如何用未准备好的数据库启动Spring-Boot webapp + Spring-Batch？

Question

Following the "twelve-factor app" recommendations all my spring boot applications are able to start without the database, the health endpoint status become healthy only when the database is available. That's good. But my new spring-boot application includes spring-batch and it breaks this feature.

The issue is quite easy to reproduce, reuse this project

Transform it to a web application with postgresql driver, adding :

     <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
     </dependency>
     <dependency>
         <groupId>org.postgresql</groupId>
         <artifactId>postgresql</artifactId>
         <version>42.2.5</version>
     </dependency>

add a application.properties file :

spring.datasource.url=jdbc:postgresql://localhost:5432/exp_sesame
spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.username=ADMIN
spring.datasource.password=ADMIN
spring.batch.initialize-schema=always

Then, if you start this application it will failed.

org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:280) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.Driver.makeConnection(Driver.java:454) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.Driver.connect(Driver.java:256) ~[postgresql-42.2.5.jar:42.2.5]
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:136) ~[HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:369) ~[HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:198) ~[HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:467) [HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:541) [HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:115) [HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112) [HikariCP-3.2.0.jar:na]
    at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:157) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:115) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:78) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:323) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.boot.jdbc.EmbeddedDatabaseConnection.isEmbedded(EmbeddedDatabaseConnection.java:123) [spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.isEmbedded(DataSourceInitializer.java:140) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.isEnabled(DataSourceInitializer.java:132) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.createSchema(DataSourceInitializer.java:98) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker.afterPropertiesSet(DataSourceInitializerInvoker.java:64) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1837) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1774) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:224) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:1115) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveBean(DefaultListableBeanFactory.java:407) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:341) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:335) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerPostProcessor.postProcessAfterInitialization(DataSourceInitializerPostProcessor.java:55) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:429) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1782) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1247) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1167) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:392) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1321) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1160) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1247) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1167) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:849) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at hello.Application.main(Application.java:10) ~[classes/:na]

Spring-Batch and the database have a strong coupling, i understand but it should start without it (lazy init).

Current Workaround

I move the spring-batch beans in a child context which don't start automatically. In the main spring context, i have a scheduler which checks the database health actuator programmatically and create the child context when the database is up.

Does anyone have a feed back on this ?

Thx folks

Answer 1

Excellent point! This is actually not specific to Spring Batch per se as Spring Batch requires a DataSource bean just like any other application would do.

The point is that the DataSource should be "twelve-factor" ready (if this makes sense) and retry getting connections if the database is down or is not started yet.

There is an open issue in Spring Boot about this feature: See issue #4779 . An example using spring-retry can be found here to decorate the datasource with this retry feature.

FTR, I recommend the 12 Fractured Apps article by Kelsey Hightower in which he addressed the same question (See the Eliminate the need to deploy services in a specific order section). The code example is written in golang but the idea is the same.

Hope this helps.