Addressing PR feedback

Author: S-Saranya1

core/aws-core/src/test/java/software/amazon/awssdk/awscore/internal/defaultsmode/AutoDefaultsModeDiscoveryEc2MetadataClientTest.java

@@ -28,7 +28,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 
 import com.github.tomakehurst.wiremock.junit5.WireMockExtension;
-import java.lang.reflect.Field;
+import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
@@ -58,6 +58,11 @@ static void setupClass() {
                            "http://localhost:" + wireMock.getPort());
     }
 
+    @AfterAll
+    static void cleanupClass() {
+        System.clearProperty(SdkSystemSetting.AWS_EC2_METADATA_SERVICE_ENDPOINT.property());
+    }
+
     @BeforeEach
     public void setup() {
         clearEnvironmentVariable("AWS_EXECUTION_ENV");

core/imds/src/main/java/software/amazon/awssdk/imds/internal/DefaultEc2MetadataClientWithFallback.java

@@ -17,6 +17,8 @@
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
+import java.net.URI;
+import java.time.Duration;
 import java.time.Instant;
 import java.util.Optional;
 import java.util.concurrent.TimeUnit;
@@ -326,8 +328,8 @@ private Token getToken() {
     protected static final class Ec2MetadataBuilder implements Ec2MetadataClient.Builder {
 
         private Ec2MetadataRetryPolicy retryPolicy;
-        private java.net.URI endpoint;
-        private java.time.Duration tokenTtl;
+        private URI endpoint;
+        private Duration tokenTtl;
         private EndpointMode endpointMode;
         private SdkHttpClient httpClient;
         private SdkHttpClient.Builder<?> httpClientBuilder;

core/imds/src/main/java/software/amazon/awssdk/imds/internal/Ec2MetadataSharedClient.java

@@ -16,6 +16,8 @@
 package software.amazon.awssdk.imds.internal;
 
 import java.time.Duration;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 import software.amazon.awssdk.annotations.SdkProtectedApi;
 import software.amazon.awssdk.core.internal.http.loader.DefaultSdkHttpClientBuilder;
 import software.amazon.awssdk.http.SdkHttpClient;
@@ -31,6 +33,7 @@
 @SdkProtectedApi
 public final class Ec2MetadataSharedClient {
 
+    private static final Lock LOCK = new ReentrantLock();
     private static volatile SdkHttpClient sharedHttpClient;
     private static int referenceCount = 0;
 
@@ -56,11 +59,16 @@ public static Ec2MetadataClient create() {
     /**
      * Decrements the reference count and closes the shared HTTP client if no more references exist.
      */
-    public static synchronized void decrementAndClose() {
-        referenceCount--;
-        if (referenceCount == 0 && sharedHttpClient != null) {
-            sharedHttpClient.close();
-            sharedHttpClient = null;
+    public static void decrementAndClose() {
+        LOCK.lock();
+        try {
+            referenceCount--;
+            if (referenceCount == 0 && sharedHttpClient != null) {
+                sharedHttpClient.close();
+                sharedHttpClient = null;
+            }
+        } finally {
+            LOCK.unlock();
         }
     }
 
@@ -80,23 +88,27 @@ public static final class Builder {
         private Builder() {
         }
 
-        public synchronized Builder retryPolicy(Ec2MetadataRetryPolicy retryPolicy) {
+        public Builder retryPolicy(Ec2MetadataRetryPolicy retryPolicy) {
             this.retryPolicy = retryPolicy;
             return this;
         }
 
-        public synchronized Ec2MetadataClient build() {
+        public Ec2MetadataClient build() {
+            LOCK.lock();
+            try {
+                if (sharedHttpClient == null) {
+                    sharedHttpClient = createImdsHttpClient();
+                }
 
-            if (sharedHttpClient == null) {
-                sharedHttpClient = createImdsHttpClient();
+                referenceCount++;
+                
+                return DefaultEc2MetadataClientWithFallback.builder()
+                                                           .httpClient(sharedHttpClient)
+                                                           .retryPolicy(retryPolicy)
+                                                           .build();
+            } finally {
+                LOCK.unlock();
             }
-
-            referenceCount++;
-            
-            return DefaultEc2MetadataClientWithFallback.builder()
-                .httpClient(sharedHttpClient)
-                .retryPolicy(retryPolicy)
-                .build();
         }
     }
 }

core/imds/src/main/java/software/amazon/awssdk/imds/internal/RequestMarshaller.java

@@ -50,7 +50,7 @@ public RequestMarshaller(URI basePath) {
     }
 
     public SdkHttpFullRequest createTokenRequest(Duration tokenTtl) {
-        return defaulttHttpBuilder()
+        return defaultHttpBuilder()
             .method(SdkHttpMethod.PUT)
             .uri(tokenPath)
             .putHeader(EC2_METADATA_TOKEN_TTL_HEADER, String.valueOf(tokenTtl.getSeconds()))
@@ -59,7 +59,7 @@ public SdkHttpFullRequest createTokenRequest(Duration tokenTtl) {
 
     public SdkHttpFullRequest createDataRequest(String path, String token, Duration tokenTtl) {
         URI resourcePath = URI.create(basePath + path);
-        SdkHttpFullRequest.Builder builder = defaulttHttpBuilder()
+        SdkHttpFullRequest.Builder builder = defaultHttpBuilder()
             .method(SdkHttpMethod.GET)
             .uri(resourcePath)
             .putHeader(EC2_METADATA_TOKEN_TTL_HEADER, String.valueOf(tokenTtl.getSeconds()));
@@ -69,7 +69,7 @@ public SdkHttpFullRequest createDataRequest(String path, String token, Duration
         return builder.build();
     }
 
-    private SdkHttpFullRequest.Builder defaulttHttpBuilder() {
+    private SdkHttpFullRequest.Builder defaultHttpBuilder() {
         return SdkHttpFullRequest.builder()
                              .putHeader(USER_AGENT, SystemUserAgent.getOrCreate().userAgentString())
                              .putHeader(ACCEPT, "*/*")

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/loader/DefaultSdkHttpClientBuilder.java

@@ -23,6 +23,9 @@
 
 /**
  * Utility to load the default HTTP client factory and create an instance of {@link SdkHttpClient}.
+ *
+ * Implementation notes: this class should've been outside internal package,
+ * but we can't fix it due to backwards compatibility reasons.
  */
 @SdkProtectedApi
 public final class DefaultSdkHttpClientBuilder implements SdkHttpClient.Builder {