Fix gRPC Retry Mechanism for Unsuccessful HTTP Responses

exporters/sender/okhttp/src/main/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpGrpcSender.java

@@ -201,14 +201,12 @@ public CompletableResultCode shutdown() {
 
   /** Whether response is retriable or not. */
   public static boolean isRetryable(Response response) {
-    // Only retry on gRPC codes which will always come with an HTTP success
-    if (!response.isSuccessful()) {
-      return false;
-    }
-
     // We don't check trailers for retry since retryable error codes always come with response
     // headers, not trailers, in practice.
     String grpcStatus = response.header(GRPC_STATUS);
+    if (grpcStatus == null) {
+      return false;
+    }
     return RetryUtil.retryableGrpcStatusCodes().contains(grpcStatus);
   }
 

exporters/sender/okhttp/src/test/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpGrpcSenderTest.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.exporter.sender.okhttp.internal;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import io.opentelemetry.exporter.internal.RetryUtil;
+import io.opentelemetry.exporter.internal.grpc.GrpcExporterUtil;
+import java.util.Set;
+import okhttp3.MediaType;
+import okhttp3.Protocol;
+import okhttp3.Request;
+import okhttp3.Response;
+import okhttp3.ResponseBody;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+public class OkHttpGrpcSenderTest {
+
+  private static final String GRPC_STATUS = "grpc-status";
+  private static final MediaType TEXT_PLAIN = MediaType.get("text/plain");
+
+  static Set<String> provideRetryableGrpcStatusCodes() {
+    return RetryUtil.retryableGrpcStatusCodes();
+  }
+
+  @ParameterizedTest(name = "isRetryable should return true for GRPC status code: {0}")
+  @MethodSource("provideRetryableGrpcStatusCodes")
+  public void isRetryable_RetryableGrpcStatus(String retryableGrpcStatus) {
+    Response response = createResponse(503, retryableGrpcStatus, "Retryable");
+    boolean isRetryable = OkHttpGrpcSender.isRetryable(response);
+    assertTrue(isRetryable);
+  }
+
+  @Test
+  public void isRetryable_NonRetryableGrpcStatus() {
+    String nonRetryableGrpcStatus =
+        Integer.valueOf(GrpcExporterUtil.GRPC_STATUS_UNKNOWN).toString(); // INVALID_ARGUMENT
+    Response response = createResponse(503, nonRetryableGrpcStatus, "Non-retryable");
+    boolean isRetryable = OkHttpGrpcSender.isRetryable(response);
+    assertFalse(isRetryable);
+  }
+
+  private static Response createResponse(int httpCode, String grpcStatus, String message) {
+    return new Response.Builder()
+        .request(new Request.Builder().url("http://localhost/").build())
+        .protocol(Protocol.HTTP_2)
+        .code(httpCode)
+        .body(ResponseBody.create("body", TEXT_PLAIN))
+        .message(message)
+        .header(GRPC_STATUS, grpcStatus)
+        .build();
+  }
+}