fix: retry interceptor now closes previous response

aws-android-sdk-appsync/build.gradle

@@ -49,6 +49,7 @@ dependencies {
     testImplementation 'org.mockito:mockito-core:3.2.4'
     testImplementation "com.amazonaws:aws-android-sdk-cognitoidentityprovider:$aws_version"
     testImplementation project(':aws-android-sdk-appsync-runtime')
+    testImplementation("com.squareup.okhttp3:mockwebserver:4.3.1")
     implementation ("com.amazonaws:aws-android-sdk-mobile-client:$aws_version@aar") { transitive = true }
     implementation ("com.amazonaws:aws-android-sdk-auth-userpools:$aws_version@aar") { transitive = true }
 

aws-android-sdk-appsync/src/main/java/com/amazonaws/mobileconnectors/appsync/retry/RetryInterceptor.java

@@ -58,6 +58,7 @@ public Response intercept(Chain chain) throws IOException {
             if (retryAfterHeaderValue != null) {
                 try {
                     waitMillis = Integer.parseInt(retryAfterHeaderValue) * 1000;
+                    response.close();
                     continue;
                 } catch (NumberFormatException e) {
                     Log.w(TAG, "Could not parse Retry-After header: " + retryAfterHeaderValue);
@@ -69,6 +70,7 @@ public Response intercept(Chain chain) throws IOException {
             if ((response.code() >= 500 && response.code() < 600)
                     || response.code() == 429 ) {
                 waitMillis = calculateBackoff(retryCount);
+                response.close();
                 continue;
             }
 

aws-android-sdk-appsync/src/test/java/com/amazonaws/mobileconnectors/appsync/retry/RetryInterceptorTest.java

@@ -0,0 +1,133 @@
+/**
+ * Copyright 2021 Amazon.com,,
+ * Inc. or its affiliates. All Rights Reserved.
+ * <p>
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.amazonaws.mobileconnectors.appsync.retry;
+
+import org.jetbrains.annotations.NotNull;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+import java.io.IOException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import okhttp3.Call;
+import okhttp3.Callback;
+import okhttp3.MediaType;
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.RequestBody;
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Tests for retry interceptor.
+ */
+@RunWith(RobolectricTestRunner.class)
+@Config(manifest = "AndroidManifest.xml")
+public class RetryInterceptorTest {
+    public static final int TEST_TIMEOUT = 10;
+    private MockWebServer mockWebServer;
+    private OkHttpClient okHttpClient;
+
+    @Before
+    public void beforeEachTest() throws IOException {
+        mockWebServer = new MockWebServer();
+        mockWebServer.start(8888);
+
+        okHttpClient = new OkHttpClient.Builder()
+            .addInterceptor(new RetryInterceptor())
+            .build();
+    }
+
+    @After
+    public void afterEachTest() throws IOException {
+        mockWebServer.shutdown();
+    }
+
+    /**
+     * Verify that everything works when the first attempt succeeds.
+     * @throws IOException Not expected
+     * @throws InterruptedException Not expected
+     */
+    @Test
+    public void successfulRequestWithoutFailuresTest() throws IOException, InterruptedException {
+        mockWebServer.enqueue(new MockResponse().setResponseCode(200).setBody("{\"result\":\"all good\""));
+
+        Request request = new Request.Builder()
+            .url("http://localhost:8888")
+            .method("POST", RequestBody.create("{}", MediaType.get("application/json")))
+            .build();
+
+        final AtomicBoolean successful = new AtomicBoolean(false);
+        final CountDownLatch requestLatch = new CountDownLatch(1);
+        okHttpClient.newCall(request).enqueue(new Callback() {
+            @Override
+            public void onFailure(@NotNull Call call, @NotNull IOException e) {
+                requestLatch.countDown();
+            }
+
+            @Override
+            public void onResponse(@NotNull Call call, @NotNull okhttp3.Response response) throws IOException {
+                if (response.code() < 300) {
+                    assertTrue(response.body().string().contains("all good"));
+                    successful.set(true);
+                }
+                requestLatch.countDown();
+            }
+        });
+        requestLatch.await(TEST_TIMEOUT, TimeUnit.SECONDS);
+        assertTrue(successful.get());
+    }
+
+    /**
+     * Verify that retries happen successfully without leaving the previous response open.
+     * This test was created as a result of a Github issue
+     * https://github.com/awslabs/aws-mobile-appsync-sdk-android/issues/305.
+     * @throws IOException Not expected
+     * @throws InterruptedException Not expected
+     */
+    @Test
+    public void successfulRequestWithFailuresTest() throws IOException, InterruptedException {
+        mockWebServer.enqueue(new MockResponse().setResponseCode(500).setBody("{\"error\":\"some exception\""));
+        mockWebServer.enqueue(new MockResponse().setResponseCode(501).setBody("{\"error\":\"another exception\"").setHeader("Retry-After", "1"));
+        mockWebServer.enqueue(new MockResponse().setResponseCode(500).setBody("{\"error\":\"some exception\""));
+        mockWebServer.enqueue(new MockResponse().setResponseCode(200).setBody("{\"result\":\"all good\""));
+
+        Request request = new Request.Builder()
+            .url("http://localhost:8888")
+            .method("POST", RequestBody.create("{}", MediaType.get("application/json")))
+            .build();
+
+        final AtomicBoolean successful = new AtomicBoolean(false);
+        final CountDownLatch requestLatch = new CountDownLatch(1);
+        okHttpClient.newCall(request).enqueue(new Callback() {
+            @Override
+            public void onFailure(@NotNull Call call, @NotNull IOException e) {
+                requestLatch.countDown();
+            }
+
+            @Override
+            public void onResponse(@NotNull Call call, @NotNull okhttp3.Response response) throws IOException {
+                if (response.code() < 300) {
+                    assertTrue(response.body().string().contains("all good"));
+                    successful.set(true);
+                }
+                requestLatch.countDown();
+            }
+        });
+        requestLatch.await(10, TimeUnit.SECONDS);
+        assertTrue(successful.get());
+    }
+}