如何使用未准备好的数据库启动+Spring-批处理？

Question

按照“十二因素应用程序”的建议，我所有的春季引导应用程序都能够在没有数据库的情况下启动，只有当数据库可用时，健康端点状态才会变得健康。那很好。但是我的新的spring引导应用程序包括spring批处理，它破坏了这个特性。

这个问题很容易复制，重用这个项目

使用postgresql驱动程序将其转换为web应用程序，并添加：

     <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>

添加一个application.properties文件：

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

然后，如果启动此应用程序，它将失败。

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-批处理和数据库有很强的耦合性，我理解，但是它应该在没有它的情况下启动(懒惰)。

当前的解决方案

我在不自动启动的子上下文中移动春季批处理bean。在主要的spring上下文中，我有一个调度程序，它以编程方式检查数据库健康执行器，并在数据库运行时创建子上下文。

有人有这方面的反馈吗？

Thx乡亲

Answer 1

很好的点！这实际上并不是特定于Spring本身的，因为Spring需要一个DataSource bean，就像任何其他应用程序所做的那样。

关键是DataSource应该是“十二因子”就绪(如果这有意义的话)，并且在数据库关闭或尚未启动时重新尝试获取连接。

Spring中有一个关于这个特性的未决问题:请参阅第4779期。使用spring-retry的示例可以找到这里来用这个重试特性来修饰数据源。

FTR，我推荐凯尔西·海塔的12例应用程序骨折文章，他在文章中提到了同样的问题(参见Eliminate the need to deploy services in a specific order一节)。代码示例是用golang编写的，但想法是一样的。

希望这能有所帮助。