Giving an option to reuse a custom feign client

without this change you couldn't register your own client (for example to set your ssl config) for Sleuth to reuse it
with this change we're reusing a registered feign client bean or creating a default one if necessary

fixes #502

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/feign/FeignBeanPostProcessor.java

@@ -1,48 +0,0 @@
-/*
- * Copyright 2013-2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.springframework.cloud.sleuth.instrument.web.client.feign;
-
-import org.springframework.beans.BeansException;
-import org.springframework.beans.factory.config.BeanPostProcessor;
-
-/**
- * Post processor that wraps Feign related classes in their tracing representations.
- *
- * @author Marcin Grzejszczak
- *
- * @since 1.0.0
- */
-final class FeignBeanPostProcessor implements BeanPostProcessor {
-
-	private final TraceFeignObjectWrapper traceFeignObjectWrapper;
-
-	FeignBeanPostProcessor(TraceFeignObjectWrapper traceFeignObjectWrapper) {
-		this.traceFeignObjectWrapper = traceFeignObjectWrapper;
-	}
-
-	@Override
-	public Object postProcessBeforeInitialization(Object bean, String beanName)
-			throws BeansException {
-		return this.traceFeignObjectWrapper.wrap(bean);
-	}
-
-	@Override
-	public Object postProcessAfterInitialization(Object bean, String beanName)
-			throws BeansException {
-		return bean;
-	}
-}

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/feign/TraceFeignAspect.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2013-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.sleuth.instrument.web.client.feign;
+
+import org.aspectj.lang.ProceedingJoinPoint;
+import org.aspectj.lang.annotation.Around;
+import org.aspectj.lang.annotation.Aspect;
+import org.springframework.beans.factory.BeanFactory;
+
+import feign.Client;
+import feign.Request;
+
+/**
+ * Aspect for Feign clients so that you can autowire your custom components
+ *
+ * @author Marcin Grzejszczak
+ * @since 1.1.2
+ */
+@Aspect
+class TraceFeignAspect {
+
+	private final BeanFactory beanFactory;
+
+	TraceFeignAspect(BeanFactory beanFactory) {
+		this.beanFactory = beanFactory;
+	}
+
+	@Around("execution (* feign.Client.*(..))")
+	public Object feignClientWasCalled(final ProceedingJoinPoint pjp) throws Throwable {
+		Object[] args = pjp.getArgs();
+		Request request = (Request) args[0];
+		Request.Options options = (Request.Options) args[1];
+		Object bean = pjp.getTarget();
+		if (!(bean instanceof TraceFeignClient)) {
+			return new TraceFeignClient(this.beanFactory, (Client) bean).execute(request, options);
+		}
+		return pjp.proceed();
+	}
+}

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/feign/TraceFeignClient.java

@@ -25,6 +25,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.cloud.sleuth.instrument.web.HttpSpanInjector;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.Tracer;
 import org.springframework.cloud.sleuth.instrument.web.HttpTraceKeysInjector;
@@ -54,7 +55,15 @@ class TraceFeignClient implements Client {
 
 	TraceFeignClient(BeanFactory beanFactory) {
 		this.beanFactory = beanFactory;
-		this.delegate = new Client.Default(null, null);
+		this.delegate = client(beanFactory);
+	}
+
+	private Client client(BeanFactory beanFactory) {
+		try {
+			return beanFactory.getBean(Client.class);
+		} catch (NoSuchBeanDefinitionException e) {
+			return new Client.Default(null, null);
+		}
 	}
 
 	TraceFeignClient(BeanFactory beanFactory, Client delegate) {

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/feign/TraceFeignClientAutoConfiguration.java

@@ -60,7 +60,7 @@ public class TraceFeignClientAutoConfiguration {
 	@Bean
 	@ConditionalOnMissingBean
 	@Scope("prototype")
-	@ConditionalOnProperty(name = "feign.hystrix.enabled", havingValue = "false", matchIfMissing = false)
+	@ConditionalOnProperty(name = "feign.hystrix.enabled", havingValue = "false")
 	Feign.Builder feignBuilder(BeanFactory beanFactory) {
 		return SleuthFeignBuilder.builder(beanFactory);
 	}
@@ -69,11 +69,6 @@ public class TraceFeignClientAutoConfiguration {
 	@ConditionalOnProperty(name = "spring.sleuth.feign.processor.enabled", matchIfMissing = true)
 	protected static class FeignBeanPostProcessorConfiguration {
 
-		@Bean
-		FeignBeanPostProcessor feignBeanPostProcessor(TraceFeignObjectWrapper traceFeignObjectWrapper) {
-			return new FeignBeanPostProcessor(traceFeignObjectWrapper);
-		}
-
 		@Bean
 		FeignContextBeanPostProcessor feignContextBeanPostProcessor(BeanFactory beanFactory) {
 			return new FeignContextBeanPostProcessor(beanFactory);
@@ -84,4 +79,9 @@ public class TraceFeignClientAutoConfiguration {
 	TraceFeignObjectWrapper traceFeignObjectWrapper(BeanFactory beanFactory) {
 		return new TraceFeignObjectWrapper(beanFactory);
 	}
+
+	@Bean
+	TraceFeignAspect traceFeignAspect(BeanFactory beanFactory) {
+		return new TraceFeignAspect(beanFactory);
+	}
 }

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/feign/TraceLoadBalancerFeignClient.java

@@ -1,19 +1,11 @@
 package org.springframework.cloud.sleuth.instrument.web.client.feign;
 
-import java.io.IOException;
-import java.lang.invoke.MethodHandles;
-
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.cloud.netflix.feign.ribbon.CachingSpringLoadBalancerFactory;
 import org.springframework.cloud.netflix.feign.ribbon.LoadBalancerFeignClient;
 import org.springframework.cloud.netflix.ribbon.SpringClientFactory;
-import org.springframework.cloud.sleuth.Tracer;
 
 import feign.Client;
-import feign.Request;
-import feign.Response;
 
 /**
  * We need to wrap the {@link LoadBalancerFeignClient} into a trace representation
@@ -24,31 +16,13 @@ import feign.Response;
  */
 class TraceLoadBalancerFeignClient extends LoadBalancerFeignClient {
 
-	private static final Log log = LogFactory.getLog(MethodHandles.lookup().lookupClass());
-
-	private final BeanFactory beanFactory;
-	private Tracer tracer;
-
 	TraceLoadBalancerFeignClient(Client delegate,
 			CachingSpringLoadBalancerFactory lbClientFactory,
 			SpringClientFactory clientFactory, BeanFactory beanFactory) {
 		super(wrap(delegate, beanFactory), lbClientFactory, clientFactory);
-		this.beanFactory = beanFactory;
-	}
-
-	@Override public Response execute(Request request, Request.Options options)
-			throws IOException {
-		return super.execute(request, options);
 	}
 
 	private static Client wrap(Client delegate, BeanFactory beanFactory) {
 		return (Client) new TraceFeignObjectWrapper(beanFactory).wrap(delegate);
 	}
-
-	private Tracer tracer() {
-		if (this.tracer == null) {
-			this.tracer = this.beanFactory.getBean(Tracer.class);
-		}
-		return this.tracer;
-	}
 }

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/client/feign/issues/issue502/Issue502Tests.java

@@ -0,0 +1,121 @@
+/*
+ * Copyright 2013-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.sleuth.instrument.web.client.feign.issues.issue502;
+
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.util.HashMap;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.netflix.feign.EnableFeignClients;
+import org.springframework.cloud.netflix.feign.FeignClient;
+import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
+import org.springframework.cloud.sleuth.trace.TestSpanContextHolder;
+import org.springframework.cloud.sleuth.util.ExceptionUtils;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+
+import feign.Client;
+import feign.Request;
+import feign.Response;
+
+import static org.assertj.core.api.BDDAssertions.then;
+
+/**
+ * @author Marcin Grzejszczak
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = Application.class,
+		webEnvironment = SpringBootTest.WebEnvironment.NONE,
+		properties = {"feign.hystrix.enabled=false"})
+public class Issue502Tests {
+
+	@Autowired MyClient myClient;
+	@Autowired MyNameRemote myNameRemote;
+
+	@Before
+	public void open() {
+		TestSpanContextHolder.removeCurrentSpan();
+		ExceptionUtils.setFail(true);
+	}
+
+	@After
+	public void close() {
+		TestSpanContextHolder.removeCurrentSpan();
+	}
+
+	@Test
+	public void should_reuse_custom_feign_client() {
+		String response = this.myNameRemote.get();
+
+		then(this.myClient.wasCalled()).isTrue();
+		then(response).isEqualTo("foo");
+		then(ExceptionUtils.getLastException()).isNull();
+	}
+}
+
+@Configuration
+@EnableAutoConfiguration
+@EnableFeignClients
+class Application {
+
+	@Bean
+	public Client client() {
+		return new MyClient();
+	}
+
+	@Bean
+	public AlwaysSampler defaultSampler() {
+		return new AlwaysSampler();
+	}
+
+}
+
+@FeignClient(name="foo",
+		url="http://non.existing.url")
+interface MyNameRemote {
+
+	@RequestMapping(value = "/", method = RequestMethod.GET)
+	String get();
+}
+
+class MyClient implements Client {
+
+	boolean wasCalled;
+
+	@Override public Response execute(Request request, Request.Options options)
+			throws IOException {
+		this.wasCalled = true;
+		return Response.builder()
+				.body("foo", Charset.forName("UTF-8"))
+				.headers(new HashMap<>())
+				.status(200).build();
+	}
+
+	boolean wasCalled() {
+		return this.wasCalled;
+	}
+}