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springcloud ribbon @LoadBalance负载均衡源码流程分析

2021-12-13 12:58:55  阅读：197  来源： 互联网

标签：return springcloud LoadBalance springframework class 源码 org public cloud


一、编写示例

   1.服务端

    pom.xml

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Finchley.SR2</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>0.2.1.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    2.提供者代码，就是一个普通的HTTP REST接口。

@SpringBootApplication
@EnableDiscoveryClient
@RestController
@Slf4j
public class ProviderApplication {

    public static void main(String[] args) {
        SpringApplication.run(ProviderApplication.class, args);
    }
    @GetMapping("provider")
    public String provider(){
        log.info("..................................");
        return "hello,provider";
    }
}

3.消费端

POM


    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Finchley.SR2</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.retry</groupId>
                    <artifactId>spring-retry</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
<!--        <dependency>-->
<!--            <groupId>org.springframework.retry</groupId>-->
<!--            <artifactId>spring-retry</artifactId>-->
<!--        </dependency>-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <!--<dependency>-->
            <!--<groupId>org.springframework.retry</groupId>-->
            <!--<artifactId>spring-retry</artifactId>-->
        <!--</dependency>-->

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>0.2.1.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

这里注意，如果不想要RetryTemplate，就去掉Retry的依赖，否则默认会引入的。

消费端代码

@SpringBootApplication
@Slf4j
@EnableDiscoveryClient
@RestController
public class ConsumeApplication {

    @Autowired
    RestTemplate restTemplate;

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate(){
        HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
        clientHttpRequestFactory.setConnectTimeout(5 * 1000);
        clientHttpRequestFactory.setReadTimeout(5 * 1000);
        return new RestTemplate(clientHttpRequestFactory);
    }

    public static void main(String[] args) {
        SpringApplication.run(ConsumeApplication.class, args);
    }
    @GetMapping("test")
    public String getContent(){
        log.info("发起请求");
        return restTemplate.getForObject("http://provider/provider",String.class);
    }

}

二、初始化自动配置代码分析

1.org.springframework.cloud.netflix.ribbon.RibbonAutoConfiguration，这个为RIBBON私有的
LoadBalancerClient,LoadBalancer,IRule对象的初始化。
@Configuration
@ConditionalOnClass({ IClient.class, RestTemplate.class, AsyncRestTemplate.class, Ribbon.class})
@RibbonClients
@AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
@AutoConfigureBefore({LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class})
@EnableConfigurationProperties({RibbonEagerLoadProperties.class, ServerIntrospectorProperties.class})
public class RibbonAutoConfiguration {
	@Bean
	public SpringClientFactory springClientFactory() {
		SpringClientFactory factory = new SpringClientFactory();
		factory.setConfigurations(this.configurations);
		return factory;
	}

	@Bean
	@ConditionalOnMissingBean(LoadBalancerClient.class)
	public LoadBalancerClient loadBalancerClient() {
		return new RibbonLoadBalancerClient(springClientFactory());
	}

	@Bean
	@ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
	@ConditionalOnMissingBean
	public LoadBalancedRetryFactory loadBalancedRetryPolicyFactory(final SpringClientFactory clientFactory) {
		return new RibbonLoadBalancedRetryFactory(clientFactory);
	}

2.org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration为springcloud-common的对象自动初始化。 

@Configuration
@ConditionalOnClass(RestTemplate.class)
@ConditionalOnBean(LoadBalancerClient.class)
@EnableConfigurationProperties(LoadBalancerRetryProperties.class)
public class LoadBalancerAutoConfiguration {

	@LoadBalanced
	@Autowired(required = false)
	private List<RestTemplate> restTemplates = Collections.emptyList();

	@Bean
	public SmartInitializingSingleton loadBalancedRestTemplateInitializerDeprecated(
			final ObjectProvider<List<RestTemplateCustomizer>> restTemplateCustomizers) {
		return () -> restTemplateCustomizers.ifAvailable(customizers -> {
            for (RestTemplate restTemplate : LoadBalancerAutoConfiguration.this.restTemplates) {
                for (RestTemplateCustomizer customizer : customizers) {
                    customizer.customize(restTemplate);
                }
            }
        });
	}

	@Autowired(required = false)
	private List<LoadBalancerRequestTransformer> transformers = Collections.emptyList();

	@Bean
	@ConditionalOnMissingBean
	public LoadBalancerRequestFactory loadBalancerRequestFactory(
			LoadBalancerClient loadBalancerClient) {
		return new LoadBalancerRequestFactory(loadBalancerClient, transformers);
	}

	@Configuration
	@ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
	static class LoadBalancerInterceptorConfig {
		@Bean
		public LoadBalancerInterceptor ribbonInterceptor(
				LoadBalancerClient loadBalancerClient,
				LoadBalancerRequestFactory requestFactory) {
			return new LoadBalancerInterceptor(loadBalancerClient, requestFactory);
		}

		@Bean
		@ConditionalOnMissingBean
		public RestTemplateCustomizer restTemplateCustomizer(
				final LoadBalancerInterceptor loadBalancerInterceptor) {
			return restTemplate -> {
                List<ClientHttpRequestInterceptor> list = new ArrayList<>(
                        restTemplate.getInterceptors());
                list.add(loadBalancerInterceptor);
                restTemplate.setInterceptors(list);
            };
		}
	}

 这里的 restTemplate只会取加了@LoadBalance注解的，因为@LoadBalance加上了@Qualifer，这个注解会有筛选过滤作用。

去除了RetryTemplate就会走默认，否则走重试balance.

1.首先创建LoadBalancerRequestFactory工厂对象。

 2.创建LoadBalancerInterceptor对象

3.对RestTemplate列表对象，设置拦截器属性。

 

三、调用分析

  1.RestTemplate.getObject方法开始。这个方法会调用doExecute

public class RestTemplate extends InterceptingHttpAccessor implements RestOperations {	
    @Nullable
	protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback,
			@Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {

		Assert.notNull(url, "URI is required");
		Assert.notNull(method, "HttpMethod is required");
		ClientHttpResponse response = null;
		try {
			ClientHttpRequest request = createRequest(url, method);
			if (requestCallback != null) {
				requestCallback.doWithRequest(request);
			}
			response = request.execute();
			handleResponse(url, method, response);
			return (responseExtractor != null ? responseExtractor.extractData(response) : null);
		}
		catch (IOException ex) {
			String resource = url.toString();
			String query = url.getRawQuery();
			resource = (query != null ? resource.substring(0, resource.indexOf('?')) : resource);
			throw new ResourceAccessException("I/O error on " + method.name() +
					" request for \"" + resource + "\": " + ex.getMessage(), ex);
		}
		finally {
			if (response != null) {
				response.close();
			}
		}
	}

 

2.createRequest方法，RestTemplate是继承于InterceptingHttpAccessor和HttpAccessor

 

	HttpAccessor
protected ClientHttpRequest createRequest(URI url, HttpMethod method) throws IOException {
		ClientHttpRequest request = getRequestFactory().createRequest(url, method);
		if (logger.isDebugEnabled()) {
			logger.debug("Created " + method.name() + " request for \"" + url + "\"");
		}
		return request;
	}

 3.getRequestFactory方法又是来源于InterceptingHttpAccessor，这里会对原有httpRequestFactory工厂包装。

public ClientHttpRequestFactory getRequestFactory() {
		List<ClientHttpRequestInterceptor> interceptors = getInterceptors();
		if (!CollectionUtils.isEmpty(interceptors)) {
			ClientHttpRequestFactory factory = this.interceptingRequestFactory;
			if (factory == null) {
				factory = new InterceptingClientHttpRequestFactory(super.getRequestFactory(), interceptors);
				this.interceptingRequestFactory = factory;
			}
			return factory;
		}
		else {
			return super.getRequestFactory();
		}
	}

public class InterceptingClientHttpRequestFactory extends AbstractClientHttpRequestFactoryWrapper {

	private final List<ClientHttpRequestInterceptor> interceptors;


	/**
	 * Create a new instance of the {@code InterceptingClientHttpRequestFactory} with the given parameters.
	 * @param requestFactory the request factory to wrap
	 * @param interceptors the interceptors that are to be applied (can be {@code null})
	 */
	public InterceptingClientHttpRequestFactory(ClientHttpRequestFactory requestFactory,
			@Nullable List<ClientHttpRequestInterceptor> interceptors) {

		super(requestFactory);
		this.interceptors = (interceptors != null ? interceptors : Collections.emptyList());
	}


	@Override
	protected ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod, ClientHttpRequestFactory requestFactory) {
		return new InterceptingClientHttpRequest(requestFactory, this.interceptors, uri, httpMethod);
	}

}

 所以最后的ClientHttpRequest为InterceptingClientHttpRequest

 3.接着我们回到第一步，response = request.execute();因为已经创建好request，现在开始执行。

class InterceptingClientHttpRequest extends AbstractBufferingClientHttpRequest {

	private final ClientHttpRequestFactory requestFactory;

	private final List<ClientHttpRequestInterceptor> interceptors;

	private HttpMethod method;

	private URI uri;


	protected InterceptingClientHttpRequest(ClientHttpRequestFactory requestFactory,
			List<ClientHttpRequestInterceptor> interceptors, URI uri, HttpMethod method) {

		this.requestFactory = requestFactory;
		this.interceptors = interceptors;
		this.method = method;
		this.uri = uri;
	}


	@Override
	public HttpMethod getMethod() {
		return this.method;
	}

	@Override
	public String getMethodValue() {
		return this.method.name();
	}

	@Override
	public URI getURI() {
		return this.uri;
	}

	@Override
	protected final ClientHttpResponse executeInternal(HttpHeaders headers, byte[] bufferedOutput) throws IOException {
		InterceptingRequestExecution requestExecution = new InterceptingRequestExecution();
		return requestExecution.execute(this, bufferedOutput);
	}


	private class InterceptingRequestExecution implements ClientHttpRequestExecution {

		private final Iterator<ClientHttpRequestInterceptor> iterator;

		public InterceptingRequestExecution() {
			this.iterator = interceptors.iterator();
		}

		@Override
		public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOException {
			if (this.iterator.hasNext()) {
				ClientHttpRequestInterceptor nextInterceptor = this.iterator.next();
				return nextInterceptor.intercept(request, body, this);
			}
			else {
				HttpMethod method = request.getMethod();
				Assert.state(method != null, "No standard HTTP method");
				ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), method);
				request.getHeaders().forEach((key, value) -> delegate.getHeaders().addAll(key, value));
				if (body.length > 0) {
					if (delegate instanceof StreamingHttpOutputMessage) {
						StreamingHttpOutputMessage streamingOutputMessage = (StreamingHttpOutputMessage) delegate;
						streamingOutputMessage.setBody(outputStream -> StreamUtils.copy(body, outputStream));
					}
					else {
						StreamUtils.copy(body, delegate.getBody());
					}
				}
				return delegate.execute();
			}
		}
	}

}

 InterceptingClientHttpRequest的execute会执行executeInternel方法，最后调用

InterceptingRequestExecution.execute

 InterceptingRequestExecution.execute这个方法先会调用各种拦截器进行处理，处理完后，再会由拦截器重新调用这个对象的execute方法，做成责任链模式。最后调用缺省的HTTP代理请求工厂生成代理对象真正发起HTTP请求。

目前的拦截器就是从注册中心获取实例地址，替换URL.

4.接着进行LoadBalancerInterceptor.interropt方法。

public class LoadBalancerInterceptor implements ClientHttpRequestInterceptor {

	private LoadBalancerClient loadBalancer;
	private LoadBalancerRequestFactory requestFactory;

	public LoadBalancerInterceptor(LoadBalancerClient loadBalancer, LoadBalancerRequestFactory requestFactory) {
		this.loadBalancer = loadBalancer;
		this.requestFactory = requestFactory;
	}

	public LoadBalancerInterceptor(LoadBalancerClient loadBalancer) {
		// for backwards compatibility
		this(loadBalancer, new LoadBalancerRequestFactory(loadBalancer));
	}

	@Override
	public ClientHttpResponse intercept(final HttpRequest request, final byte[] body,
			final ClientHttpRequestExecution execution) throws IOException {
		final URI originalUri = request.getURI();
		String serviceName = originalUri.getHost();
		return this.loadBalancer.execute(serviceName, requestFactory.createRequest(request, body, execution));
	}
}

 5.这里的loadBalancer就是RibbonLoadBalancerClient，所以调用这个进行URL替换。

public class RibbonLoadBalancerClient implements LoadBalancerClient {

	private SpringClientFactory clientFactory;

	public RibbonLoadBalancerClient(SpringClientFactory clientFactory) {
		this.clientFactory = clientFactory;
	}

	@Override
	public URI reconstructURI(ServiceInstance instance, URI original) {
		Assert.notNull(instance, "instance can not be null");
		String serviceId = instance.getServiceId();
		RibbonLoadBalancerContext context = this.clientFactory
				.getLoadBalancerContext(serviceId);

		URI uri;
		Server server;
		if (instance instanceof RibbonServer) {
			RibbonServer ribbonServer = (RibbonServer) instance;
			server = ribbonServer.getServer();
			uri = updateToSecureConnectionIfNeeded(original, ribbonServer);
		} else {
			server = new Server(instance.getScheme(), instance.getHost(), instance.getPort());
			IClientConfig clientConfig = clientFactory.getClientConfig(serviceId);
			ServerIntrospector serverIntrospector = serverIntrospector(serviceId);
			uri = updateToSecureConnectionIfNeeded(original, clientConfig,
					serverIntrospector, server);
		}
		return context.reconstructURIWithServer(server, uri);
	}

	@Override
	public ServiceInstance choose(String serviceId) {
		Server server = getServer(serviceId);
		if (server == null) {
			return null;
		}
		return new RibbonServer(serviceId, server, isSecure(server, serviceId),
				serverIntrospector(serviceId).getMetadata(server));
	}

	@Override
	public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
		ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
		Server server = getServer(loadBalancer);
		if (server == null) {
			throw new IllegalStateException("No instances available for " + serviceId);
		}
		RibbonServer ribbonServer = new RibbonServer(serviceId, server, isSecure(server,
				serviceId), serverIntrospector(serviceId).getMetadata(server));

		return execute(serviceId, ribbonServer, request);
	}

6.接着调用RibbonLoadBalancerClient.getLoadBalancer获取负载均衡器。

 7.SpringClientFactory.getLoadBalancer

return getInstance(name, ILoadBalancer.class);这个会去容器工厂自动创建获取ILoadBalancer类。

 8.ribbonLoadBalancingHttpClient为实现类。

	package org.springframework.cloud.netflix.ribbon.apache;


/**
 * @author Spencer Gibb
 */
@Configuration
@ConditionalOnClass(name = "org.apache.http.client.HttpClient")
@ConditionalOnProperty(name = "ribbon.httpclient.enabled", matchIfMissing = true)
public class HttpClientRibbonConfiguration {
@Bean
	@ConditionalOnMissingBean(AbstractLoadBalancerAwareClient.class)
	@ConditionalOnMissingClass(value = "org.springframework.retry.support.RetryTemplate")
	public RibbonLoadBalancingHttpClient ribbonLoadBalancingHttpClient(
		IClientConfig config, ServerIntrospector serverIntrospector,
		ILoadBalancer loadBalancer, RetryHandler retryHandler, CloseableHttpClient httpClient) {
		RibbonLoadBalancingHttpClient client = new RibbonLoadBalancingHttpClient(httpClient, config, serverIntrospector);
		client.setLoadBalancer(loadBalancer);
		client.setRetryHandler(retryHandler);
		Monitors.registerObject("Client_" + this.name, client);
		return client;
	}

9.这个依赖于ribbonLoadBalancer，实际为这个类ZoneAwareLoadBalancer

 

package org.springframework.cloud.netflix.ribbon;


/**
 * @author Dave Syer
 * @author Tim Ysewyn
 */
@SuppressWarnings("deprecation")
@Configuration
@EnableConfigurationProperties
//Order is important here, last should be the default, first should be optional
// see https://github.com/spring-cloud/spring-cloud-netflix/issues/2086#issuecomment-316281653
@Import({HttpClientConfiguration.class, OkHttpRibbonConfiguration.class, RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class})
public class RibbonClientConfiguration {	
@Bean
	@ConditionalOnMissingBean
	public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
			ServerList<Server> serverList, ServerListFilter<Server> serverListFilter,
			IRule rule, IPing ping, ServerListUpdater serverListUpdater) {
		if (this.propertiesFactory.isSet(ILoadBalancer.class, name)) {
			return this.propertiesFactory.get(ILoadBalancer.class, config, name);
		}
		return new ZoneAwareLoadBalancer<>(config, rule, ping, serverList,
				serverListFilter, serverListUpdater);
	}

 10.上面那个类又依赖于IRULE，所以最后创建 ribbonRule，实现类为

ZoneAvoidanceRule

 

 11.创建完RULE后，创建loadBalance

12.创建ribbonLoadBalancer

 13.我们再回到第5步，    @Override
    public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
        ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
        Server server = getServer(loadBalancer);，开始获取server

 

 

 

 14.选择好server后开始执行。

 

 15.回到LoadBalancerRequestFactory.apply

 16.又回到InterceptingRequestExecution.execute

 17.接下来开始替换URL

 18。RibbonLoadBalancerClient.reconstructURI

 

 19.

LoadBalancerContext.reconstructURIWithServer

 20.url替换完毕，调用默认的HTTP代理对象发起请求，返回

 

 

21 请求结束，处理消息体转换，返回数据。 

21.请求完毕。

标签：return,springcloud,LoadBalance,springframework,class,源码,org,public,cloud
来源： https://blog.csdn.net/lipengyao2010/article/details/121902106

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