fix(ffe): handle nullable agentless response bodies

Author: leoromanovsky

dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java

@@ -45,14 +45,13 @@ public final class ConfigDefaults {
   public static final String DEFAULT_SERVLET_ROOT_CONTEXT_SERVICE_NAME = "root-servlet";
   public static final String DEFAULT_AGENT_WRITER_TYPE = "DDAgentWriter";
   public static final boolean DEFAULT_STARTUP_LOGS_ENABLED = true;
-
-  static final boolean DEFAULT_INJECT_DATADOG_ATTRIBUTE = true;
-  static final String DEFAULT_SITE = "datadoghq.com";
-
   public static final String DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE = "agentless";
   public static final int DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE_POLL_INTERVAL_SECONDS = 30;
   public static final int DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE_REQUEST_TIMEOUT_SECONDS = 2;
 
+  static final boolean DEFAULT_INJECT_DATADOG_ATTRIBUTE = true;
+  static final String DEFAULT_SITE = "datadoghq.com";
+
   static final boolean DEFAULT_CODE_ORIGIN_FOR_SPANS_INTERFACE_SUPPORT = false;
   static final int DEFAULT_CODE_ORIGIN_MAX_USER_FRAMES = 8;
   static final boolean DEFAULT_TRACE_ENABLED = true;

products/feature-flagging/feature-flagging-lib/src/main/java/com/datadog/featureflag/AgentlessConfigurationSource.java

@@ -23,6 +23,7 @@
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.DoubleSupplier;
+import javax.annotation.Nullable;
 import okhttp3.Call;
 import okhttp3.HttpUrl;
 import okhttp3.OkHttpClient;
@@ -354,10 +355,10 @@ interface RetrySleeper {
 
   static final class UfcHttpResponse {
     final int status;
-    final String etag;
-    final byte[] body;
+    @Nullable final String etag;
+    @Nullable final byte[] body;
 
-    UfcHttpResponse(final int status, final String etag, final byte[] body) {
+    UfcHttpResponse(final int status, @Nullable final String etag, @Nullable final byte[] body) {
       this.status = status;
       this.etag = etag;
       this.body = body;
@@ -388,9 +389,12 @@ public UfcHttpResponse fetch(final HttpUrl endpoint, final Config config, final
       if (cancelled.get()) {
         call.cancel();
       }
-      try (Response response = call.execute()) {
-        final ResponseBody responseBody = response.body();
-        return new UfcHttpResponse(response.code(), response.header("ETag"), responseBody.bytes());
+      try {
+        final Response response = call.execute();
+        try (ResponseBody responseBody = response.body()) {
+          final byte[] body = responseBody != null ? responseBody.bytes() : null;
+          return new UfcHttpResponse(response.code(), response.header("ETag"), body);
+        }
       } finally {
         activeCall.compareAndSet(call, null);
       }

products/feature-flagging/feature-flagging-lib/src/test/java/com/datadog/featureflag/AgentlessConfigurationSourceTest.java

@@ -13,6 +13,7 @@
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoInteractions;
+import static org.mockito.Mockito.when;
 
 import datadog.communication.http.OkHttpUtils;
 import datadog.logging.RatelimitedLogger;
@@ -35,8 +36,11 @@
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
+import okhttp3.Call;
 import okhttp3.HttpUrl;
 import okhttp3.OkHttpClient;
+import okhttp3.Protocol;
+import okhttp3.Response;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
@@ -191,6 +195,32 @@ void realHttpClientAllowsMissingEtagAndEmptyResponseBody() throws Exception {
     }
   }
 
+  @Test
+  void httpClientAdapterPreservesMissingResponseBody() throws Exception {
+    final OkHttpClient httpClient = mock(OkHttpClient.class);
+    final Call call = mock(Call.class);
+    final HttpUrl endpoint = HttpUrl.get("http://localhost");
+    final okhttp3.Request request = new okhttp3.Request.Builder().url(endpoint).build();
+    final Response okHttpResponse =
+        new Response.Builder()
+            .request(request)
+            .protocol(Protocol.HTTP_1_1)
+            .code(HttpURLConnection.HTTP_OK)
+            .message("OK")
+            .build();
+    when(httpClient.newCall(any())).thenReturn(call);
+    when(call.execute()).thenReturn(okHttpResponse);
+    final AgentlessConfigurationSource.OkHttpUfcHttpClient client =
+        new AgentlessConfigurationSource.OkHttpUfcHttpClient(httpClient);
+
+    final AgentlessConfigurationSource.UfcHttpResponse response =
+        client.fetch(endpoint, config(), null);
+
+    assertEquals(HttpURLConnection.HTTP_OK, response.status);
+    assertNull(response.etag);
+    assertNull(response.body);
+  }
+
   @Test
   void realHttpClientCancellationInterruptsInFlightRequest() throws Exception {
     final CountDownLatch requestStarted = new CountDownLatch(1);