Shutown Spring when DB is lost

Use case

Our spring-boot-backend (v 2.3.1) using a postgres-database with HikariCP as connection pool.
The application is online and a admin accidentally kills the database.

Expected behavior

Spring notice that the connection to DB was lost. The application will gracefully shutdown.

Actual behavior

Spring is still running. All methods, which needs the db, ending up in exceptions.
To recover a complete good state, we need manually to restart spring.

Notes
We have a lot of async workers and they cannot recover correctly, when the database is going back online.
And docker/kubernetes will notice when the application shutdown and can automatically restart it.

Question

How can I reach the expected behavior?
Sadly I found nothing similar in the web.

With the hints from @Zubair I build a new small solution.
Iam using the Spring-Actuator-package, because they have some ready classes for this use-case.

All what I need was a HealthIndicator-Bean, like this

@Bean
public HealthIndicator dataSourceHealthIndicator(final DataSource dataSource) {
  return new DataSourceHealthIndicator(dataSource, "SELECT 1;");
}

and scheduled watcher (because HikariCP nor the HealthIndicators has any events).

@Scheduled(fixedRate = 10000L)
public void checkDBHealth() {
  final Status status = this.dataSourceHealthIndicator.health().getStatus();
  if (!Status.UP.equals(status)) {
    log.error("DATABASE IS OFFLINE! SHUTTING DOWN!");
    System.exit(1);
  }
}

I hope that will be useful for others.

Edit

I had to change the config of HikariCP. Otherwise the health-checker waiting almost endless for database-connection.

@Bean
public DataSource dataSource() {
  final HikariConfig config = new HikariConfig();
  // default settings with user, password, jdbc, ...
  config.setInitializationFailTimeout(1000);
  config.setConnectionTimeout(1000);
  config.setValidationTimeout(1000);

  return new HikariDataSource(config);
}

</details>



# 答案2
**得分**: 1

如果是 Spring 2.0 版本，您可以从某个监控服务调用关闭执行器。

<details>
<summary>英文:</summary>

If its spring 2.0, you may call the shut-down actuator from some monitoring service.

</details>



# 答案3
**得分**: 1

你可以在属性文件中禁用默认提供的执行器健康指示器，并通过将自定义的 [DatasourceHealthIndicator][1] 注册为 bean 来替换它。

```java
@Bean
public DataSourceHealthIndicator dataSourceHealthIndicator(){
   return new DataSourceHealthIndicator(dataSource, "SELECT 1");
}

@Component
@RequiredArgsConstructor
public class CustomHealth implements HealthIndicator {

   private final DataSourceHealthIndicator healthIndicator;

   @Override
   public Health health() {
      // ...
      return Health.status(healthIndicator.health().getStatus()).build();
   }
}

并且像这样设置你的属性。

application.yaml

management:
   health:
      db:
         enabled: false

application.properties

management.health.db.enabled: false

@Bean
public DataSourceHealthIndicator dataSourceHealthIndicator(){
   return new DataSourceHealthIndicator(dataSource, "SELECT 1");
}

@Component
@RequiredArgsConstructor
public class CustomHealth implements HealthIndicator {

   private final DataSourceHealthIndicator healthIndicator;

   @Override
   public Health health() {
      // ...
      return Health.status(healthIndicator.health().getStatus()).build();
   }
}

management:
   health:
      db:
         enabled: false

management.health.db.enabled: false