1 描述

如果我们直接使用SpringCloud Feign进行服务间调用的时候，http组件使用的是JDK的HttpURLConnection，每次请求都会新建一个连接，没有使用线程池复用。具体的可以从源码进行分析

2 源码分析

我们在分析源码很难找到入口，不知道从何开始入手，我们在分析SpringCloud feign的时候可用在配置文件下面我讲一下个人的思路。

1 首先我点击@EnableFeignClients 看一下这个注解在哪个资源路径下
如下图所示：
2 找到服务启动加载的配置文件
3 因为feign底层的负载均衡是基于Ribbon的所以很快就找到了FeignRibbonClientAutoConfiguration.java 这个类

@ConditionalOnClass({ ILoadBalancer.class, Feign.class })
@Configuration
@AutoConfigureBefore(FeignAutoConfiguration.class)
@EnableConfigurationProperties({ FeignHttpClientProperties.class })
//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({ HttpClientFeignLoadBalancedConfiguration.class,
		OkHttpFeignLoadBalancedConfiguration.class,
		DefaultFeignLoadBalancedConfiguration.class })
public class FeignRibbonClientAutoConfiguration {

首先我们从这三个类进行分析，从名字上来看我为了验证没有特殊配置，feign底层走的是不是默认的DefaultFeignLoadBalancedConfiguration.class

OkHttpFeignLoadBalancedConfiguration.class
HttpClientFeignLoadBalancedConfiguration.class
DefaultFeignLoadBalancedConfiguration.class

DefaultFeignLoadBalancedConfiguration.class

@Configuration
class DefaultFeignLoadBalancedConfiguration {
	@Bean
	@ConditionalOnMissingBean
	public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,
							  SpringClientFactory clientFactory) {
		return new LoadBalancerFeignClient(new Client.Default(null, null),
				cachingFactory, clientFactory);
	}
}

从上面代码可知每次请求过来都会创建一个新的client,具体的源码演示有兴趣的可以深入研究，在这里不是我们所研究的重点。

OkHttpFeignLoadBalancedConfiguration.class

@Configuration
@ConditionalOnClass(OkHttpClient.class)
@ConditionalOnProperty(value = "feign.okhttp.enabled")
class OkHttpFeignLoadBalancedConfiguration {

	@Configuration
	@ConditionalOnMissingBean(okhttp3.OkHttpClient.class)
	protected static class OkHttpFeignConfiguration {
		private okhttp3.OkHttpClient okHttpClient;

		@Bean
		@ConditionalOnMissingBean(ConnectionPool.class)
		public ConnectionPool httpClientConnectionPool(FeignHttpClientProperties httpClientProperties,
													   OkHttpClientConnectionPoolFactory connectionPoolFactory) {
			Integer maxTotalConnections = httpClientProperties.getMaxConnections();
			Long timeToLive = httpClientProperties.getTimeToLive();
			TimeUnit ttlUnit = httpClientProperties.getTimeToLiveUnit();
			return connectionPoolFactory.create(maxTotalConnections, timeToLive, ttlUnit);
		}

		@Bean
		public okhttp3.OkHttpClient client(OkHttpClientFactory httpClientFactory,
										   ConnectionPool connectionPool, FeignHttpClientProperties httpClientProperties) {
			Boolean followRedirects = httpClientProperties.isFollowRedirects();
			Integer connectTimeout = httpClientProperties.getConnectionTimeout();
			this.okHttpClient = httpClientFactory.createBuilder(httpClientProperties.isDisableSslValidation()).
					connectTimeout(connectTimeout, TimeUnit.MILLISECONDS).
					followRedirects(followRedirects).
					connectionPool(connectionPool).build();
			return this.okHttpClient;
		}

		@PreDestroy
		public void destroy() {
			if(okHttpClient != null) {
				okHttpClient.dispatcher().executorService().shutdown();
				okHttpClient.connectionPool().evictAll();
			}
		}
	}

	@Bean
	@ConditionalOnMissingBean(Client.class)
	public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,
							  SpringClientFactory clientFactory, okhttp3.OkHttpClient okHttpClient) {
		OkHttpClient delegate = new OkHttpClient(okHttpClient);
		return new LoadBalancerFeignClient(delegate, cachingFactory, clientFactory);
	}
}

从源码可以看出

1 该类是个配置类，当引入OkHttpClient.Class会加载
client方法中可以看出会返回一个http连接池的client

HttpClientFeignLoadBalancedConfiguration

@Configuration
@ConditionalOnClass(ApacheHttpClient.class)
@ConditionalOnProperty(value = "feign.httpclient.enabled", matchIfMissing = true)
class HttpClientFeignLoadBalancedConfiguration {

这个类和OkHttpFeignLoadBalancedConfiguration原理类型

使用OKHttp替代默认的JDK的HttpURLConnection

使用appach httpclient使用教程类似

使用方法

1 pom

        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-okhttp</artifactId>
        </dependency>

2 Yml文件

feign:
  okhttp:
    enabled: true

3 自定义连接池
可以通过代码进行配置，也可以通过yml配置

@Configuration
@ConditionalOnClass(Feign.class)
@AutoConfigureBefore(FeignAutoConfiguration.class)
public class FeignOkHttpConfig {
    @Bean
    public okhttp3.OkHttpClient okHttpClient(){
        return new okhttp3.OkHttpClient.Builder()
                .readTimeout(60,TimeUnit.SECONDS)
                .connectTimeout(60,TimeUnit.SECONDS)
                .connectionPool(new ConnectionPool())
                .build();
    }
}

验证

默认的Feign处理会走到如下位置；
位置处于如下图所示

 @Override
    public Response execute(Request request, Options options) throws IOException {
      HttpURLConnection connection = convertAndSend(request, options);
      return convertResponse(connection).toBuilder().request(request).build();
    }

走okhttp客户端会走如下代码
具体位置如下图所示：

@Override public Response execute() throws IOException {
    synchronized (this) {
      if (executed) throw new IllegalStateException("Already Executed");
      executed = true;
    }
    captureCallStackTrace();
    try {
      client.dispatcher().executed(this);
      Response result = getResponseWithInterceptorChain();
      if (result == null) throw new IOException("Canceled");
      return result;
    } finally {
      client.dispatcher().finished(this);
    }
  }

验证结果

如下所示：

彩蛋

okhttp客户端会走的代码可以看出来okhttp有synchronized锁线程安全的那默认的是否是线程安全的呢有待去验证。

追加

如果发现配置的超时时间无效，可以添加以下配置，因为读取超时配置的时候没有读取上面的okhttp的配置参数，而是从Request中读取。具体配置如下所示:

 @Bean
    public Request.Options options(){
        return new Request.Options(60000,60000);
    }

SpringCloud feign的http请求组件优化