SpringBoot技术实践-SpringRetry重试框架

冷不防 2022-08-31 09:59 197阅读 0赞

# 一、环境搭建 #

1.  加入SpringRetry依赖，SpringRetry使用AOP实现，所以也需要加入AOP包

<dependency>
    	  <groupId>org.springframework.retry</groupId>
    	  <artifactId>spring-retry</artifactId>
    </dependency>
    <dependency>
    	  <groupId>org.springframework</groupId>
    	  <artifactId>spring-aspects</artifactId>
    </dependency>

1.  官方文档
    
     *  [https://www.baeldung.com/spring-retry][https_www.baeldung.com_spring-retry]

# 二、RetryTemplate #

## 2.1 RetryTemplate ##

1.  RetryTemplate封装了Retry基本操作
    
     *  org.springframework.retry.support.RetryTemplate
2.  RetryTemplate中可以指定监听、回退策略、重试策略等
3.  只需要正常new RetryTemplate()即可使用

## 2.2 RetryListener ##

1.  RetryListener指定了当执行过程中出现错误时的回调
    
     *  org.springframework.retry.RetryListener

package org.springframework.retry;
    
    public interface RetryListener { 
    
    	/** * 任务开始执行时调用，只调用一次 */
    	<T, E extends Throwable> boolean open(RetryContext context, RetryCallback<T, E> callback);
    
    	/** * 任务执行结束时(包含重试)调用，只调用一次 */
    	<T, E extends Throwable> void close(RetryContext context, RetryCallback<T, E> callback, Throwable throwable);
    
    	/** * 出现错误时回调 */
    	<T, E extends Throwable> void onError(RetryContext context, RetryCallback<T, E> callback, Throwable throwable);
    }

1.  配置之后在RetryTemplate中指定

## 2.3 回退策略 ##

### 2.3.1 FixedBackOffPolicy ###

1.  当出现错误时延迟多少时间继续调用

FixedBackOffPolicy fixedBackOffPolicy = new FixedBackOffPolicy();
    fixedBackOffPolicy.setBackOffPeriod(1000L);
    retryTemplate.setBackOffPolicy(fixedBackOffPolicy);

1.  配置之后在RetryTemplate中指定

### 2.3.2 ExponentialBackOffPolicy ###

1.  当出现错误时第一次按照指定延迟时间延迟后按照指数进行延迟

// 指数回退(秒)，第一次回退1s，第二次回退2s，第三次4秒，第四次8秒
    ExponentialBackOffPolicy exponentialBackOffPolicy = new ExponentialBackOffPolicy();
    exponentialBackOffPolicy.setInitialInterval(1000L);
    exponentialBackOffPolicy.setMultiplier(2);
    retryTemplate.setBackOffPolicy(exponentialBackOffPolicy);

1.  配置之后在RetryTemplate中指定

## 2.4 重试策略 ##

1.  重试策略主要指定出现错误时重试次数

// 重试策略
    SimpleRetryPolicy retryPolicy = new SimpleRetryPolicy();
    retryPolicy.setMaxAttempts(5);
    retryTemplate.setRetryPolicy(retryPolicy);

1.  配置之后在RetryTemplate中指定

## 2.5 RetryCallback ##

1.  RetryCallback为retryTemplate.execute时执行的回调
    
     *  public final <T, E extends Throwable> T execute(RetryCallback<T, E> retryCallback) throws E

![image.png][]

## 2.6 核心使用 ##

1.  可以使用RetryTemplate完成简单使用
2.  配置retryTemplate
    
     *  指定回退策略为ExponentialBackOffPolicy
     *  指定重试策略为SimpleRetryPolicy
     *  指定监听器RetryListener

import com.codecoord.util.PrintUtil;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.retry.RetryCallback;
    import org.springframework.retry.RetryContext;
    import org.springframework.retry.RetryListener;
    import org.springframework.retry.backoff.ExponentialBackOffPolicy;
    import org.springframework.retry.policy.SimpleRetryPolicy;
    import org.springframework.retry.support.RetryTemplate;
    
    @Configuration
    public class RetryTemplateConfig { 
    
        /** * 注入retryTemplate */
        @Bean
        public RetryTemplate retryTemplate() { 
            RetryTemplate retryTemplate = new RetryTemplate();
    
            /// 回退固定时间(秒)
           /* FixedBackOffPolicy fixedBackOffPolicy = new FixedBackOffPolicy(); fixedBackOffPolicy.setBackOffPeriod(1000L); retryTemplate.setBackOffPolicy(fixedBackOffPolicy);*/
    
            // 指数回退(秒)，第一次回退1s，第二次回退2s
            ExponentialBackOffPolicy exponentialBackOffPolicy = new ExponentialBackOffPolicy();
            exponentialBackOffPolicy.setInitialInterval(1000L);
            exponentialBackOffPolicy.setMultiplier(2);
            retryTemplate.setBackOffPolicy(exponentialBackOffPolicy);
    
            // 重试策略
            SimpleRetryPolicy retryPolicy = new SimpleRetryPolicy();
            retryPolicy.setMaxAttempts(5);
            retryTemplate.setRetryPolicy(retryPolicy);
    
            // 设置监听器，open和close分别在启动和结束时执行一次
            RetryListener[] listeners = { 
                    new RetryListener() { 
                        @Override
                        public <T, E extends Throwable> boolean open(RetryContext context, RetryCallback<T, E> callback) { 
                            PrintUtil.print("open");
                            return true;
                        }
                        @Override
                        public <T, E extends Throwable> void close(RetryContext context, RetryCallback<T, E> callback,
                                Throwable throwable) { 
                            PrintUtil.print("close");
                        }
                        @Override
                        public <T, E extends Throwable> void onError(RetryContext context, RetryCallback<T, E> callback,
                                Throwable throwable) { 
                            PrintUtil.print("onError");
                        }
                    }
            };
            retryTemplate.setListeners(listeners);
    
            return retryTemplate;
        }
    }

1.  在controller中注入RetryTemplate使用，也可以是在service中

@RestController
    public class SpringRetryController { 
        @Resource
        private RetryTemplate retryTemplate;
        private static int count = 0;
    
        @RequestMapping("/retry")
        public Object retry() { 
            try { 
                count = 0;
                retryTemplate.execute((RetryCallback<Void, RuntimeException>) context -> { 
                    // 业务代码
                    // ....
                    // 模拟抛出异常
                    ++count;
                    throw new RuntimeException("抛出异常");
                });
            } catch (RuntimeException e) { 
                System.out.println("Exception");
            }
    
            return "retry = " + count;
        }
    }

1.  访问retry接口，然后观察日志输出

18:27:20.648 - http-nio-8888-exec-1 - open
    18:27:20.649 - http-nio-8888-exec-1 - retryTemplate.execute执行
    18:27:20.649 - http-nio-8888-exec-1 - onError
    18:27:21.658 - http-nio-8888-exec-1 - retryTemplate.execute执行
    18:27:21.658 - http-nio-8888-exec-1 - onError
    18:27:23.670 - http-nio-8888-exec-1 - retryTemplate.execute执行
    18:27:23.670 - http-nio-8888-exec-1 - onError
    18:27:27.679 - http-nio-8888-exec-1 - retryTemplate.execute执行
    18:27:27.679 - http-nio-8888-exec-1 - onError
    18:27:35.681 - http-nio-8888-exec-1 - retryTemplate.execute执行
    18:27:35.681 - http-nio-8888-exec-1 - onError
    18:27:35.681 - http-nio-8888-exec-1 - close

# 三、EnableRetry #

1.  @EnableRetry开启重试，在类上指定的时候方法将默认执行，重试三次
2.  定义service，开启@EnableRetry注解和指定@Retryable，重试可以参考后面一节

import org.springframework.retry.annotation.Retryable;
    
    public interface RetryService { 
    
        /** * 重试方法调用 */
        @Retryable
        void retryServiceCall();
    }

import org.springframework.retry.annotation.EnableRetry;
    import org.springframework.stereotype.Service;
    
    @EnableRetry
    @Service
    public class RetryServiceImpl implements RetryService { 
    
        @Override
        public void retryServiceCall() { 
            PrintUtil.print("方法调用..");
            throw new RuntimeException("手工异常");
        }
    }

1.  controller中注入service

@RequestMapping("/retryAnnotation")
    public Object retryAnnotation() { 
        retryService.retryServiceCall();
        return "retryAnnotation";
    }

1.  将会默认重试

18:46:48.721 - http-nio-8888-exec-1 - 方法调用..
    18:46:49.724 - http-nio-8888-exec-1 - 方法调用..
    18:46:50.730 - http-nio-8888-exec-1 - 方法调用..
    java.lang.RuntimeException: 手工异常

# 四、Retryable #

1.  用于需要重试的方法上的注解
2.  有以下几个属性
    
     *  Retryable注解参数
        
         *  value：指定发生的异常进行重试
         *  include：和value一样，默认空，当exclude也为空时，所有异常都重试
         *  exclude：指定异常不重试，默认空，当include也为空时，所有异常都重试
         *  maxAttemps：重试次数，默认3
         *  backoff：重试补偿机制，默认没有
     *  @Backoff 注解 重试补偿策略
        
         *  不设置参数时，默认使用FixedBackOffPolicy（指定等待时间），重试等待1000ms
         *  设置delay，使用FixedBackOffPolicy（指定等待设置delay和maxDealy时，重试等待在这两个值之间均态分布）
         *  设置delay、maxDealy、multiplier，使用 ExponentialBackOffPolicy（指数级重试间隔的实现），multiplier即指定延迟倍数，比如delay=5000L，multiplier=2,则第一次重试为5秒，第二次为10秒，第三次为20秒

@Target({  ElementType.METHOD, ElementType.TYPE })
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface Retryable { 
    
    	/** * Retry interceptor bean name to be applied for retryable method. Is mutually * exclusive with other attributes. * @return the retry interceptor bean name */
    	String interceptor() default "";
    
    	/** * 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 { };
    
    	/** * Exception types that are retryable. Defaults to empty (and if excludes is also * empty all exceptions are retried). * @return exception types to retry */
    	Class<? extends Throwable>[] include() default { };
    
    	/** * Exception types that are not retryable. Defaults to empty (and if includes is also * empty all exceptions are retried). * If includes is empty but excludes is not, all not excluded exceptions are retried * @return exception types not to retry */
    	Class<? extends Throwable>[] exclude() default { };
    
    	/** * A unique label for statistics reporting. If not provided the caller may choose to * ignore it, or provide a default. * * @return the label for the statistics */
    	String label() default "";
    
    	/** * Flag to say that the retry is stateful: i.e. exceptions are re-thrown, but the * retry policy is applied with the same policy to subsequent invocations with the * same arguments. If false then retryable exceptions are not re-thrown. * @return true if retry is stateful, default false */
    	boolean stateful() default false;
    
    	/** * @return the maximum number of attempts (including the first failure), defaults to 3 */
    	int maxAttempts() default 3;
    
    	/** * @return an expression evaluated to the maximum number of attempts (including the first failure), defaults to 3 * Overrides {@link #maxAttempts()}. * @date 1.2 */
    	String maxAttemptsExpression() default "";
    
    	/** * Specify the backoff properties for retrying this operation. The default is a * simple {@link Backoff} specification with no properties - see it's documentation * for defaults. * @return a backoff specification */
    	Backoff backoff() default @Backoff();
    
    	/** * Specify an expression to be evaluated after the {@code SimpleRetryPolicy.canRetry()} * returns true - can be used to conditionally suppress the retry. Only invoked after * an exception is thrown. The root object for the evaluation is the last {@code Throwable}. * Other beans in the context can be referenced. * For example: * <pre class=code> * {@code "message.contains('you can retry this')"}. * </pre> * and * <pre class=code> * {@code "@someBean.shouldRetry(#root)"}. * </pre> * @return the expression. * @date 1.2 */
    	String exceptionExpression() default "";
    
    	/** * Bean names of retry listeners to use instead of default ones defined in Spring context * @return retry listeners bean names */
    	String[] listeners() default { };
    
    }

@Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface Backoff { 
    
    	/** * Synonym for {@link #delay()}. * * @return the delay in milliseconds (default 1000) */
    	long value() default 1000;
    
    	/** * 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;
    
    	/** * The maximimum wait (in milliseconds) between retries. If less than the * {@link #delay()} then the default of * {@value org.springframework.retry.backoff.ExponentialBackOffPolicy#DEFAULT_MAX_INTERVAL} * is applied. * * @return the maximum delay between retries (default 0 = ignored) */
    	long maxDelay() default 0;
    
    	/** * If positive, then used as a multiplier for generating the next delay for backoff. * * @return a multiplier to use to calculate the next backoff delay (default 0 = * ignored) */
    	double multiplier() default 0;
    
    	/** * An expression evaluating to the canonical backoff period. Used as an initial value * in the exponential case, and as a minimum value in the uniform case. Overrides * {@link #delay()}. * @return the initial or canonical backoff period in milliseconds. * @date 1.2 */
    	String delayExpression() default "";
    
    	/** * An expression evaluating to the maximimum wait (in milliseconds) between retries. * If less than the {@link #delay()} then the default of * {@value org.springframework.retry.backoff.ExponentialBackOffPolicy#DEFAULT_MAX_INTERVAL} * is applied. Overrides {@link #maxDelay()} * * @return the maximum delay between retries (default 0 = ignored) * @date 1.2 */
    	String maxDelayExpression() default "";
    
    	/** * Evaluates to a vaule used as a multiplier for generating the next delay for * backoff. Overrides {@link #multiplier()}. * * @return a multiplier expression to use to calculate the next backoff delay (default * 0 = ignored) * @date 1.2 */
    	String multiplierExpression() default "";
    
    	/** * In the exponential case ({@link #multiplier()} > 0) set this to true to have the * backoff delays randomized, so that the maximum delay is multiplier times the * previous delay and the distribution is uniform between the two values. * * @return the flag to signal randomization is required (default false) */
    	boolean random() default false;
    
    }

1.  在需要重试的方法上配置对应的重试次数、重试异常的异常类型、设置回退延迟时间、重试策略、方法监听名称

@Component
    public class PlatformClassService { 
        @Retryable(
            // 重试异常的异常类型
            value = { Exception.class},
            // 最大重试次数
            maxAttempts = 5,
            // 设置回退延迟时间
            backoff = @Backoff(delay = 500),
            // 配置回调方法名称
            listeners = "retryListener"
        )
        public void call() { 
            System.out.println("call...");
            throw new RuntimeException("手工异常");
        }
    }

// 初始延迟2秒，然后之后验收1.5倍延迟重试，总重试次数4
    @Retryable(value = { Exception.class}, maxAttempts = 4, backoff = @Backoff(delay = 2000L, multiplier = 1.5))

1.  监听方法，在配置类中进行配置

/** * 注解调用 */
    @Bean
    public RetryListener retryListener() { 
        return new RetryListener() { 
            @Override
            public <T, E extends Throwable> boolean open(RetryContext context, RetryCallback<T, E> callback) { 
                System.out.println("open context = " + context + ", callback = " + callback);
                // 返回true继续执行后续调用
                return true;
            }
    
            @Override
            public <T, E extends Throwable> void close(RetryContext context, RetryCallback<T, E> callback,
                                                       Throwable throwable) { 
                System.out.println("close context = " + context + ", callback = " + callback);
            }
            @Override
            public <T, E extends Throwable> void onError(RetryContext context, RetryCallback<T, E> callback,
                                                         Throwable throwable) { 
                System.out.println("onError context = " + context + ", callback = " + callback);
            }
        };
    }

1.  调用服务

@RestController
    public class SpringRetryController { 
        @Resource
        private PlatformClassService platformClassService;
        
        @RequestMapping("/retryPlatformCall")
        public Object retryPlatformCall() { 
            try { 
                platformClassService.call();
            } catch (Exception e) { 
                return "尝试调用失败";
            }
            return "retryPlatformCall";
        }
    }

1.  调用结果

![image.png][image.png 1]

[https_www.baeldung.com_spring-retry]: https://www.baeldung.com/spring-retry
[image.png]: /images/20220829/7b9520f03a3948078f91506df0d2cef7.png
[image.png 1]: /images/20220829/9e2463c91d6141059ff732187a6d8fe8.png