Adding new logic to send user-agent in S3 Requests

With this commit, we will send s3connectorframework user-agent in
every S3 request to help with observability. This commit also
introduces ObjectClientConfiguration to let uses to prepend user-agent
with custom values.

object-client/src/main/java/com/amazon/connector/s3/ObjectClientConfiguration.java

@@ -0,0 +1,29 @@
+package com.amazon.connector.s3;
+
+import lombok.Builder;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+
+/** Configuration for {@link ObjectClient} */
+@Getter
+@Builder
+@EqualsAndHashCode
+public class ObjectClientConfiguration {
+  private static final String DEFAULT_USER_AGENT_PREFIX = null;
+
+  /** User Agent Prefix. {@link ObjectClientConfiguration#DEFAULT_USER_AGENT_PREFIX} by default. */
+  @Builder.Default private String userAgentPrefix = DEFAULT_USER_AGENT_PREFIX;
+
+  public static final ObjectClientConfiguration DEFAULT =
+      ObjectClientConfiguration.builder().build();
+
+  /**
+   * Construct {@link ObjectClientConfiguration}
+   *
+   * @param userAgentPrefix Prefix to prepend to ObjectClient's userAgent.
+   */
+  @Builder
+  private ObjectClientConfiguration(String userAgentPrefix) {
+    this.userAgentPrefix = userAgentPrefix;
+  }
+}

object-client/src/main/java/com/amazon/connector/s3/S3SdkObjectClient.java

@@ -15,15 +15,37 @@
 
 /** Object client, based on AWS SDK v2 */
 public class S3SdkObjectClient implements ObjectClient, AutoCloseable {
+
+  public static final String HEADER_USER_AGENT = "User-Agent";
+
   private S3AsyncClient s3AsyncClient = null;
+  private ObjectClientConfiguration objectClientConfiguration = null;
+  private final UserAgent userAgent;
 
   /**
-   * Create an instance of a S3 client for interaction with Amazon S3 compatible object stores.
+   * Create an instance of a S3 client, with default configuration, for interaction with Amazon S3
+   * compatible object stores.
    *
    * @param s3AsyncClient Underlying client to be used for making requests to S3.
    */
   public S3SdkObjectClient(@NonNull S3AsyncClient s3AsyncClient) {
+    this(s3AsyncClient, ObjectClientConfiguration.DEFAULT);
+  }
+
+  /**
+   * Create an instance of a S3 client, for interaction with Amazon S3 compatible object stores.
+   *
+   * @param s3AsyncClient Underlying client to be used for making requests to S3.
+   * @param objectClientConfiguration Configuration for object client.
+   */
+  public S3SdkObjectClient(
+      @NonNull S3AsyncClient s3AsyncClient,
+      @NonNull ObjectClientConfiguration objectClientConfiguration) {
+
     this.s3AsyncClient = s3AsyncClient;
+    this.objectClientConfiguration = objectClientConfiguration;
+    this.userAgent = new UserAgent();
+    this.userAgent.prepend(objectClientConfiguration.getUserAgentPrefix());
   }
 
   @Override
@@ -39,12 +61,17 @@ public void close() {
    */
   @Override
   public CompletableFuture<ObjectMetadata> headObject(HeadRequest headRequest) {
+    HeadObjectRequest.Builder builder =
+        HeadObjectRequest.builder().bucket(headRequest.getBucket()).key(headRequest.getKey());
+
+    // Add User-Agent header to the request.
+    builder.overrideConfiguration(
+        AwsRequestOverrideConfiguration.builder()
+            .putHeader(HEADER_USER_AGENT, this.userAgent.getUserAgent())
+            .build());
+
     return s3AsyncClient
-        .headObject(
-            HeadObjectRequest.builder()
-                .bucket(headRequest.getBucket())
-                .key(headRequest.getKey())
-                .build())
+        .headObject(builder.build())
         .thenApply(
             headObjectResponse ->
                 ObjectMetadata.builder().contentLength(headObjectResponse.contentLength()).build());
@@ -71,7 +98,10 @@ public CompletableFuture<ObjectContent> getObject(GetRequest getRequest) {
       // Temporarily adding range of data requested as a Referrer header to allow for easy analysis
       // of access logs. This is similar to what the Auditing feature in S3A does.
       builder.overrideConfiguration(
-          AwsRequestOverrideConfiguration.builder().putHeader("Referer", range).build());
+          AwsRequestOverrideConfiguration.builder()
+              .putHeader("Referer", range)
+              .putHeader(HEADER_USER_AGENT, this.userAgent.getUserAgent())
+              .build());
     }
 
     return s3AsyncClient

object-client/src/main/java/com/amazon/connector/s3/UserAgent.java

@@ -0,0 +1,33 @@
+package com.amazon.connector.s3;
+
+import java.util.Objects;
+import lombok.Getter;
+
+/** User-Agent to be used by ObjectClients */
+@Getter
+public final class UserAgent {
+  // Hard-coded user-agent string
+  private static final String UA_STRING = "s3connectorframework";
+  // TODO: Get VersionInfo and append it to UA. We need to understand how to create (if we want a)
+  // global version (for InputStream and ObjectClient).
+  private static final String VERSION_INFO = null;
+  /**
+   * Disallowed characters in the user agent token: @see <a
+   * href="https://tools.ietf.org/html/rfc7230#section-3.2.6">RFC 7230</a>
+   */
+  private static final String UA_DENYLIST_REGEX = "[() ,/:;<=>?@\\[\\]{}\\\\]";
+
+  private String userAgent = UA_STRING + ":" + VERSION_INFO;
+
+  /**
+   * @param userAgentPrefix to prepend the default user-agent string
+   */
+  public void prepend(String userAgentPrefix) {
+    if (Objects.nonNull(userAgentPrefix))
+      this.userAgent = sanitizeInput(userAgentPrefix) + "/" + this.userAgent;
+  }
+
+  private static String sanitizeInput(String input) {
+    return input == null ? "unknown" : input.replaceAll(UA_DENYLIST_REGEX, "_");
+  }
+}

object-client/src/test/java/com/amazon/connector/s3/S3SdkObjectClientTest.java

@@ -53,6 +53,13 @@ void testConstructorWithWrappedClient() {
     assertNotNull(client);
   }
 
+  @Test
+  void testConstructorWithConfiguration() {
+    ObjectClientConfiguration configuration = ObjectClientConfiguration.DEFAULT;
+    S3SdkObjectClient client = new S3SdkObjectClient(s3AsyncClient, configuration);
+    assertNotNull(client);
+  }
+
   @Test
   void testConstructorThrowsOnNullArgument() {
     assertThrows(

object-client/src/test/java/com/amazon/connector/s3/UserAgentTest.java

@@ -0,0 +1,37 @@
+package com.amazon.connector.s3;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+public class UserAgentTest {
+
+  @Test
+  void testDefaultUserAgent() {
+    UserAgent agent = new UserAgent();
+    assertNotNull(agent.getUserAgent());
+  }
+
+  @Test
+  void testPrependUserAgent() {
+    UserAgent agent = new UserAgent();
+    agent.prepend("unit_test");
+    assertTrue(agent.getUserAgent().startsWith("unit_test"));
+  }
+
+  @Test
+  void testNullPrependIsNoop() {
+    UserAgent agent = new UserAgent();
+    String pre = agent.getUserAgent();
+    agent.prepend(null);
+    String pos = agent.getUserAgent();
+    assertEquals(pre, pos);
+  }
+
+  @Test
+  void testInvalidInputIsSanitised() {
+    UserAgent agent = new UserAgent();
+    agent.prepend("unit/test");
+    assertTrue(agent.getUserAgent().startsWith("unit_test"));
+  }
+}