BAEL-5301 Retrying Feign Calls

feign/src/main/java/com/baeldung/feign/retry/Custom5xxErrorDecoder.java

@@ -0,0 +1,27 @@
+package com.baeldung.feign.retry;
+
+
+import feign.FeignException;
+import feign.Response;
+import feign.RetryableException;
+import feign.codec.ErrorDecoder;
+
+import static feign.FeignException.errorStatus;
+
+public class Custom5xxErrorDecoder implements ErrorDecoder {
+    @Override
+    public Exception decode(String methodKey, Response response) {
+        FeignException exception = errorStatus(methodKey, response);
+        int status = response.status();
+        if (status >= 500) {
+            return new RetryableException(
+                    response.status(),
+                    exception.getMessage(),
+                    response.request().httpMethod(),
+                    exception,
+                    null,
+                    response.request());
+        }
+        return exception;
+    }
+}

feign/src/main/java/com/baeldung/feign/retry/NaiveRetryer.java

@@ -0,0 +1,21 @@
+package com.baeldung.feign.retry;
+
+import feign.RetryableException;
+import feign.Retryer;
+
+public class NaiveRetryer implements feign.Retryer {
+    @Override
+    public void continueOrPropagate(RetryableException e) {
+        try {
+            Thread.sleep(1000L);
+        } catch (InterruptedException ex) {
+            Thread.currentThread().interrupt();
+            throw e;
+        }
+    }
+
+    @Override
+    public Retryer clone() {
+        return new NaiveRetryer();
+    }
+}

feign/src/main/java/com/baeldung/feign/retry/ResilientFeignClientBuilder.java

@@ -0,0 +1,28 @@
+package com.baeldung.feign.retry;
+
+import com.baeldung.feign.clients.BookClient;
+import feign.Feign;
+import feign.Logger;
+import feign.Retryer;
+import feign.gson.GsonDecoder;
+import feign.gson.GsonEncoder;
+import feign.okhttp.OkHttpClient;
+import feign.slf4j.Slf4jLogger;
+import lombok.Getter;
+
+import java.util.concurrent.TimeUnit;
+
+@Getter
+public class ResilientFeignClientBuilder {
+    public BookClient bookClient = createClient(BookClient.class, "http://localhost:8081/api/books");
+
+    public static <T> T createClient(Class<T> type, String uri) {
+        return Feign.builder()
+            .client(new OkHttpClient())
+            .encoder(new GsonEncoder())
+            .decoder(new GsonDecoder())
+            .retryer(new Retryer.Default(100L, TimeUnit.SECONDS.toMillis(3L), 5))
+            .errorDecoder(new Custom5xxErrorDecoder())
+            .target(type, uri);
+    }
+}

feign/src/test/java/com/baeldung/feign/retry/Custom5xxErrorDecoderUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.feign.retry;
+
+import feign.*;
+import feign.codec.ErrorDecoder;
+import org.jetbrains.annotations.NotNull;
+import org.junit.Test;
+
+import java.nio.charset.Charset;
+import java.util.Collection;
+import java.util.HashMap;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class Custom5xxErrorDecoderUnitTest {
+    @Test
+    public void given5xxResponse_whenDecode_thenReturnRetryableException() {
+        // given
+        ErrorDecoder decoder = new Custom5xxErrorDecoder();
+        Response response = responseStub(500);
+
+        // when
+        Exception exception = decoder.decode("GET", response);
+
+        // then
+        assertTrue(exception instanceof RetryableException);
+    }
+
+    @Test
+    public void given4xxResponse_whenDecode_thenReturnFeignException() {
+        // given
+        ErrorDecoder decoder = new Custom5xxErrorDecoder();
+        Response response = responseStub(400);
+
+        // when
+        Exception exception = decoder.decode("GET", response);
+
+        // then
+        assertTrue(exception instanceof FeignException);
+        assertFalse(exception instanceof RetryableException);
+    }
+
+    @NotNull
+    private Response responseStub(int status) {
+        return Response.builder()
+                .request(Request.create(
+                        Request.HttpMethod.GET, "url", new HashMap<String, Collection<String>>(), new byte[0], Charset.defaultCharset(), new RequestTemplate()))
+                .status(status)
+                .build();
+    }
+}