpoint that invokes extensible health check logic.

To enable a /health endpoint, first define actuator as a dependency:

dependencies {
  compile "org.springframework.boot:spring-boot-starter-actuator"

Second, enable Spring Boot autoconfiguration:

class UserRegistrationConfiguration {

At this point, your application will have a health check endpoint with default behavior.

You can customize this behavior by defining one or more Spring beans that implement the HealthIndicator interface:

class UserRegistrationConfiguration {
  def discoveryHealthIndicator(discoveryClient : EurekaClient ) : HealthIndicator = new DiscoveryHealthIndicator(discoveryClient)

A HealthIndicator must implement a health() method, which returns a Health value.

Resulting Context

This pattern has the following benefits:

  • The health check endpoint enables the health of a service instance to be periodically tested

This pattern has the following drawbacks:

  • The health check might not sufficiently comprehensive or the service instance might fail between health checks and so requests might still be routed to a failed service instance

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