From 5cb5af553e113cbcd44020ef5c4c786a239d0596 Mon Sep 17 00:00:00 2001
From: Nicola Dardanis <ndardanis@adobe.com>
Date: Tue, 14 Feb 2023 12:56:07 +0100
Subject: [PATCH] feat: enhance Feign utility using resiliency4j retries

---
 core/pom.xml                                  |  8 +++
 .../com/adobe/aio/util/feign/FeignUtil.java   | 52 +++++++++++++++++--
 .../adobe/aio/ims/feign/FeignImsService.java  |  1 +
 pom.xml                                       | 12 +++++
 4 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/core/pom.xml b/core/pom.xml
index 2531c941..5052b74b 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -54,6 +54,14 @@
       <groupId>io.github.openfeign.form</groupId>
       <artifactId>feign-form</artifactId>
     </dependency>
+    <dependency>
+      <groupId>io.github.resilience4j</groupId>
+      <artifactId>resilience4j-feign</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>io.github.resilience4j</groupId>
+      <artifactId>resilience4j-retry</artifactId>
+    </dependency>
     <dependency>
       <groupId>io.openapitools.jackson.dataformat</groupId>
       <artifactId>jackson-dataformat-hal</artifactId>
diff --git a/core/src/main/java/com/adobe/aio/util/feign/FeignUtil.java b/core/src/main/java/com/adobe/aio/util/feign/FeignUtil.java
index b3bac24c..5ad38ce4 100644
--- a/core/src/main/java/com/adobe/aio/util/feign/FeignUtil.java
+++ b/core/src/main/java/com/adobe/aio/util/feign/FeignUtil.java
@@ -15,17 +15,26 @@
 import feign.Feign;
 import feign.Logger.Level;
 import feign.Request;
+import feign.RetryableException;
+import feign.Retryer;
 import feign.form.FormEncoder;
 import feign.jackson.JacksonDecoder;
 import feign.jackson.JacksonEncoder;
 import feign.optionals.OptionalDecoder;
 import feign.slf4j.Slf4jLogger;
+import io.github.resilience4j.core.IntervalFunction;
+import io.github.resilience4j.feign.FeignDecorators;
+import io.github.resilience4j.feign.Resilience4jFeign;
+import io.github.resilience4j.retry.Retry;
+import io.github.resilience4j.retry.RetryConfig;
 import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
 
 public class FeignUtil {
 
   public static final int DEFAULT_CONNECT_TIMEOUT_IN_SECONDS = 10;
   public static final int DEFAULT_READ_TIMEOUT_IN_SECONDS = 60;
+  private static final long DEFAULT_RETRY_INITIAL_INTERVAL_IN_MILLISECONDS = 2000;
 
   private FeignUtil() {
   }
@@ -35,10 +44,39 @@ private FeignUtil() {
    * our global read and time out options
    */
   public static Feign.Builder getBaseBuilder() {
-    return Feign.builder()
+    return getBaseBuilder(DEFAULT_RETRY_INITIAL_INTERVAL_IN_MILLISECONDS);
+  }
+
+  public static Feign.Builder getBaseBuilder(long initialIntervalMillis) {
+    final IntervalFunction exponentialBackoff = IntervalFunction
+        .ofExponentialBackoff(initialIntervalMillis, 2.0);
+    FeignDecorators decorators = FeignDecorators.builder()
+        .withRetry(Retry.of("default", RetryConfig.custom()
+            .maxAttempts(3)
+            .retryOnException((t) -> t instanceof RetryableException)
+            .intervalBiFunction((attempt, result) -> result
+                  .bimap(
+                      e -> {
+                        if (e instanceof RetryableException) {
+                          RetryableException ex = (RetryableException) e;
+                          if (ex.retryAfter() != null) {
+                            long interval = System.currentTimeMillis() - ex.retryAfter().getTime();
+                            return Math.max(exponentialBackoff.apply(attempt), interval);
+                          }
+                        }
+                        return exponentialBackoff.apply(attempt);
+                      },
+                      r -> exponentialBackoff.apply(attempt)
+                  )
+                  .fold(Function.identity(), Function.identity())
+            )
+            .build())
+        ).build();
+    return Resilience4jFeign.builder(decorators)
         .logger(new Slf4jLogger())
         //.logLevel(Level.BASIC)
         .logLevel(Level.NONE)
+        .retryer(Retryer.NEVER_RETRY)
         //.logLevel(Level.FULL) // use this instead when debugging
         .decode404()
         .errorDecoder(new IOErrorDecoder())
@@ -51,7 +89,11 @@ public static Feign.Builder getBaseBuilder() {
    * logger and our global read and time out options
    */
   public static Feign.Builder getDefaultBuilder() {
-    return getBaseBuilder()
+    return getDefaultBuilder(DEFAULT_RETRY_INITIAL_INTERVAL_IN_MILLISECONDS);
+  }
+
+  public static Feign.Builder getDefaultBuilder(long initialIntervalMillis) {
+    return getBaseBuilder(initialIntervalMillis)
         .decoder(new OptionalDecoder(new JacksonDecoder(JacksonUtil.DEFAULT_OBJECT_MAPPER)))
         .encoder(new JacksonEncoder(JacksonUtil.DEFAULT_OBJECT_MAPPER));
 
@@ -62,7 +104,11 @@ public static Feign.Builder getDefaultBuilder() {
    * global read and time out options, and form encoder
    */
   public static Feign.Builder getBuilderWithFormEncoder() {
-    return getBaseBuilder()
+    return getBaseBuilder(DEFAULT_RETRY_INITIAL_INTERVAL_IN_MILLISECONDS);
+  }
+
+  public static Feign.Builder getBuilderWithFormEncoder(long initialIntervalMillis) {
+    return getBaseBuilder(initialIntervalMillis)
         .decoder(new OptionalDecoder(new JacksonDecoder(JacksonUtil.DEFAULT_OBJECT_MAPPER)))
         .encoder(new FormEncoder());
   }
diff --git a/ims/src/main/java/com/adobe/aio/ims/feign/FeignImsService.java b/ims/src/main/java/com/adobe/aio/ims/feign/FeignImsService.java
index f5c0ec97..faba4fbe 100644
--- a/ims/src/main/java/com/adobe/aio/ims/feign/FeignImsService.java
+++ b/ims/src/main/java/com/adobe/aio/ims/feign/FeignImsService.java
@@ -17,6 +17,7 @@
 import com.adobe.aio.ims.api.ImsApi;
 import com.adobe.aio.ims.model.AccessToken;
 import com.adobe.aio.util.feign.FeignUtil;
+import feign.Retryer;
 
 public class FeignImsService implements ImsService {
 
diff --git a/pom.xml b/pom.xml
index 432a0a64..7e151051 100644
--- a/pom.xml
+++ b/pom.xml
@@ -113,6 +113,7 @@
 
     <feign.version>11.2</feign.version>
     <feign-form.version>3.8.0</feign-form.version>
+    <resilience4j.version>1.7.0</resilience4j.version>
 
   </properties>
 
@@ -212,6 +213,17 @@
         <version>${feign-form.version}</version>
       </dependency>
 
+      <dependency>
+        <groupId>io.github.resilience4j</groupId>
+        <artifactId>resilience4j-feign</artifactId>
+        <version>${resilience4j.version}</version>
+      </dependency>
+      <dependency>
+        <groupId>io.github.resilience4j</groupId>
+        <artifactId>resilience4j-retry</artifactId>
+        <version>${resilience4j.version}</version>
+      </dependency>
+
       <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>