聊聊spring cloud的consulRetryInterceptor

序

本文主要研究一下spring cloud的consulRetryInterceptor

consulRetryInterceptor

spring-cloud-consul-core-2.1.2.RELEASE-sources.jar!/org/springframework/cloud/consul/ConsulAutoConfiguration.java

@Configuration
@EnableConfigurationProperties
@ConditionalOnConsulEnabled
public class ConsulAutoConfiguration {
    //......

    @ConditionalOnClass({ Retryable.class, Aspect.class, AopAutoConfiguration.class })
    @Configuration
    @EnableRetry(proxyTargetClass = true)
    @Import(AopAutoConfiguration.class)
    @EnableConfigurationProperties(RetryProperties.class)
    protected static class RetryConfiguration {

        @Bean(name = "consulRetryInterceptor")
        @ConditionalOnMissingBean(name = "consulRetryInterceptor")
        public RetryOperationsInterceptor consulRetryInterceptor(
                RetryProperties properties) {
            return RetryInterceptorBuilder.stateless()
                    .backOffOptions(properties.getInitialInterval(),
                            properties.getMultiplier(), properties.getMaxInterval())
                    .maxAttempts(properties.getMaxAttempts()).build();
        }

    }

    //......
}

• RetryConfiguration注册了consulRetryInterceptor，它基于RetryProperties创建了RetryOperationsInterceptor

RetryProperties

spring-cloud-consul-core-2.1.2.RELEASE-sources.jar!/org/springframework/cloud/consul/RetryProperties.java

@ConfigurationProperties("spring.cloud.consul.retry")
public class RetryProperties {

    /** Initial retry interval in milliseconds. */
    private long initialInterval = 1000;

    /** Multiplier for next interval. */
    private double multiplier = 1.1;

    /** Maximum interval for backoff. */
    private long maxInterval = 2000;

    /** Maximum number of attempts. */
    private int maxAttempts = 6;

    public RetryProperties() {
    }

    public long getInitialInterval() {
        return this.initialInterval;
    }

    public void setInitialInterval(long initialInterval) {
        this.initialInterval = initialInterval;
    }

    public double getMultiplier() {
        return this.multiplier;
    }

    public void setMultiplier(double multiplier) {
        this.multiplier = multiplier;
    }

    public long getMaxInterval() {
        return this.maxInterval;
    }

    public void setMaxInterval(long maxInterval) {
        this.maxInterval = maxInterval;
    }

    public int getMaxAttempts() {
        return this.maxAttempts;
    }

    public void setMaxAttempts(int maxAttempts) {
        this.maxAttempts = maxAttempts;
    }

    @Override
    public String toString() {
        return new ToStringCreator(this).append("initialInterval", this.initialInterval)
                .append("multiplier", this.multiplier)
                .append("maxInterval", this.maxInterval)
                .append("maxAttempts", this.maxAttempts).toString();
    }

}

• RetryProperties定义了initialInterval、multiplier、maxInterval、maxAttempts属性

AopAutoConfiguration

spring-boot-autoconfigure-2.1.6.RELEASE-sources.jar!/org/springframework/boot/autoconfigure/aop/AopAutoConfiguration.java

@Configuration
@ConditionalOnClass({ EnableAspectJAutoProxy.class, Aspect.class, Advice.class, AnnotatedElement.class })
@ConditionalOnProperty(prefix = "spring.aop", name = "auto", havingValue = "true", matchIfMissing = true)
public class AopAutoConfiguration {

    @Configuration
    @EnableAspectJAutoProxy(proxyTargetClass = false)
    @ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false",
            matchIfMissing = false)
    public static class JdkDynamicAutoProxyConfiguration {

    }

    @Configuration
    @EnableAspectJAutoProxy(proxyTargetClass = true)
    @ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true",
            matchIfMissing = true)
    public static class CglibAutoProxyConfiguration {

    }

}

• AopAutoConfiguration根据 spring.aop.proxy-target-class 来注入不同的代理方式，默认是cglib代理

RetryOperationsInterceptor

spring-retry-1.2.4.RELEASE-sources.jar!/org/springframework/retry/interceptor/RetryOperationsInterceptor.java

public class RetryOperationsInterceptor implements MethodInterceptor {

    private RetryOperations retryOperations = new RetryTemplate();

    private MethodInvocationRecoverer<?> recoverer;

    private String label;

    public void setLabel(String label) {
        this.label = label;
    }

    public void setRetryOperations(RetryOperations retryTemplate) {
        Assert.notNull(retryTemplate, "'retryOperations' cannot be null.");
        this.retryOperations = retryTemplate;
    }

    public void setRecoverer(MethodInvocationRecoverer<?> recoverer) {
        this.recoverer = recoverer;
    }

    public Object invoke(final MethodInvocation invocation) throws Throwable {

        String name;
        if (StringUtils.hasText(label)) {
            name = label;
        } else {
            name = invocation.getMethod().toGenericString();
        }
        final String label = name;

        RetryCallback<Object, Throwable> retryCallback = new RetryCallback<Object, Throwable>() {

            public Object doWithRetry(RetryContext context) throws Exception {
                
                context.setAttribute(RetryContext.NAME, label);

                /*
                 * If we don't copy the invocation carefully it won't keep a reference to
                 * the other interceptors in the chain. We don't have a choice here but to
                 * specialise to ReflectiveMethodInvocation (but how often would another
                 * implementation come along?).
                 */
                if (invocation instanceof ProxyMethodInvocation) {
                    try {
                        return ((ProxyMethodInvocation) invocation).invocableClone().proceed();
                    }
                    catch (Exception e) {
                        throw e;
                    }
                    catch (Error e) {
                        throw e;
                    }
                    catch (Throwable e) {
                        throw new IllegalStateException(e);
                    }
                }
                else {
                    throw new IllegalStateException(
                            "MethodInvocation of the wrong type detected - this should not happen with Spring AOP, " +
                                    "so please raise an issue if you see this exception");
                }
            }

        };

        if (recoverer != null) {
            ItemRecovererCallback recoveryCallback = new ItemRecovererCallback(
                    invocation.getArguments(), recoverer);
            return this.retryOperations.execute(retryCallback, recoveryCallback);
        }

        return this.retryOperations.execute(retryCallback);

    }

    /**
     * @author Dave Syer
     *
     */
    private static final class ItemRecovererCallback implements RecoveryCallback<Object> {

        private final Object[] args;

        private final MethodInvocationRecoverer<?> recoverer;

        /**
         * @param args the item that failed.
         */
        private ItemRecovererCallback(Object[] args, MethodInvocationRecoverer<?> recoverer) {
            this.args = Arrays.asList(args).toArray();
            this.recoverer = recoverer;
        }

        public Object recover(RetryContext context) {
            return recoverer.recover(args, context.getLastThrowable());
        }

    }

}

• RetryOperationsInterceptor实现了aopalliance的MethodInterceptor；它将invocation包装为retryCallback，然后使用RetryTemplate实现重试

小结

• RetryConfiguration注册了consulRetryInterceptor，它基于RetryProperties创建了RetryOperationsInterceptor
• RetryProperties定义了initialInterval、multiplier、maxInterval、maxAttempts属性
• RetryOperationsInterceptor实现了aopalliance的MethodInterceptor；它将invocation包装为retryCallback，然后使用RetryTemplate实现重试

doc

• RetryProperties