Creates a retry filter using reactor-extra

fixes gh-94

spring-cloud-gateway-core/pom.xml

@@ -78,6 +78,10 @@
 			<version>${kotlin.version}</version>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>io.projectreactor.addons</groupId>
+			<artifactId>reactor-extra</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.cloud</groupId>
 			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -53,6 +53,7 @@ import org.springframework.cloud.gateway.filter.factory.RemoveNonProxyHeadersGat
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestRateLimiterGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.RetryGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewritePathGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SaveSessionGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SecureHeadersGatewayFilterFactory;
@@ -380,6 +381,11 @@ public class GatewayAutoConfiguration {
 		return new RewritePathGatewayFilterFactory();
 	}
 
+	@Bean
+	public RetryGatewayFilterFactory retryGatewayFilterFactory() {
+		return new RetryGatewayFilterFactory();
+	}
+
 	@Bean
 	public SetPathGatewayFilterFactory setPathGatewayFilterFactory() {
 		return new SetPathGatewayFilterFactory();

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/RetryGatewayFilterFactory.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2013-2018 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.gateway.filter.factory;
+
+import java.util.function.Predicate;
+
+import org.springframework.http.HttpMethod;
+import reactor.retry.DefaultRepeat;
+import reactor.retry.Repeat;
+import reactor.retry.RepeatContext;
+
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.tuple.Tuple;
+import org.springframework.web.server.ServerWebExchange;
+
+public class RetryGatewayFilterFactory implements GatewayFilterFactory {
+	@Override
+	public GatewayFilter apply(Tuple args) {
+		return (exchange, chain) -> {
+			Predicate<? super RepeatContext<Object>> predicate = context -> {
+				ServerWebExchange ex = (ServerWebExchange) context.applicationContext();
+				boolean retryableStatusCode = ex.getResponse().getStatusCode().is5xxServerError();
+				boolean retryableMethod = ex.getRequest().getMethod().equals(HttpMethod.GET);
+				return retryableMethod && retryableStatusCode;
+			};
+			Repeat<Object> repeat = DefaultRepeat.create(predicate, 4)
+					.withApplicationContext(exchange);
+			return chain.filter(exchange).repeatWhen(repeat).next();
+		};
+	}
+}

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/route/builder/GatewayFilterSpec.java

@@ -38,6 +38,7 @@ import org.springframework.cloud.gateway.filter.factory.RemoveNonProxyHeadersGat
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestRateLimiterGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.RetryGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewritePathGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SaveSessionGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SecureHeadersGatewayFilterFactory;
@@ -202,6 +203,10 @@ public class GatewayFilterSpec extends UriSpec {
 		return filter(getBean(RewritePathGatewayFilterFactory.class).apply(regex, replacement));
 	}
 
+	public GatewayFilterSpec retry() {
+		return filter(getBean(RetryGatewayFilterFactory.class).apply(EMPTY_TUPLE));
+	}
+
 	public GatewayFilterSpec secureHeaders() {
 		return filter(getBean(SecureHeadersGatewayFilterFactory.class).apply(EMPTY_TUPLE));
 	}

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/factory/RetryGatewayFilterFactoryIntegrationTests.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2013-2018 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.gateway.filter.factory;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+public class RetryGatewayFilterFactoryIntegrationTests extends BaseWebClientTests {
+
+	@Test
+	public void retryFilterGet() {
+		testClient.get()
+				.uri("/retry?key=get")
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody(String.class).isEqualTo("3");
+	}
+
+	@Test
+	//TODO: support post
+	public void retryFilterPost() {
+		testClient.post()
+				.uri("/retry?key=post")
+				.exchange()
+				.expectStatus().is5xxServerError();
+				// .expectBody(String.class).isEqualTo("3");
+	}
+
+	@RestController
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+		Log log = LogFactory.getLog(getClass());
+
+		ConcurrentHashMap<String, AtomicInteger> map = new ConcurrentHashMap<>();
+
+		@RequestMapping("/httpbin/retry")
+		public String retry(@RequestParam("key") String key) {
+			AtomicInteger count = map.computeIfAbsent(key, s -> new AtomicInteger());
+			int i = count.incrementAndGet();
+			log.warn("Retry count: "+i);
+			if (i < 3) {
+				throw new RuntimeException("temporarily broken");
+			}
+			return String.valueOf(i);
+		}
+	}
+
+}

spring-cloud-gateway-core/src/test/resources/application.yml

@@ -131,6 +131,14 @@ spring:
         - AddResponseHeader=X-Request-Foo, Bar
         - RemoveResponseHeader=X-Request-Foo
 
+      # =====================================
+      - id: retry_test
+        uri: ${test.uri}
+        predicates:
+        - Path=/retry
+        filters:
+        - Retry
+
       # =====================================
       - id: secure_headers_test
         uri: ${test.uri}