OpenFeign · codefromthecrypt · Oct 16, 2015 · Oct 16, 2015 · codefromthecrypt · Oct 16, 2015
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,6 @@
+### Version 8.11
+* Adds support for Hystrix via a `HystrixFeign` builder.
+
 ### Version 8.10
 * Adds HTTP status to FeignException for easier response handling
 * Reads class-level @Produces/@Consumes JAX-RS annotations

diff --git a/README.md b/README.md
@@ -152,6 +152,16 @@ MyService api = Feign.builder().client(RibbonClient.create()).target(MyService.c
 
 ```
 
+### Hystrix
+[HystrixFeign](https://github.com/Netflix/feign/tree/master/hystrix) configures circuit breaker support provided by [Hystrix](https://github.com/Netflix/Hystrix).
+
+To use Hystrix with Feign, add the Hystrix module to your classpath. Then use the `HystrixFeign` builder:
+
+```java
+MyService api = HystrixFeign.builder().target(MyService.class, "https://myAppProd");
+
+```
+
 ### SLF4J
 [SLF4JModule](https://github.com/Netflix/feign/tree/master/slf4j) allows directing Feign's logging to [SLF4J](http://www.slf4j.org/), allowing you to easily use a logging backend of your choice (Logback, Log4J, etc.)
 

diff --git a/core/src/main/java/feign/MethodMetadata.java b/core/src/main/java/feign/MethodMetadata.java
@@ -50,7 +50,7 @@ public String configKey() {
     return configKey;
   }
 
-  MethodMetadata configKey(String configKey) {
+  public MethodMetadata configKey(String configKey) {
     this.configKey = configKey;
     return this;
   }
@@ -59,7 +59,7 @@ public Type returnType() {
     return returnType;
   }
 
-  MethodMetadata returnType(Type returnType) {
+  public MethodMetadata returnType(Type returnType) {
     this.returnType = returnType;
     return this;
   }
@@ -68,7 +68,7 @@ public Integer urlIndex() {
     return urlIndex;
   }
 
-  MethodMetadata urlIndex(Integer urlIndex) {
+  public MethodMetadata urlIndex(Integer urlIndex) {
     this.urlIndex = urlIndex;
     return this;
   }
@@ -77,7 +77,7 @@ public Integer bodyIndex() {
     return bodyIndex;
   }
 
-  MethodMetadata bodyIndex(Integer bodyIndex) {
+  public MethodMetadata bodyIndex(Integer bodyIndex) {
     this.bodyIndex = bodyIndex;
     return this;
   }
@@ -89,7 +89,7 @@ public Type bodyType() {
     return bodyType;
   }
 
-  MethodMetadata bodyType(Type bodyType) {
+  public MethodMetadata bodyType(Type bodyType) {
     this.bodyType = bodyType;
     return this;
   }

diff --git a/hystrix/README.md b/hystrix/README.md
@@ -0,0 +1,40 @@
+Hystrix
+===================
+
+This module wraps Feign's http requests in [Hystrix](https://github.com/Netflix/Hystrix/), which enables the [Circuit Breaker Pattern](https://en.wikipedia.org/wiki/Circuit_breaker_design_pattern).
+
+To use Hystrix with Feign, add the Hystrix module to your classpath. Then, configure Feign to use the `HystrixInvocationHandler`:
+
+```java
+GitHub github = HystrixFeign.builder()
+        .target(GitHub.class, "https://api.github.com");
+```
+
+Methods that do *not* return [`HystrixCommand`](https://netflix.github.io/Hystrix/javadoc/com/netflix/hystrix/HystrixCommand.html) are still wrapped in a `HystrixCommand`, but `execute()` is automatically called for you.
+
+For asynchronous or reactive use, return `HystrixCommand<YourType>` rather than just `YourType`.
+
+```java
+interface YourApi {
+  @RequestLine("GET /yourtype/{id}")
+  HystrixCommand<YourType> getYourType(@Param("id") String id);
+
+  @RequestLine("GET /yourtype/{id}")
+  YourType getYourTypeSynchronous(@Param("id") String id);
+}
+
+YourApi api = HystrixFeign.builder()
+                  .target(YourApi.class, "https://example.com");
+
+// for reactive
+api.getYourType("a").toObservable();
+
+// for asynchronous
+api.getYourType("a").queue();
+
+// for synchronous
+api.getYourType("a").execute();
+
+// or to apply hystrix to existing feign methods.
+api.getYourTypeSynchronous("a");
+``` 
diff --git a/hystrix/build.gradle b/hystrix/build.gradle
@@ -0,0 +1,13 @@
+apply plugin: 'java'
+
+sourceCompatibility = 1.6
+
+dependencies {
+    compile project(':feign-core')
+    compile 'com.netflix.hystrix:hystrix-core:1.4.18'
+    testCompile 'junit:junit:4.12'
+    testCompile 'org.assertj:assertj-core:1.7.1' // last version supporting JDK 7
+    testCompile 'com.squareup.okhttp:mockwebserver:2.5.0'
+    testCompile project(':feign-gson')
+    testCompile project(':feign-core').sourceSets.test.output // for assertions
+}
diff --git a/hystrix/src/main/java/feign/hystrix/HystrixDelegatingContract.java b/hystrix/src/main/java/feign/hystrix/HystrixDelegatingContract.java
@@ -0,0 +1,37 @@
+package feign.hystrix;
+
+import static feign.Util.resolveLastTypeParameter;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.List;
+
+import com.netflix.hystrix.HystrixCommand;
+
+import feign.Contract;
+import feign.MethodMetadata;
+
+final class HystrixDelegatingContract implements Contract {
+
+  private final Contract delegate;
+
+  public HystrixDelegatingContract(Contract delegate) {
+    this.delegate = delegate;
+  }
+
+  @Override
+  public List<MethodMetadata> parseAndValidatateMetadata(Class<?> targetType) {
+    List<MethodMetadata> metadatas = this.delegate.parseAndValidatateMetadata(targetType);
+
+    for (MethodMetadata metadata : metadatas) {
+      Type type = metadata.returnType();
+
+      if (type instanceof ParameterizedType && ((ParameterizedType) type).getRawType().equals(HystrixCommand.class)) {
+        Type actualType = resolveLastTypeParameter(type, HystrixCommand.class);
+        metadata.returnType(actualType);
+      }
+    }
+
+    return metadatas;
+  }
+}
diff --git a/hystrix/src/main/java/feign/hystrix/HystrixFeign.java b/hystrix/src/main/java/feign/hystrix/HystrixFeign.java
@@ -0,0 +1,30 @@
+package feign.hystrix;
+
+import com.netflix.hystrix.HystrixCommand;
+
+import feign.Contract;
+import feign.Feign;
+
+/**
+ * Allows Feign interfaces to return HystrixCommand objects.
+ * Also decorates normal Feign methods with circuit breakers, but calls {@link HystrixCommand#execute()} directly.
+ */
+public final class HystrixFeign {
+
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  public static final class Builder extends Feign.Builder {
+
+    public Builder() {
+      invocationHandlerFactory(new HystrixInvocationHandler.Factory());
+      contract(new HystrixDelegatingContract(new Contract.Default()));
+    }
+
+    @Override
+    public Feign.Builder contract(Contract contract) {
+      return super.contract(new HystrixDelegatingContract(contract));
+    }
+  }
+}
diff --git a/hystrix/src/main/java/feign/hystrix/HystrixInvocationHandler.java b/hystrix/src/main/java/feign/hystrix/HystrixInvocationHandler.java
@@ -0,0 +1,76 @@
+/*
+ * Copyright 2015 Netflix, Inc.
+ *
+ * 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 feign.hystrix;
+
+import static feign.Util.checkNotNull;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.util.Map;
+
+import com.netflix.hystrix.HystrixCommand;
+import com.netflix.hystrix.HystrixCommandGroupKey;
+import com.netflix.hystrix.HystrixCommandKey;
+
+import feign.InvocationHandlerFactory;
+import feign.InvocationHandlerFactory.MethodHandler;
+import feign.Target;
+
+final class HystrixInvocationHandler implements InvocationHandler {
+
+  private final Target target;
+  private final Map<Method, MethodHandler> dispatch;
+
+  HystrixInvocationHandler(Target target, Map<Method, MethodHandler> dispatch) {
+    this.target = checkNotNull(target, "target");
+    this.dispatch = checkNotNull(dispatch, "dispatch");
+  }
+
+  @Override
+  public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable {
+    String groupKey = this.target.name();
+    String commandKey = method.getName();
+    HystrixCommand.Setter setter = HystrixCommand.Setter
+        .withGroupKey(HystrixCommandGroupKey.Factory.asKey(groupKey))
+        .andCommandKey(HystrixCommandKey.Factory.asKey(commandKey));
+
+    HystrixCommand<Object> hystrixCommand = new HystrixCommand<Object>(setter) {
+      @Override
+      protected Object run() throws Exception {
+        try {
+          return HystrixInvocationHandler.this.dispatch.get(method).invoke(args);
+        } catch (Exception e) {
+          throw e;
+        } catch (Throwable t) {
+          throw (Error)t;
+        }
+      }
+    };
+
+    if (HystrixCommand.class.isAssignableFrom(method.getReturnType())) {
+      return hystrixCommand;
+    }
+    return hystrixCommand.execute();
+  }
+
+  static final class Factory implements InvocationHandlerFactory {
+
+    @Override
+    public InvocationHandler create(Target target, Map<Method, MethodHandler> dispatch) {
+      return new HystrixInvocationHandler(target, dispatch);
+    }
+  }
+}
diff --git a/hystrix/src/test/java/feign/hystrix/HystrixBuilderTest.java b/hystrix/src/test/java/feign/hystrix/HystrixBuilderTest.java
@@ -0,0 +1,112 @@
+package feign.hystrix;
+
+import static feign.assertj.MockWebServerAssertions.assertThat;
+
+import java.util.List;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import com.netflix.hystrix.HystrixCommand;
+import com.squareup.okhttp.mockwebserver.MockResponse;
+import com.squareup.okhttp.mockwebserver.MockWebServer;
+
+import feign.Headers;
+import feign.RequestLine;
+import feign.gson.GsonDecoder;
+
+public class HystrixBuilderTest {
+
+  @Rule
+  public final ExpectedException thrown = ExpectedException.none();
+  @Rule
+  public final MockWebServer server = new MockWebServer();
+
+  @Test
+  public void hystrixCommand() {
+    server.enqueue(new MockResponse().setBody("\"foo\""));
+
+    TestInterface api = target();
+
+    HystrixCommand<String> command = api.command();
+
+    assertThat(command).isNotNull();
+    assertThat(command.execute()).isEqualTo("foo");
+  }
+
+  @Test
+  public void hystrixCommandInt() {
+    server.enqueue(new MockResponse().setBody("1"));
+
+    TestInterface api = target();
+
+    HystrixCommand<Integer> command = api.intCommand();
+
+    assertThat(command).isNotNull();
+    assertThat(command.execute()).isEqualTo(new Integer(1));
+  }
+
+  @Test
+  public void hystrixCommandList() {
+    server.enqueue(new MockResponse().setBody("[\"foo\",\"bar\"]"));
+
+    TestInterface api = target();
+
+    HystrixCommand<List<String>> command = api.listCommand();
+
+    assertThat(command).isNotNull();
+    assertThat(command.execute()).hasSize(2).contains("foo", "bar");
+  }
+
+  @Test
+  public void plainString() {
+    server.enqueue(new MockResponse().setBody("\"foo\""));
+
+    TestInterface api = target();
+
+    String string = api.get();
+
+    assertThat(string).isEqualTo("foo");
+  }
+
+  @Test
+  public void plainList() {
+    server.enqueue(new MockResponse().setBody("[\"foo\",\"bar\"]"));
+
+    TestInterface api = target();
+
+    List<String> list = api.getList();
+
+    assertThat(list).isNotNull().hasSize(2).contains("foo", "bar");
+  }
+
+  private TestInterface target() {
+    return HystrixFeign.builder()
+        .decoder(new GsonDecoder())
+        .target(TestInterface.class, "http://localhost:" + server.getPort());
+  }
+
+  interface TestInterface {
+
+    @RequestLine("GET /")
+    @Headers("Accept: application/json")
+    HystrixCommand<List<String>> listCommand();
+
+    @RequestLine("GET /")
+    @Headers("Accept: application/json")
+    HystrixCommand<String> command();
+
+    @RequestLine("GET /")
+    @Headers("Accept: application/json")
+    HystrixCommand<Integer> intCommand();
+
+    @RequestLine("GET /")
+    @Headers("Accept: application/json")
+    String get();
+
+    @RequestLine("GET /")
+    @Headers("Accept: application/json")
+    List<String> getList();
+  }
+}
diff --git a/settings.gradle b/settings.gradle
@@ -1,5 +1,5 @@
 rootProject.name='feign'
-include 'core', 'sax', 'gson', 'httpclient', 'jackson', 'jaxb', 'jaxrs', 'okhttp', 'ribbon', 'slf4j', 'jackson-jaxb'
+include 'core', 'sax', 'gson', 'httpclient', 'jackson', 'jaxb', 'jaxrs', 'okhttp', 'ribbon', 'slf4j', 'jackson-jaxb', 'hystrix'
 
 rootProject.children.each { childProject ->
     childProject.name = 'feign-' + childProject.name