feat: MetricsTracer implementation (#2421)

* feat: Opentelemetry implementation

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

@@ -32,6 +32,16 @@
 
 import com.google.api.core.BetaApi;
 import com.google.api.core.InternalApi;
+import com.google.api.gax.rpc.ApiException;
+import com.google.api.gax.rpc.StatusCode;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Stopwatch;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.Nullable;
+import org.threeten.bp.Duration;
 
 /**
  * This class computes generic metrics that can be observed in the lifecycle of an RPC operation.
@@ -42,12 +52,173 @@
 @InternalApi
 public class MetricsTracer implements ApiTracer {
 
-  public MetricsTracer(MethodName methodName, MetricsRecorder metricsRecorder) {}
+  private static final String STATUS_ATTRIBUTE = "status";
+
+  private Stopwatch attemptTimer;
+
+  private final Stopwatch operationTimer = Stopwatch.createStarted();
+
+  private final Map<String, String> attributes = new HashMap<>();
+
+  private MetricsRecorder metricsRecorder;
+
+  public MetricsTracer(MethodName methodName, MetricsRecorder metricsRecorder) {
+    this.attributes.put("method_name", methodName.toString());
+    this.metricsRecorder = metricsRecorder;
+  }
+
+  /**
+   * Signals that the overall operation has finished successfully. The tracer is now considered
+   * closed and should no longer be used. Successful operation adds "OK" value to the status
+   * attribute key.
+   */
+  @Override
+  public void operationSucceeded() {
+    attributes.put(STATUS_ATTRIBUTE, StatusCode.Code.OK.toString());
+    metricsRecorder.recordOperationLatency(
+        operationTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordOperationCount(1, attributes);
+  }
+
+  /**
+   * Signals that the operation was cancelled by the user. The tracer is now considered closed and
+   * should no longer be used. Cancelled operation adds "CANCELLED" value to the status attribute
+   * key.
+   */
+  @Override
+  public void operationCancelled() {
+    attributes.put(STATUS_ATTRIBUTE, StatusCode.Code.CANCELLED.toString());
+    metricsRecorder.recordOperationLatency(
+        operationTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordOperationCount(1, attributes);
+  }
+
+  /**
+   * Signals that the operation was cancelled by the user. The tracer is now considered closed and
+   * should no longer be used. Failed operation extracts the error from the throwable and adds it to
+   * the status attribute key.
+   */
+  @Override
+  public void operationFailed(Throwable error) {
+    attributes.put(STATUS_ATTRIBUTE, extractStatus(error));
+    metricsRecorder.recordOperationLatency(
+        operationTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordOperationCount(1, attributes);
+  }
+
+  /**
+   * Adds an annotation that an attempt is about to start with additional information from the
+   * request. In general this should occur at the very start of the operation. The attemptNumber is
+   * zero based. So the initial attempt will be 0. When the attempt starts, the attemptTimer starts
+   * the stopwatch.
+   *
+   * @param attemptNumber the zero based sequential attempt number.
+   * @param request request of this attempt.
+   */
+  @Override
+  public void attemptStarted(Object request, int attemptNumber) {
+    attemptTimer = Stopwatch.createStarted();
+  }
+
+  /**
+   * Adds an annotation that the attempt succeeded. Successful attempt add "OK" value to the status
+   * attribute key.
+   */
+  @Override
+  public void attemptSucceeded() {
+
+    attributes.put(STATUS_ATTRIBUTE, StatusCode.Code.OK.toString());
+    metricsRecorder.recordAttemptLatency(attemptTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordAttemptCount(1, attributes);
+  }
+
+  /**
+   * Add an annotation that the attempt was cancelled by the user. Cancelled attempt add "CANCELLED"
+   * to the status attribute key.
+   */
+  @Override
+  public void attemptCancelled() {
+
+    attributes.put(STATUS_ATTRIBUTE, StatusCode.Code.CANCELLED.toString());
+    metricsRecorder.recordAttemptLatency(attemptTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordAttemptCount(1, attributes);
+  }
+
+  /**
+   * Adds an annotation that the attempt failed, but another attempt will be made after the delay.
+   *
+   * @param error the error that caused the attempt to fail.
+   * @param delay the amount of time to wait before the next attempt will start.
+   *     <p>Failed attempt extracts the error from the throwable and adds it to the status attribute
+   *     key.
+   */
+  @Override
+  public void attemptFailed(Throwable error, Duration delay) {
+
+    attributes.put(STATUS_ATTRIBUTE, extractStatus(error));
+    metricsRecorder.recordAttemptLatency(attemptTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordAttemptCount(1, attributes);
+  }
+
+  /**
+   * Adds an annotation that the attempt failed and that no further attempts will be made because
+   * retry limits have been reached. This extracts the error from the throwable and adds it to the
+   * status attribute key.
+   *
+   * @param error the last error received before retries were exhausted.
+   */
+  @Override
+  public void attemptFailedRetriesExhausted(Throwable error) {
+
+    attributes.put(STATUS_ATTRIBUTE, extractStatus(error));
+    metricsRecorder.recordAttemptLatency(attemptTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordAttemptCount(1, attributes);
+  }
+
+  /**
+   * Adds an annotation that the attempt failed and that no further attempts will be made because
+   * the last error was not retryable. This extracts the error from the throwable and adds it to the
+   * status attribute key.
+   *
+   * @param error the error that caused the final attempt to fail.
+   */
+  @Override
+  public void attemptPermanentFailure(Throwable error) {
+
+    attributes.put(STATUS_ATTRIBUTE, extractStatus(error));
+    metricsRecorder.recordAttemptLatency(attemptTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    metricsRecorder.recordAttemptCount(1, attributes);
+  }
+
+  /** Function to extract the status of the error as a string */
+  @VisibleForTesting
+  static String extractStatus(@Nullable Throwable error) {
+    final String statusString;
+
+    if (error == null) {
+      return StatusCode.Code.OK.toString();
+    } else if (error instanceof CancellationException) {
+      statusString = StatusCode.Code.CANCELLED.toString();
+    } else if (error instanceof ApiException) {
+      statusString = ((ApiException) error).getStatusCode().getCode().toString();
+    } else {
+      statusString = StatusCode.Code.UNKNOWN.toString();
+    }
+
+    return statusString;
+  }
 
   /**
    * Add attributes that will be attached to all metrics. This is expected to be called by
    * handwritten client teams to add additional attributes that are not supposed be collected by
    * Gax.
    */
-  public void addAttributes(String key, String value) {};
+  public void addAttributes(String key, String value) {
+    attributes.put(key, value);
+  };
+
+  @VisibleForTesting
+  Map<String, String> getAttributes() {
+    return attributes;
+  }
 }

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

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2024 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.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.google.api.gax.tracing.ApiTracerFactory.OperationType;
+import com.google.common.truth.Truth;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+
+public class MetricsTracerFactoryTest {
+  @Mock private MetricsRecorder metricsRecorder;
+  @Mock private ApiTracer parent;
+  private SpanName spanName;
+  private MetricsTracerFactory metricsTracerFactory;
+
+  @Before
+  public void setUp() {
+    // Create an instance of MetricsTracerFactory with the mocked MetricsRecorder
+    metricsTracerFactory = new MetricsTracerFactory(metricsRecorder);
+
+    spanName = mock(SpanName.class);
+    when(spanName.getClientName()).thenReturn("testService");
+    when(spanName.getMethodName()).thenReturn("testMethod");
+  }
+
+  @Test
+  public void testNewTracer_notNull() {
+    // Call the newTracer method
+    ApiTracer apiTracer = metricsTracerFactory.newTracer(parent, spanName, OperationType.Unary);
+
+    // Assert that the apiTracer created has expected type and not null
+    Truth.assertThat(apiTracer).isInstanceOf(MetricsTracer.class);
+    Truth.assertThat(apiTracer).isNotNull();
+  }
+
+  @Test
+  public void testNewTracer_HasCorrectParameters() {
+
+    // Call the newTracer method
+    ApiTracer apiTracer = metricsTracerFactory.newTracer(parent, spanName, OperationType.Unary);
+
+    // Assert that the apiTracer created has expected type and not null
+    Truth.assertThat(apiTracer).isInstanceOf(MetricsTracer.class);
+    Truth.assertThat(apiTracer).isNotNull();
+
+    MetricsTracer metricsTracer = (MetricsTracer) apiTracer;
+    Truth.assertThat(metricsTracer.getAttributes().get("method_name"))
+        .isEqualTo("testService.testMethod");
+  }
+}