feat(gax): actionable errors logging in ApiTracer framework

gax-java/gax/src/main/java/com/google/api/gax/logging/LoggingUtils.java

@@ -36,11 +36,31 @@
 @InternalApi
 public class LoggingUtils {
 
-  private static boolean loggingEnabled = isLoggingEnabled();
   static final String GOOGLE_SDK_JAVA_LOGGING = "GOOGLE_SDK_JAVA_LOGGING";
 
+  private static boolean loggingEnabled = checkLoggingEnabled(GOOGLE_SDK_JAVA_LOGGING);
+
+  /**
+   * Returns whether client-side logging is enabled.
+   *
+   * @return true if logging is enabled, false otherwise.
+   */
   static boolean isLoggingEnabled() {
-    String enableLogging = System.getenv(GOOGLE_SDK_JAVA_LOGGING);
+    return loggingEnabled;
+  }
+
+  /**
+   * Sets whether client-side logging is enabled. Visible for testing.
+   *
+   * @param enabled true to enable logging, false to disable.
+   */
+  @com.google.common.annotations.VisibleForTesting
+  static void setLoggingEnabled(boolean enabled) {
+    loggingEnabled = enabled;
+  }
+
+  private static boolean checkLoggingEnabled(String envVar) {
+    String enableLogging = System.getenv(envVar);
     return "true".equalsIgnoreCase(enableLogging);
   }
 
@@ -126,6 +146,22 @@ public static <RespT> void logRequest(
     }
   }
 
+  /**
+   * Logs an actionable error message with structured context at a specific log level.
+   *
+   * @param logContext A map containing the structured logging context (e.g., RPC service, method,
+   *     error details).
+   * @param loggerProvider The provider used to obtain the logger.
+   * @param message The human-readable error message.
+   */
+  public static void logActionableError(
+      Map<String, Object> logContext, LoggerProvider loggerProvider, String message) {
+    if (loggingEnabled) {
+      org.slf4j.Logger logger = loggerProvider.getLogger();
+      Slf4jUtils.log(logger, org.slf4j.event.Level.DEBUG, logContext, message);
+    }
+  }
+
   public static void executeWithTryCatch(ThrowingRunnable action) {
     try {
       action.run();

gax-java/gax/src/main/java/com/google/api/gax/tracing/LoggingTracer.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.api.gax.tracing;
+
+import com.google.api.core.BetaApi;
+import com.google.api.core.InternalApi;
+import com.google.api.gax.logging.LoggerProvider;
+import com.google.api.gax.logging.LoggingUtils;
+import com.google.api.gax.rpc.ApiException;
+import com.google.rpc.ErrorInfo;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * An {@link ApiTracer} that logs actionable errors using {@link LoggingUtils} when an RPC attempt
+ * fails.
+ */
+@BetaApi
+@InternalApi
+public class LoggingTracer extends BaseApiTracer {
+  private static final LoggerProvider LOGGER_PROVIDER =
+      LoggerProvider.forClazz(LoggingTracer.class);
+
+  private final ApiTracerContext apiTracerContext;
+
+  public LoggingTracer(ApiTracerContext apiTracerContext) {
+    this.apiTracerContext = apiTracerContext;
+  }
+
+  @Override
+  public void attemptFailed(Throwable error, org.threeten.bp.Duration delay) {
+    recordActionableError(error);
+  }
+
+  @Override
+  public void attemptFailedDuration(Throwable error, java.time.Duration delay) {
+    recordActionableError(error);
+  }
+
+  @Override
+  public void attemptFailedRetriesExhausted(Throwable error) {
+    recordActionableError(error);
+  }
+
+  @Override
+  public void attemptPermanentFailure(Throwable error) {
+    recordActionableError(error);
+  }
+
+  private void recordActionableError(Throwable error) {
+    Map<String, Object> logContext = new HashMap<>();
+
+    if (apiTracerContext.rpcSystemName() != null) {
+      logContext.put(
+          ObservabilityAttributes.RPC_SYSTEM_NAME_ATTRIBUTE, apiTracerContext.rpcSystemName());
+    }
+    if (apiTracerContext.fullMethodName() != null) {
+      logContext.put(
+          ObservabilityAttributes.GRPC_RPC_METHOD_ATTRIBUTE, apiTracerContext.fullMethodName());
+    }
+    if (apiTracerContext.serverPort() != null) {
+      logContext.put(ObservabilityAttributes.SERVER_PORT_ATTRIBUTE, apiTracerContext.serverPort());
+    }
+    if (apiTracerContext.libraryMetadata() != null
+        && !apiTracerContext.libraryMetadata().isEmpty()) {
+      if (apiTracerContext.libraryMetadata().repository() != null) {
+        logContext.put(
+            ObservabilityAttributes.REPO_ATTRIBUTE,
+            apiTracerContext.libraryMetadata().repository());
+      }
+    }
+
+    if (error != null) {
+      logContext.put(
+          ObservabilityAttributes.RPC_RESPONSE_STATUS_ATTRIBUTE,
+          ObservabilityUtils.extractStatus(error));
+    }
+
+    if (error instanceof ApiException) {
+      ApiException apiException = (ApiException) error;
+      if (apiException.getErrorDetails() != null) {
+        ErrorInfo errorInfo = apiException.getErrorDetails().getErrorInfo();
+        if (errorInfo != null) {
+          logContext.put("error.type", errorInfo.getReason());
+          logContext.put("gcp.errors.domain", errorInfo.getDomain());
+          for (Map.Entry<String, String> entry : errorInfo.getMetadataMap().entrySet()) {
+            logContext.put("gcp.errors.metadata." + entry.getKey(), entry.getValue());
+          }
+        }
+      }
+    }
+
+    String message = "Unknown Error";
+    if (error != null) {
+      message = error.getMessage() != null ? error.getMessage() : error.getClass().getName();
+    }
+    LoggingUtils.logActionableError(logContext, LOGGER_PROVIDER, message);
+  }
+}

gax-java/gax/src/main/java/com/google/api/gax/tracing/LoggingTracerFactory.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.api.gax.tracing;
+
+import com.google.api.core.BetaApi;
+import com.google.api.core.InternalApi;
+
+/** A {@link ApiTracerFactory} that creates instances of {@link LoggingTracer}. */
+@BetaApi
+@InternalApi
+public class LoggingTracerFactory implements ApiTracerFactory {
+  private final ApiTracerContext apiTracerContext;
+
+  public LoggingTracerFactory() {
+    this(ApiTracerContext.empty());
+  }
+
+  private LoggingTracerFactory(ApiTracerContext apiTracerContext) {
+    this.apiTracerContext = apiTracerContext;
+  }
+
+  @Override
+  public ApiTracer newTracer(ApiTracer parent, SpanName spanName, OperationType operationType) {
+    return new LoggingTracer(apiTracerContext);
+  }
+
+  @Override
+  public ApiTracer newTracer(ApiTracer parent, ApiTracerContext context) {
+    return new LoggingTracer(context);
+  }
+
+  @Override
+  public ApiTracerContext getApiTracerContext() {
+    return apiTracerContext;
+  }
+
+  @Override
+  public ApiTracerFactory withContext(ApiTracerContext context) {
+    return new LoggingTracerFactory(apiTracerContext.merge(context));
+  }
+}

gax-java/gax/src/test/java/com/google/api/gax/logging/LoggingUtilsTest.java

@@ -33,11 +33,20 @@
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
 
 import com.google.api.gax.logging.LoggingUtils.ThrowingRunnable;
+import java.util.Collections;
+import java.util.Map;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
+import org.slf4j.Logger;
 
 class LoggingUtilsTest {
 
@@ -77,4 +86,37 @@ void testExecuteWithTryCatch_WithNoSuchMethodError() throws Throwable {
     // Verify that the action was executed (despite the error)
     verify(action).run();
   }
+
+  @AfterEach
+  void tearDown() {
+    LoggingUtils.setLoggingEnabled(false);
+  }
+
+  @Test
+  void testLogActionableError_loggingDisabled() {
+    LoggingUtils.setLoggingEnabled(false);
+    LoggerProvider loggerProvider = mock(LoggerProvider.class);
+
+    LoggingUtils.logActionableError(
+        Collections.<String, Object>emptyMap(), loggerProvider, "message");
+
+    verify(loggerProvider, never()).getLogger();
+  }
+
+  @Test
+  void testLogActionableError_success() {
+    LoggingUtils.setLoggingEnabled(true);
+    LoggerProvider loggerProvider = mock(LoggerProvider.class);
+    Logger logger = mock(Logger.class);
+    when(loggerProvider.getLogger()).thenReturn(logger);
+
+    org.slf4j.spi.LoggingEventBuilder eventBuilder = mock(org.slf4j.spi.LoggingEventBuilder.class);
+    when(logger.atDebug()).thenReturn(eventBuilder);
+    when(eventBuilder.addKeyValue(anyString(), any())).thenReturn(eventBuilder);
+
+    Map<String, Object> context = Collections.singletonMap("key", "value");
+    LoggingUtils.logActionableError(context, loggerProvider, "message");
+
+    verify(loggerProvider).getLogger();
+  }
 }

gax-java/gax/src/test/java/com/google/api/gax/tracing/LoggingTracerFactoryTest.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.api.gax.tracing;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class LoggingTracerFactoryTest {
+
+  @Test
+  void testNewTracer_CreatesLoggingTracer() {
+    LoggingTracerFactory factory = new LoggingTracerFactory();
+    ApiTracer tracer =
+        factory.newTracer(
+            BaseApiTracer.getInstance(),
+            SpanName.of("client", "method"),
+            ApiTracerFactory.OperationType.Unary);
+
+    assertNotNull(tracer);
+    assertTrue(tracer instanceof LoggingTracer);
+  }
+
+  @Test
+  void testNewTracer_WithContext_CreatesLoggingTracer() {
+    LoggingTracerFactory factory = new LoggingTracerFactory();
+    ApiTracer tracer = factory.newTracer(BaseApiTracer.getInstance(), ApiTracerContext.empty());
+
+    assertNotNull(tracer);
+    assertTrue(tracer instanceof LoggingTracer);
+  }
+
+  @Test
+  void testWithContext_ReturnsNewFactoryWithMergedContext() {
+    LoggingTracerFactory factory = new LoggingTracerFactory();
+    ApiTracerContext context = ApiTracerContext.newBuilder().setServerAddress("address").build();
+    ApiTracerFactory updatedFactory = factory.withContext(context);
+
+    assertNotNull(updatedFactory);
+    assertTrue(updatedFactory instanceof LoggingTracerFactory);
+    assertEquals("address", updatedFactory.getApiTracerContext().serverAddress());
+  }
+}