2024-01-02｜雪崩问题、Spring Cloud微服务集成 Sentinel

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<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>

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spring.cloud.sentinel.transport.dashboard=localhost:8080

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<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

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@Bean
@SentinelRestTemplate(
    blockHandler = "handleBlock",
    fallback = "handleFallback",
    fallbackClass = SentinelFallbackBlockHandler.class,
    blockHandlerClass = SentinelFallbackBlockHandler.class)
public RestTemplate restTemplate() {
    return new RestTemplate();
}

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public class SentinelFallbackBlockHandler {
    public static ClientHttpResponse handleBlock(HttpRequest request, byte[] body, ClientHttpRequestExecution execution, BlockException exception) {
        return new SentinelClientHttpResponse();
    }

    public static ClientHttpResponse handleFallback(HttpRequest request, byte[] body, ClientHttpRequestExecution execution, BlockException ex) {
        return new SentinelClientHttpResponse();
    }
}

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@Slf4j
@RequiredArgsConstructor
public class JsonBlockExceptionHandler implements BlockExceptionHandler {

    private final ObjectMapper objectMapper;

    @Override
    public void handle(HttpServletRequest request, HttpServletResponse response, BlockException e) throws Exception {
        log.error("Sentinel fallback , resource is {}", e.getRule().getResource(), e);

        response.setContentType(MediaType.APPLICATION_JSON_VALUE);
        response.setStatus(HttpStatus.TOO_MANY_REQUESTS.value());
        response.getWriter().print(objectMapper.writeValueAsString(Result.error(ResultCode.TOO_MANY_REQUESTS)));
    }
}

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@Slf4j
public class AutoFallbackSentinelInvocationHandler implements InvocationHandler {
    public static final String EQUALS = "equals";
    public static final String HASH_CODE = "hashCode";
    public static final String TO_STRING = "toString";
    private final Target<?> target;
    private final Map<Method, InvocationHandlerFactory.MethodHandler> dispatch;
    private FallbackFactory<?> fallbackFactory;
    private Map<Method, Method> fallbackMethodMap;

    AutoFallbackSentinelInvocationHandler(Target<?> target, Map<Method, InvocationHandlerFactory.MethodHandler> dispatch,
                                          FallbackFactory<?> fallbackFactory) {
        this.target = checkNotNull(target, "target");
        this.dispatch = checkNotNull(dispatch, "dispatch");
        this.fallbackFactory = fallbackFactory;
        this.fallbackMethodMap = toFallbackMethod(dispatch);
    }

    AutoFallbackSentinelInvocationHandler(Target<?> target, Map<Method, InvocationHandlerFactory.MethodHandler> dispatch) {
        this.target = checkNotNull(target, "target");
        this.dispatch = checkNotNull(dispatch, "dispatch");
    }

    @Override
    public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable {
        if (EQUALS.equals(method.getName())) {
            try {
                Object otherHandler = args.length > 0 && args[0] != null ? Proxy.getInvocationHandler(args[0]) : null;
                return equals(otherHandler);
            } catch (IllegalArgumentException e) {
                return false;
            }
        } else if (HASH_CODE.equals(method.getName())) {
            return hashCode();
        } else if (TO_STRING.equals(method.getName())) {
            return toString();
        }

        Object result;
        InvocationHandlerFactory.MethodHandler methodHandler = this.dispatch.get(method);
        // only handle by HardCodedTarget
        if (target instanceof Target.HardCodedTarget) {
            Target.HardCodedTarget<?> hardCodedTarget = (Target.HardCodedTarget) target;
            MethodMetadata methodMetadata = SentinelContractHolder.METADATA_MAP
                .get(hardCodedTarget.type().getName() + Feign.configKey(hardCodedTarget.type(), method));
            // resource default is HttpMethod:protocol://url
            if (methodMetadata == null) {
                result = methodHandler.invoke(args);
            } else {
                String resourceName = methodMetadata.template().method().toUpperCase() + ':' + hardCodedTarget.url()
                    + methodMetadata.template().path();
                Entry entry = null;
                try {
                    ContextUtil.enter(resourceName);
                    entry = SphU.entry(resourceName, EntryType.OUT, 1, args);
                    result = methodHandler.invoke(args);
                } catch (Throwable ex) {
                    // fallback handle
                    if (!BlockException.isBlockException(ex)) {
                        Tracer.trace(ex);
                    }
                    if (fallbackFactory != null) {
                        try {
                            return fallbackMethodMap.get(method).invoke(fallbackFactory.create(ex), args);
                        } catch (IllegalAccessException e) {
                            // shouldn't happen as method is public due to being an
                            // interface
                            throw new AssertionError(e);
                        } catch (InvocationTargetException e) {
                            throw new AssertionError(e.getCause());
                        }
                    } else {
                        // 若是Result类型 并且不包含@FeignRetry 执行自动降级返回
                        FeignRetry feignRetry = AnnotationUtils.findAnnotation(method, FeignRetry.class);
                        if (Result.class == method.getReturnType() && Objects.isNull(feignRetry)) {
                            log.error("服务调用异常", ex);
                            return Result.error(ResultCode.INNER_SERVICE_ERROR, ex.getMessage());
                        } else {
                            throw ex;
                        }
                    }
                } finally {
                    if (entry != null) {
                        entry.exit(1, args);
                    }
                    ContextUtil.exit();
                }
            }
        } else {
            // other target type using default strategy
            result = methodHandler.invoke(args);
        }

        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof SentinelInvocationHandler) {
            AutoFallbackSentinelInvocationHandler other = (AutoFallbackSentinelInvocationHandler) obj;
            return target.equals(other.target);
        }
        return false;
    }

    @Override
    public int hashCode() {
        return target.hashCode();
    }

    @Override
    public String toString() {
        return target.toString();
    }

    static Map<Method, Method> toFallbackMethod(Map<Method, InvocationHandlerFactory.MethodHandler> dispatch) {
        Map<Method, Method> result = new LinkedHashMap<>();
        for (Method method : dispatch.keySet()) {
            method.setAccessible(true);
            result.put(method, method);
        }
        return result;
    }
}

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public final class AutoFallbackSentinelFeign {
    private AutoFallbackSentinelFeign() {
    }

    public static Builder builder() {
        return new Builder();
    }

    public static final class Builder extends Feign.Builder implements ApplicationContextAware {
        private Contract contract = new Contract.Default();
        private ApplicationContext applicationContext;
        private FeignContext feignContext;

        @Override
        public Feign.Builder invocationHandlerFactory(InvocationHandlerFactory invocationHandlerFactory) {
            throw new UnsupportedOperationException();
        }

        @Override
        public Builder contract(Contract contract) {
            this.contract = contract;
            return this;
        }

        @Override
        public Feign build() {
            super.invocationHandlerFactory(new InvocationHandlerFactory() {
                @Override
                public InvocationHandler create(Target target, Map<Method, MethodHandler> dispatch) {
                    // 查找 FeignClient 上的 降级策略
                    FeignClient feignClient = AnnotationUtils.findAnnotation(target.type(), FeignClient.class);
                    Class<?> fallback = feignClient.fallback();
                    Class<?> fallbackFactory = feignClient.fallbackFactory();

                    String beanName = feignClient.contextId();
                    if (!StringUtils.hasText(beanName)) {
                        beanName = feignClient.name();
                    }

                    Object fallbackInstance;
                    FallbackFactory<?> fallbackFactoryInstance;
                    if (void.class != fallback) {
                        fallbackInstance = getFromContext(beanName, "fallback", fallback, target.type());
                        return new AutoFallbackSentinelInvocationHandler(target, dispatch,
                            new FallbackFactory.Default(fallbackInstance));
                    }

                    if (void.class != fallbackFactory) {
                        //针对 hystrix fallbackFactory 特殊处理
                        try {
                            fallbackFactoryInstance = (FallbackFactory<?>) getFromContext(beanName, "fallbackFactory",
                                fallbackFactory, FallbackFactory.class);
                        } catch (Exception e) {
                            return new AutoFallbackSentinelInvocationHandler(target, dispatch);
                        }
                        return new AutoFallbackSentinelInvocationHandler(target, dispatch, fallbackFactoryInstance);
                    }
                    return new AutoFallbackSentinelInvocationHandler(target, dispatch);
                }

                private Object getFromContext(String name, String type, Class<?> fallbackType, Class<?> targetType) {
                    Object fallbackInstance = feignContext.getInstance(name, fallbackType);
                    if (fallbackInstance == null) {
                        throw new IllegalStateException(String
                            .format("No %s instance of type %s found for loadbalance client %s", type, fallbackType, name));
                    }

                    if (!targetType.isAssignableFrom(fallbackType)) {
                        throw new IllegalStateException(String.format(
                            "Incompatible %s instance. Fallback/fallbackFactory of type %s is not assignable to %s for loadbalance client %s",
                            type, fallbackType, targetType, name));
                    }
                    return fallbackInstance;
                }
            });

            super.contract(new SentinelContractHolder(contract));
            return super.build();
        }

        private Object getFieldValue(Object instance, String fieldName) {
            Field field = ReflectionUtils.findField(instance.getClass(), fieldName);
            field.setAccessible(true);
            try {
                return field.get(instance);
            } catch (IllegalAccessException e) {
                // ignore
            }
            return null;
        }

        @Override
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
            this.applicationContext = applicationContext;
            feignContext = this.applicationContext.getBean(FeignContext.class);
        }
    }
}

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@AutoConfiguration
@AutoConfigureBefore(SentinelFeignAutoConfiguration.class)
@ConditionalOnProperty(name = "feign.sentinel.enabled", havingValue = "true")
public class SentinelFeignConfiguration {
    @Bean
    @Scope("prototype")
    @ConditionalOnMissingBean
    public Feign.Builder autoFallbackSentinelFeignBuilder() {
        return AutoFallbackSentinelFeign.builder();
    }

    @Bean
    @ConditionalOnMissingBean
    public BlockExceptionHandler blockExceptionHandler(ObjectMapper objectMapper) {
        return new JsonBlockExceptionHandler(objectMapper);
    }

    @Bean
    @ConditionalOnMissingBean
    public RequestOriginParser requestOriginParser() {
        return new AllowHeaderRequestOriginParser();
    }
}