How to create custom retry logic for Spring Datasource? - spring-data-jpa

Question

I'm connecting to an Azure SQL database and my next task is to create custom retry logic when a connection has failed. I would like the retry logic to run both on startup (if needed) as well as any time there's a connection failure while the app is running. I did a test where I removed the IP restrictions from my app and that then caused an exception in my application (as excepted). I'd like to handle when that exception is thrown so that I can trigger a job that verifies both the app and the server are configured correctly. I'm looking for a solution where I can handle these exceptions and retry the DB transaction?
DataSource Config
#Bean
#Primary
public DataSource dataSource() {
return DataSourceBuilder
.create()
.username("username")
.password("password")
.url("jdbc:sqlserver://contoso.database.windows.net:1433;database=*********;user=******#*******;password=*****;encrypt=true;trustServerCertificate=false;hostNameInCertificate=*.database.windows.net;loginTimeout=30;")
.driverClassName("com.microsoft.sqlserver.jdbc.SQLServerDriver")
.build();
}
application.properties
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.SQLServerDialect
spring.jpa.show-sql=true
logging.level.org.springframework.web: ERROR
logging.level.org.hibernate: ERROR
spring.datasource.tomcat.max-wait=10000
spring.datasource.tomcat.max-active=1
spring.datasource.tomcat.test-on-borrow=true
spring.jpa.hibernate.ddl-auto=update

Answer 1

The following code may help you create your retry logic for a data source on Spring Boot:
package com.example.demo;
import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.jdbc.datasource.AbstractDataSource;
import org.springframework.retry.annotation.Backoff;
import org.springframework.retry.annotation.EnableRetry;
import org.springframework.retry.annotation.Retryable;
#SpringBootApplication
#EnableRetry
public class DemoApplication {
#Order(Ordered.HIGHEST_PRECEDENCE)
private class RetryableDataSourceBeanPostProcessor implements BeanPostProcessor {
#Override
public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException {
if (bean instanceof DataSource) {
bean = new RetryableDataSource((DataSource)bean);
}
return bean;
}
#Override
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException {
return bean;
}
}
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
#Bean
public BeanPostProcessor dataSouceWrapper() {
return new RetryableDataSourceBeanPostProcessor();
}
}
class RetryableDataSource extends AbstractDataSource {
private DataSource delegate;
public RetryableDataSource(DataSource delegate) {
this.delegate = delegate;
}
#Override
#Retryable(maxAttempts=10, backoff=#Backoff(multiplier=2.3, maxDelay=30000))
public Connection getConnection() throws SQLException {
return delegate.getConnection();
}
#Override
#Retryable(maxAttempts=10, backoff=#Backoff(multiplier=2.3, maxDelay=30000))
public Connection getConnection(String username, String password)
throws SQLException {
return delegate.getConnection(username, password);
}
}

Answer 2

Not sure what you deem custom but, there is an out-of-the-box option with Spring boot and Aspectj by leveraging the pom.xml in the mavern project, as spring-retry depends on Aspectj:
Add the following dependencies in your project pom.xml:
<dependency>
<groupId>org.springframework.retry</groupId>
<artifactId>spring-retry</artifactId>
<version>${version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aspects</artifactId>
<version>${version}</version>
</dependency>
And then add the #EnableRetry annotation to your code:
package com.example.springretry;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.retry.annotation.EnableRetry;
#EnableRetry
#SpringBootApplication
public class SpringRetryApplication {
public static void main(String[] args) {
SpringApplication.run(SpringRetryApplication.class, args);
}
}
The Spring retry module example can be found here: https://howtodoinjava.com/spring-boot2/spring-retry-module/