Spring Boot Graceful Shutdown

This project adds graceful shutdown behavior to Spring Boot.

⚠️ As of Spring Boot 2.3+, use the native support inside Spring Boot to accomplish graceful shutdown: https://docs.spring.io/spring-boot/docs/current/reference/html/web.html#web.graceful-shutdown. Additionally, when deployed on Kubernetes, add a preStop command: https://docs.spring.io/spring-boot/docs/current/reference/html/deployment.html#deployment.cloud.kubernetes.container-lifecycle

Versions

Multiple branches are maintained to support multiple Spring Boot versions. The following tables show the relation between the Spring Boot version and the Spring Boot Graceful Shutdown version.

Spring Boot	Spring Boot Graceful Shutdown	Branch
1.5.x	1.0.x	1.0.x
2.0.x	2.0.x	2.0.x
2.1.x	2.1.x	2.1.x
2.2.x	2.2.x	master

Flow

1. The JVM receives the SIGTERM signal and starts shutting down the Spring container.
2. A Spring EventListener listens for a ContextClosedEvent and is invoked once the shutdown is started.
3. The EventListener updates a Spring Boot HealthIndicator and puts it "out of service".
4. The context shutdown is delayed using a Thread.sleep to allow the load balancer to see the updated HealthIndicator status and stop forwarding requests to this instance.
5. When the Thread.sleep is finished, the Tomcat container is gracefully shutdown. First by pausing the connector, no longer accepting new request. Next, by allowing the Tomcat thread pool a configurable amount of time to finish the active threads.
6. Finally, the Spring context is closed.

Limitations

Currently this project only supports Tomcat as embedded web container for Spring Boot. Undertow and/or Jetty are not yet supported.

Installation

1. Add the following Maven dependency:

<dependency>
    <groupId>com.github.timpeeters</groupId>
    <artifactId>spring-boot-graceful-shutdown</artifactId>
    <version>X.X.X</version>
</dependency>

Configuration

Key	Default value	Description
graceful.shutdown.enabled	false	Indicates whether graceful shutdown is enabled or not.
graceful.shutdown.timeout	60s	The time to wait for active threads to finish before shutting down the Tomcat connector.
graceful.shutdown.wait	30s	The time to return "out of service" on the health page before starting the graceful shutdown.

It is important to specify the time unit, otherwise you end up with milliseconds.

Alternative implementations

We found several alternatives for graceful shutdown behavior in Spring Boot.

• https://github.com/SchweizerischeBundesbahnen/springboot-graceful-shutdown
• https://github.com/corentin59/spring-boot-graceful-shutdown
• https://github.com/gesellix/graceful-shutdown-spring-boot

References

• spring-projects/spring-boot#4657