多平台统一管理软件接口,如何实现多平台统一管理软件接口
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2023-02-16
浅谈Spring Cloud Ribbon的原理
Ribbon是Netflix发布的开源项目,主要功能是提供客户端的软件负载均衡算法,将Netflix的中间层服务连接在一起。Ribbon客户端组件提供一系列完善的配置项如连接超时,重试等。简单的说,就是在配置文件中列出Load Balancer(简称LB)后面所有的机器,Ribbon会自动的帮助你基于某种规则(如简单轮询,随即连接等)去连接这些机器。我们也很容易使用Ribbon实现自定义的负载均衡算法。
说起负载均衡一般都会想到服务端的负载均衡,常用产品包括LBS硬件或云服务、Nginx等,都是耳熟能详的产品。
而Spring Cloud提供了让服务调用端具备负载均衡能力的Ribbon,通过和Eureka的紧密结合,不用在服务集群内再架设负载均衡服务,很大程度简化了服务集群内的架构。
具体也不想多写虚的介绍,反正哪里都能看得到相关的介绍。
直接开撸代码,通过代码来看Ribbon是如何实现的。
配置
详解:
1.RibbonAutoConfiguration配置生成RibbonLoadBalancerClient实例。
代码位置:
spring-cloud-netflix-core-1.3.5.RELEASE.jar
org.springframework.cloud.netflix.ribbon
RibbonAutoConfiguration.class
@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)
public class RibbonAutoConfiguration {
// 略
@Bean
@ConditionalOnMissingBean(LoadBalancerClient.class)
public LoadBalancerClient loadBalancerClient() {
return new RibbonLoadBalancerClient(springClientFactory());
}
// 略
}
先看配置条件项,RibbonAutoConfiguration配置必须在LoadBalancerAutoConfiguration配置前执行,因为在LoadBalancerAutoConfiguration配置中会使用RibbonLoadBalancerClient实例。
RibbonLoadBalancerClient继承自LoadBalancerClient接口,是负载均衡客户端,也是负载均衡策略的调用方。
2.LoadBalancerInterceptorConfig配置生成:
1).负载均衡拦截器LoadBalancerInterceptor实例
包含:
LoadBalancerClient实现类的RibbonLoadBalancerClient实例
负载均衡的请求创建工厂LoadBalancerRequestFactory:实例
2).RestTemplate自定义的RestTemplateCustomizer实例
代码位置:
spring-cloud-commons-1.2.4.RELEASE.jar
org.springframework.cloud.client.loadbalancer
LoadBalancerAutoConfiguration.class
@Configuration
@ConditionalOnClass(RestTemplate.class)
@ConditionalOnBean(LoadBalancerClient.class)
@EnableConfigurationProperties(LoadBalancerRetryProperties.class)
public class LoadBalancerAutoConfiguration {
// 略
@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 new RestTemplateCustomizer() {
@Override
public void customize(RestTemplate restTemplate) {
List
restTemplate.getInterceptors());
list.add(loadBalancerInterceptor);
restTemplate.setInterceptors(list);
}
};
}
}
// 略
}
先看配置条件项:
要求在项目环境中必须要有RestTemplate类。
要求必须要有LoadBalancerClient接口的实现类的实例,也就是上一步生成的RibbonLoadBalancerClient。
3.通过上面一步创建的RestTemplateCustomizer配置所有RestTemplate实例,就是将负载均衡拦截器设置给RestTemplate实例。
@Configuration
@ConditionalOnClass(RestTemplate.class)
@ConditionalOnBean(LoadBalancerClient.class)
@EnableConfigurationProperties(LoadBalancerRetryProperties.class)
public class LoadBalancerAutoConfiguration {
// 略
@Bean
public SmartInitializingSingleton loadBalancedRestTemplateInitializer(
final List
return http://new SmartInitializingSingleton() {
@Override
public void afterSingletonsInstantiated() {
for (RestTemplate restTemplate : LoadBalancerAutoConfiguration.this.restTemplates) {
for (RestTemplateCustomizer customizer : customizers) {
customizer.customize(restTemplate);
}
}
}
};
}
// 略
@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 new RestTemplateCustomizer() {
@Override
public void customize(RestTemplate restTemplate) {
List
restTemplate.getInterceptors());
list.add(loadBalancerInterceptor);
restTemplate.setInterceptors(list);
}
};
}
}
// 略
}
restTemplate.setInterceptors(list)这个地方就是注入负载均衡拦截器的地方LoadBalancerInterceptor。
从这个地方实际上也可以猜出来,RestTemplate可以通过注入的拦截器来构建相应的请求实现负载均衡。
也能看出来可以自定义拦截器实现其他目的。
4.RibbonClientConfiguration配置生成ZoneAwareLoadBalancer实例
代码位置:
spring-cloud-netflix-core-1.3.5.RELEASE.jar
org.springframework.cloud.netflix.ribbon
RibbonClientConfiguration.class
@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({OkHttpRibbonConfiguration.class, RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class})
public class RibbonClientConfiguration {
// 略
@Bean
@ConditionalOnMissingBean
public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
ServerList
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);
}
// 略
}
ZoneAwareLoadBalancer继承自ILoadBalancer接口,该接口有一个方法:
/**
* Choose a server from load balancer.
*
* @param key An object that the load balancer may use to determine which server to return. null if
* the load balancer does not use this parameter.
* @return server chosen
*/
public Server chooseServer(Object key);
ZoneAwareLoadBalancer就是一个具体的负载均衡实现类,也是默认的负载均衡类,通过对chooseServer方法的实现选取某个服务实例。
拦截&请求
1.使用RestTemplate进行Get、Post等各种请求,都是通过doExecute方法实现
代码位置:
spring-web-4.3.12.RELEASE.jar
org.springframework.web.client
RestTemplate.class
public class RestTemplate extends InterceptingHttpAccessor implements RestOperations {
// 略
protected
ResponseExtractor
Assert.notNull(url, "'url' must not be null");
Assert.notNull(method, "'method' must not be null");
ClientHttpResponse response = null;
try {
ClientHttpRequest request = createRequest(url, method);
if (requestCallback != null) {
requestCallback.doWithRequest(request);
}
response = request.execute();
handleResponse(url, method, response);
if (responseExtractor != null) {
return responseExtractor.extractData(response);
}
else {
return 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();
}
}
}
// 略
}
支持的各种http请求方法最终都是调用doExecute方法,该方法内调用创建方法创建请求实例,并执行请求得到响应对象。
2.生成请求实例创建工厂
上一步代码中,调用createRequest方法创建请求实例,这个方法是定义在父类中。
先整理出主要的继承关系:
createRequest方法实际是定义在HttpAccessor抽象类中。
public abstract class HttpAccessor {
private ClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
public void setRequestFactory(ClientHttpRequestFactory requestFactory) {
Assert.notNull(requestFactory, "ClientHttpRequestFactory must not be null");
this.requestFactory = requestFactory;
}
public ClientHttpRequestFactory getRequestFactory() {
return this.requestFactory;
}
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;
}
}
在createRequest方法中调用getRequestFactory方法获得请求实例创建工厂,实际上getRequestFactory并不是当前HttpAccessor类中定义的,而是在子类InterceptingHttpAccessor中定义的。
public abstract class InterceptingHttpAccessor extends HttpAccessor {
private List
public void setInterceptors(List
this.interceptors = interceptors;
}
public List
return interceptors;
}
@Override
public ClientHttpRequestFactory getRequestFactory() {
ClientHttpRequestFactory delegate = super.getRequestFactory();
if (!CollectionUtils.isEmpty(getInterceptors())) {
return new InterceptingClientHttpRequestFactory(delegate, getInterceptors());
}
else {
return delegate;
}
}
}
在这里做了个小动作,首先还是通过HttpAccessor类创建并获得SimpleClientHttpRequestFactory工厂,这个工厂主要就是在没有拦截器的时候创建基本请求实例。
其次,在有拦截器注入的情况下,创建InterceptingClientHttpRequestFactory工厂,该工厂就是创建带拦截器的请求实例,因为注入了负载均衡拦截器,所以这里就从InterceptingClientHttpRequestFactory工厂创建。
3.通过工厂创建请求实例
创建实例就看工厂的createRequest方法。
public class InterceptingClientHttpRequestFactory extends AbstractClientHttpRequestFactoryWrapper {
private final List
public InterceptingClientHttpRequestFactory(ClientHttpRequestFactory requestFactory,
List
super(requestFactory);
this.interceptors = (interceptors != null ? interceptors : Collections.
}
@Override
protected ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod, ClientHttpRequestFactory requestFactory) {
return new InterceptingClientHttpRequest(requestFactory, this.interceptors, uri, httpMethod);
}
}
就是new了个InterceptingClientHttpRequest实例,并且把拦截器、基本请求实例创建工厂注进去。
4.请求实例调用配置阶段注入的负载均衡拦截器的拦截方法intercept
可从第1步看出,创建完请求实例后,通过执行请求实例的execute方法执行请求。
ClientHttpRequest request = createRequest(url, method);
if (requestCallback != null) {
requestCallback.doWithRequest(request);
}
response = request.execute();
实际请求实例是InterceptingClientHttpRequest,execute实际是在它的父类中。
类定义位置:
spring-web-4.3.12.RELEASE.jar
org.springframework.http.client
InterceptingClientHttpRequest.class
看一下它们的继承关系。
在execute方法中实际调用了子类实现的executeInternal方法。
public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
private final HttpHeaders headers = new HttpHeaders();
private boolean executed = false;
@Override
public final HttpHeaders getHeaders() {
return (this.executed ? HttpHeaders.readOnlyHttpHeaders(this.headers) : this.headers);
}
@Override
public final OutputStream getBody() throws IOException {
assertNotExecuted();
return getBodyInternal(this.headers);
}
@Override
public final ClientHttpResponse execute() throws IOException {
assertNotExecuted();
ClientHttpResponse result = executeInternal(this.headers);
this.executed = true;
return result;
}
protected void assertNotExecuted() {
Assert.state(!this.executed, "ClientHttpRequest already executed");
}
protected abstract OutputStream getBodyInternal(HttpHeaders headers) throws IOException;
protected abstract ClientHttpResponse executeInternal(HttpHeaders headers) throws IOException;
}
其实就是InterceptingClientHttpRequest类的executeInternal方法,其中,又调用了一个执行器InterceptingRequestExecution的execute,通关判断如果有拦截器注入进来过,就调用拦截器的intercept方法。
这里的拦截器实际上就是在配置阶段注入进RestTemplate实例的负载均衡拦截器LoadBalancerInterceptor实例,可参考上面配置阶段的第2步。
class InterceptingClientHttpRequest extends AbstractBufferingClientHttpRequest {
// 略
@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
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 {
ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), request.getMethod());
for (Map.Entry
List
for (String value : values) {
delegate.getHeaders().add(entry.getKey(), value);
}
}
if (body.length > 0) {
StreamUtils.copy(body, delegate.getBody());
}
return delegate.execute();
}
}
}
}
5.负载均衡拦截器调用负载均衡客户端
在负载均衡拦截器LoadBalancerInterceptor类的intercept方法中,又调用了负载均衡客户端LoadBalancerClient实现类的execute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();
Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri);
return this.loadBalancer.execute(serviceName, requestFactory.createRequest(request, body, execution));
}
}
在配置阶段的第1步,可以看到实现类是RibbonLoadBalancerClient。
6.负载均衡客户端调用负载均衡策略选取目标服务实例并发起请求
在RibbonLoadBalancerClient的第一个execute方法以及getServer方法中可以看到,实际上是通过ILoadBalancer的负载均衡器实现类作的chooseServer方法选取一个服务,交给接下来的请求对象发起一个请求。
这里的负载均衡实现类默认是ZoneAwareLoadBalancer区域感知负载均衡器实例,其内部通过均衡策略选择一个服务。
ZoneAwareLoadBalancer的创建可以参考配置阶段的第4步。
public class RibbonLoadBalancerClient implements LoadBalancerClient {
@Override
public
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);
}
@Override
public
Server server = null;
if(serviceInstance instanceof RibbonServer) {
server = ((RibbonServer)serviceInstance).getServer();
}
if (server == null) {
throw new IllegalStateException("No instances available for " + serviceId);
}
RibbonLoadBalancerContext context = this.clientFactory
.getLoadBalancerContext(serviceId);
RibbonStatsRecorder statsRecorder = new RibbonStatsRecorder(context, server);
try {
T returnVal = request.apply(serviceInstance);
statsRecorder.recordStats(returnVal);
return returnVal;
}
// catch IOException and rethrow so RestTemplate behaves correctly
catch (IOException ex) {
statsRecorder.recordStats(ex);
throw ex;
}
catch (Exception ex) {
statsRecorder.recordStats(ex);
ReflectionUtils.rethrowRuntimeException(ex);
}
return null;
}
// 略
protected Server getServer(ILoadBalancer loadBalancer) {
if (loadBalancer == null) {
return null;
}
return loadBalancer.chooseServer("default"); // TODO: better handling of key
}
protected ILoadBalancer getLoadBalancer(String serviceId) {
return this.clientFactory.getLoadBalancer(serviceId);
}
public static class RibbonServer implements ServiceInstance {
private final String serviceId;
private final Server server;
private final boolean secure;
private Map
public RibbonServer(String serviceId, Server server) {
this(serviceId, server, false, Collections.
}
public RibbonServer(String serviceId, Server server, boolean secure,
Map
this.serviceId = serviceId;
this.server = server;
this.secure = secure;
this.metadata = metadata;
}
// 略
}
}
代码撸完,总结下。
普通使用RestTemplate请求其他服务时,内部使用的就是常规的http请求实例发送请求。
为RestTemplate增加了@LoanBalanced 注解后,实际上通过配置,为RestTemplate注入负载均衡拦截器,让负载均衡器选择根据其对应的策略选择合适的服务后,再发送请求。
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