聊聊spring cloud的RetryableFeignLoadBalancer

序

本文主要研究一下spring cloud的RetryableFeignLoadBalancer

RetryableFeignLoadBalancer

spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/ribbon/RetryableFeignLoadBalancer.java

public class RetryableFeignLoadBalancer extends FeignLoadBalancer
        implements ServiceInstanceChooser {

    private final LoadBalancedRetryFactory loadBalancedRetryFactory;

    public RetryableFeignLoadBalancer(ILoadBalancer lb, IClientConfig clientConfig,
            ServerIntrospector serverIntrospector,
            LoadBalancedRetryFactory loadBalancedRetryFactory) {
        super(lb, clientConfig, serverIntrospector);
        this.loadBalancedRetryFactory = loadBalancedRetryFactory;
        this.setRetryHandler(new DefaultLoadBalancerRetryHandler(clientConfig));
    }

    @Override
    public RibbonResponse execute(final RibbonRequest request,
            IClientConfig configOverride) throws IOException {
        final Request.Options options;
        if (configOverride != null) {
            RibbonProperties ribbon = RibbonProperties.from(configOverride);
            options = new Request.Options(ribbon.connectTimeout(this.connectTimeout),
                    ribbon.readTimeout(this.readTimeout));
        }
        else {
            options = new Request.Options(this.connectTimeout, this.readTimeout);
        }
        final LoadBalancedRetryPolicy retryPolicy = this.loadBalancedRetryFactory
                .createRetryPolicy(this.getClientName(), this);
        RetryTemplate retryTemplate = new RetryTemplate();
        BackOffPolicy backOffPolicy = this.loadBalancedRetryFactory
                .createBackOffPolicy(this.getClientName());
        retryTemplate.setBackOffPolicy(
                backOffPolicy == null ? new NoBackOffPolicy() : backOffPolicy);
        RetryListener[] retryListeners = this.loadBalancedRetryFactory
                .createRetryListeners(this.getClientName());
        if (retryListeners != null && retryListeners.length != 0) {
            retryTemplate.setListeners(retryListeners);
        }
        retryTemplate.setRetryPolicy(retryPolicy == null ? new NeverRetryPolicy()
                : new FeignRetryPolicy(request.toHttpRequest(), retryPolicy, this,
                        this.getClientName()));
        return retryTemplate.execute(new RetryCallback() {
            @Override
            public RibbonResponse doWithRetry(RetryContext retryContext)
                    throws IOException {
                Request feignRequest = null;
                // on retries the policy will choose the server and set it in the context
                // extract the server and update the request being made
                if (retryContext instanceof LoadBalancedRetryContext) {
                    ServiceInstance service = ((LoadBalancedRetryContext) retryContext)
                            .getServiceInstance();
                    if (service != null) {
                        feignRequest = ((RibbonRequest) request
                                .replaceUri(reconstructURIWithServer(
                                        new Server(service.getHost(), service.getPort()),
                                        request.getUri()))).toRequest();
                    }
                }
                if (feignRequest == null) {
                    feignRequest = request.toRequest();
                }
                Response response = request.client().execute(feignRequest, options);
                if (retryPolicy != null
                        && retryPolicy.retryableStatusCode(response.status())) {
                    byte[] byteArray = response.body() == null ? new byte[] {}
                            : StreamUtils
                                    .copyToByteArray(response.body().asInputStream());
                    response.close();
                    throw new RibbonResponseStatusCodeException(
                            RetryableFeignLoadBalancer.this.clientName, response,
                            byteArray, request.getUri());
                }
                return new RibbonResponse(request.getUri(), response);
            }
        }, new LoadBalancedRecoveryCallback() {
            @Override
            protected RibbonResponse createResponse(Response response, URI uri) {
                return new RibbonResponse(uri, response);
            }
        });
    }

    @Override
    public RequestSpecificRetryHandler getRequestSpecificRetryHandler(
            FeignLoadBalancer.RibbonRequest request, IClientConfig requestConfig) {
        return new RequestSpecificRetryHandler(false, false, this.getRetryHandler(),
                requestConfig);
    }

    @Override
    public ServiceInstance choose(String serviceId) {
        return new RibbonLoadBalancerClient.RibbonServer(serviceId,
                this.getLoadBalancer().chooseServer(serviceId));
    }

}

• RetryableFeignLoadBalancer继承了FeignLoadBalancer，实现了ServiceInstanceChooser接口
• 其构造器根据clientConfig创建了DefaultLoadBalancerRetryHandler；其choose方法使用的是getLoadBalancer().chooseServer，最后通过RibbonLoadBalancerClient.RibbonServer包装返回
• 其execute方法首先创建了LoadBalancedRetryPolicy，进而创建retryTemplate，最后通过retryTemplate.execute来实现重试功能；其RetryCallback的doWithRetry方法在retryContext是LoadBalancedRetryContext的条件下会切换下一个service实例来进行重试

小结

RetryableFeignLoadBalancer继承了FeignLoadBalancer，对execute方法使用retryTemplate来实现重试，其中在retryContext是LoadBalancedRetryContext的条件下会切换下一个service实例来进行重试

doc

• RetryableFeignLoadBalancer