This project shows how to use Spring Boot health checks to monitor an application deployed to Cloud Foundry or Kubernetes.
A Spring Boot app using spring-boot-starter-actuator dependency
will get an endpoint under /actuator/health for free,
which will return a 200 OK HTTP page when the app is ready to serve
traffic:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>When you add more Spring Boot aware dependencies (such as Spring Data JPA or Spring Data MongoDB), an HealthIndicator implementation is automatically registered for you, checking if this component is ready to be used.
In case you need to customize this resource with your own health check,
all you have to do is to register your own HealthIndicator implementation,
like this:
@Configuration
@RequiredArgsConstructor
class AppConfig {
private final AppStatus status;
@Bean
HealthIndicator healthIndicator() {
return () -> status.isLive() ? Health.up().build() : Health.down().build();
}
}
@Data
@Component
class AppStatus {
private boolean live = true;
}In this example, we use component Health which is initialized from a custom value.
You need a JDK 11+ to build this app:
$ ./mvnw clean packageRun this app with generated JAR file:
$ java -jar target/spring-healthcheck-demo.jarThis app is available at http://localhost:8080:
$ curl http://localhost:8080
Application status: UP
Hit http://localhost:8080/getdown to update application status, and see how the platform reacts to this update.%If you hit http://localhost:8080/actuator/health, you can see the
Spring Boot health check endpoint:
$ curl http://localhost:8080/actuator/health
{"status":"UP"}%Now, if you go to http://localhost:8080/getdown, this endpoint will
set the custom health check status to DOWN:
$ curl http://localhost:8080/getdown
Application status set to DOWN%The Spring Boot health check is now returning the updated status:
$ curl http://localhost:8080/actuator/health
{"status":"DOWN"}%Since we do not run this app under a managed platform, this app will not restart. Let's see what happens if you deploy this app to Cloud Foundry or Kubernetes.
Deploy this app using the given Kubernetes descriptors:
$ kubectl apply -f k8s
namespace/spring-healthcheck-demo created
deployment.apps/app created
service/app-lb createdAs you can see, this app is deployed under the namespace spring-healthcheck-demo:
$ kubectl -n spring-healthcheck-demo get pods
NAME READY STATUS RESTARTS AGE
app-5668646795-6tkwv 0/1 Running 0 11sThis app is not marked as READY until the readiness probe under /actuator/health
returns a 200 OK HTTP response:
$ kubectl -n spring-healthcheck-demo get pods
NAME READY STATUS RESTARTS AGE
app-5668646795-6tkwv 1/1 Running 0 24sHere are definitions for readiness probe and liveness probe:
livenessProbe:
# Liveness probe is used to check if this app is still ready to serve traffic
# (after it is marked as "ready").
httpGet:
port: 8080
path: /actuator/health
initialDelaySeconds: 60
periodSeconds: 2
readinessProbe:
# Readiness probe is used to check if this app is ready to serve traffic.
httpGet:
port: 8080
path: /actuator/health
initialDelaySeconds: 15This app is exposed using a LoadBalancer:
$ kubectl -n spring-healthcheck-demo get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
app-lb LoadBalancer 10.100.200.68 35.205.191.100 80:32151/TCP 3m24sHit the external IP (in this example: 35.205.191.100) to access this app:
$ curl 35.205.191.100
Application status: UP
Hit http://35.205.191.100/getdown to update application status, and see how the platform reacts to this update.%As soon as you hit http://35.205.191.100/getdown, the custom health check will be
updated, and the liveness probe will see the new value:
$ curl http://35.205.191.100/getdown
Application status set to DOWN%This app is marked as not ready:
$ kubectl -n spring-healthcheck-demo get pods
NAME READY STATUS RESTARTS AGE
app-5668646795-6tkwv 0/1 Running 1 5m18sA few seconds later, the pod is restarted:
$ kubectl -n spring-healthcheck-demo get pods
NAME READY STATUS RESTARTS AGE
app-5668646795-6tkwv 1/1 Running 1 6m11s
Deploy this app to Cloud Foundry:
$ cf pushA random route is assigned to this app:
$ cf app spring-healthcheck-demo
Showing health and status for app spring-healthcheck-demo in org EMEA / space aroman as [email protected]...
name: spring-healthcheck-demo
requested state: started
routes: spring-healthcheck-demo-appreciative-numbat.cfapps.io
last uploaded: Fri 26 Apr 17:00:34 CEST 2019
stack: cflinuxfs3
buildpacks: client-certificate-mapper=1.8.0_RELEASE
container-security-provider=1.16.0_RELEASE
java-buildpack=v4.19-offline-https://github.com/cloudfoundry/java-buildpack.git#3f4eee2
java-main java-opts java-security
jvmkill-agent=1.16.0_RELEASE open-jdk-...
type: web
instances: 1/1
memory usage: 1024M
state since cpu memory disk details
#0 running 2019-04-26T15:27:02Z 0.4% 163.7M of 1G 129.2M of 1GHit this random route to access this app:
$ curl http://spring-healthcheck-demo-appreciative-numbat.cfapps.io
Application status: UP
Hit http://spring-healthcheck-demo-appreciative-numbat.cfapps.io/getdown to update application status, and see how the platform reacts to this update.%Health checks are defined in the app manifest:
---
applications:
- name: spring-healthcheck-demo
path: target/spring-healthcheck-demo.jar
random-route: true
# You need to set these entries to tell Cloud Foundry how to monitor this app:
# Spring Boot automatically exposes an HTTP endpoint for you.
health-check-type: http
health-check-http-endpoint: /actuator/healthThat's all you need to set your app health check endpoint. As soon as you update the health check status, this app is automatically restarted by Cloud Foundry.
Contributions are always welcome!
Feel free to open issues & send PR.
Copyright © 2019 Pivotal Software, Inc.
This project is licensed under the Apache Software License version 2.0.
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