Restore per-attempt retry logging in OkHttpGrpcSender

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

@@ -219,10 +219,21 @@ private void sendAttempt(
                 new Callback() {
                   @Override
                   public void onFailure(Call call, IOException e) {
+                    boolean retryable = retryState != null && retryState.shouldRetryOnException(e);
+                    if (retryState != null && logger.isLoggable(Level.FINER)) {
+                      logger.log(
+                          Level.FINER,
+                          "Attempt "
+                              + attempt
+                              + " failed with "
+                              + (retryable ? "retryable" : "non-retryable")
+                              + " exception",
+                          e);
+                    }
                     if (!call.isCanceled()
                         && retryState != null
                         && retryState.canRetry(attempt)
-                        && retryState.shouldRetryOnException(e)
+                        && retryable
                         && retryState.backoff(OptionalLong.empty())) {
                       sendAttempt(
                           requestBuilder,
@@ -241,10 +252,22 @@ public void onResponse(Call call, Response response) {
                     handleResponse(
                         response,
                         (resolvedResponse, canRetry) -> {
+                          boolean retryable = canRetry && isRetryable(resolvedResponse);
+                          if (retryState != null && logger.isLoggable(Level.FINER)) {
+                            logger.log(
+                                Level.FINER,
+                                "Attempt "
+                                    + attempt
+                                    + " returned "
+                                    + (retryable ? "retryable" : "non-retryable")
+                                    + " response: grpc-status="
+                                    + resolvedResponse.getStatusCode()
+                                    + ", grpc-message="
+                                    + resolvedResponse.getStatusDescription());
+                          }
                           if (retryState != null
                               && retryState.canRetry(attempt)
-                              && canRetry
-                              && isRetryable(resolvedResponse)
+                              && retryable
                               && retryState.backoff(OptionalLong.empty())) {
                             sendAttempt(
                                 requestBuilder,

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

@@ -11,11 +11,13 @@
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import io.github.netmikey.logunit.api.LogCapturer;
 import io.opentelemetry.exporter.internal.RetryUtil;
 import io.opentelemetry.sdk.common.CompletableResultCode;
 import io.opentelemetry.sdk.common.export.GrpcResponse;
 import io.opentelemetry.sdk.common.export.GrpcStatusCode;
 import io.opentelemetry.sdk.common.export.MessageWriter;
+import io.opentelemetry.sdk.common.export.RetryPolicy;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.net.ServerSocket;
@@ -39,11 +41,17 @@
 import okhttp3.Response;
 import okhttp3.ResponseBody;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.slf4j.event.Level;
+import org.slf4j.event.LoggingEvent;
 
 class OkHttpGrpcSenderTest {
 
+  @RegisterExtension
+  LogCapturer logs = LogCapturer.create().captureForType(OkHttpGrpcSender.class, Level.TRACE);
+
   private static final MediaType GRPC_MEDIA_TYPE = MediaType.get("application/grpc");
 
   static Set<String> provideRetryableGrpcStatusCodes() {
@@ -401,6 +409,45 @@ void constructor_wrapsDefaultTrustManagerFailure() throws Exception {
     }
   }
 
+  @Test
+  void send_retryEnabled_logsEachFailedAttempt() throws Exception {
+    // Allocate an ephemeral port and immediately close it to get a port with nothing listening
+    int port;
+    try (ServerSocket socket = new ServerSocket(0)) {
+      port = socket.getLocalPort();
+    }
+
+    OkHttpGrpcSender sender =
+        new OkHttpGrpcSender(
+            "http://localhost:" + port,
+            null,
+            Duration.ofSeconds(10),
+            Duration.ofSeconds(10),
+            Collections::emptyMap,
+            RetryPolicy.builder().setMaxAttempts(2).setInitialBackoff(Duration.ofMillis(1)).build(),
+            null,
+            null,
+            null,
+            Long.MAX_VALUE,
+            null);
+
+    CompletableResultCode sendResult = new CompletableResultCode();
+    try {
+      sender.send(
+          new TestMessageWriter(), response -> sendResult.succeed(), error -> sendResult.fail());
+      sendResult.join(10, TimeUnit.SECONDS);
+    } finally {
+      sender.shutdown().join(10, TimeUnit.SECONDS);
+    }
+
+    assertThat(sendResult.isSuccess()).isFalse();
+    assertThat(logs.getEvents())
+        .extracting(LoggingEvent::getMessage)
+        .containsExactly(
+            "Attempt 0 failed with retryable exception",
+            "Attempt 1 failed with retryable exception");
+  }
+
   /** Simple test marshaler for testing purposes. */
   private static class TestMessageWriter implements MessageWriter {
     @Override