Development scenario
When we interface with other third parties, it is normal to succeed or fail once, but occasionally we encounter third-party network exceptions or response exceptions. Or when you call someone else's interface callback. It may take multiple attempts to get the response.
SpringBoot implements retry mechanism
- Introduce the pom.xml corresponding to the response jar Maven
<dependency>
<groupId>org.springframework.retry</groupId>
<artifactId>spring-retry</artifactId>
</dependency>
- Annotate the startup class @EnableRetry
@SpringBootApplication(exclude = SecurityAutoConfiguration.class)
@EnableRetry
public class App {
@Bean
public RestTemplate restTemplate(){
return new RestTemplate();
}
public static void main(String[] args) {
System.out.println("hello start");
SpringApplication.run(App.class, args);
System.err.println("hello end");
}
}
- Annotate the configuration on the Servcie method that needs to be retried
@Service
public class RetryServiceImpl implements RetryService {
public int count = 0;
public long t = 0;
@Override
@Retryable(value = RetryException.class, maxAttempts = 3, backoff = @Backoff(delay = 1000 * 2, multiplier = 1.5))
public void TestRetryMethod(String name) {
// TODO Auto-generated method stub
count++;
Long s = System.currentTimeMillis();
t = s;
if(name == null) {
System.err.println("第"+count+"次尝试"+System.currentTimeMillis());
throw new RetryException("retry");
}
}
}
Retryable annotation analysis value
/**
* Exception types that are retryable. Synonym for includes(). Defaults to empty (and
* if excludes is also empty all exceptions are retried).
* @return exception types to retry
*/
Class<? extends Throwable>[] value() default {};
Through the English comments, you can know that the retry mechanism will only be used when the exception is thrown.
Retryable annotation analysis maxAttempts
/**
* @return the maximum number of attempts (including the first failure), defaults to 3
*/
int maxAttempts() default 3;
The maximum number of attempts is not configured and the default is 3 times.
backoff annotation analysis delay
/**
* A canonical backoff period. Used as an initial value in the exponential case, and
* as a minimum value in the uniform case.
* @return the initial or canonical backoff period in milliseconds (default 1000)
*/
long delay() default 0;
Try again after how many milliseconds.
backoff annotation analysis multiplier
This is a multiple of the time interval. For example, if you configure a delay of 1000 and a multiplier of 2, it means that the first attempt is 1 second, the second is 2 seconds, the third is 4 seconds, and so on.
Summary: The underlying principle is the idea of aop.
test
