chore: Add MetricsRecorder interface to Datastore

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/DatastoreImpl.java

@@ -16,14 +16,14 @@
 
 package com.google.cloud.datastore;
 
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_DEFERRED;
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_DOCUMENT_COUNT;
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_MISSING;
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_MORE_RESULTS;
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_READ_CONSISTENCY;
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_RECEIVED;
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_TRANSACTIONAL;
-import static com.google.cloud.datastore.telemetry.TraceUtil.ATTRIBUTES_KEY_TRANSACTION_ID;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_DEFERRED;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_DOCUMENT_COUNT;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_MISSING;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_MORE_RESULTS;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_READ_CONSISTENCY;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_RECEIVED;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_TRANSACTIONAL;
+import static com.google.cloud.datastore.telemetry.TelemetryConstants.ATTRIBUTES_KEY_TRANSACTION_ID;
 import static com.google.cloud.datastore.telemetry.TraceUtil.SPAN_NAME_ALLOCATE_IDS;
 import static com.google.cloud.datastore.telemetry.TraceUtil.SPAN_NAME_BEGIN_TRANSACTION;
 import static com.google.cloud.datastore.telemetry.TraceUtil.SPAN_NAME_COMMIT;

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/telemetry/MetricsRecorder.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.datastore.telemetry;
+
+import com.google.cloud.datastore.DatastoreOpenTelemetryOptions;
+import io.opentelemetry.api.GlobalOpenTelemetry;
+import io.opentelemetry.api.OpenTelemetry;
+import java.util.Map;
+import javax.annotation.Nonnull;
+
+/** Interface to record specific metric operations. */
+public interface MetricsRecorder {
+  /** Records the total latency of a transaction in milliseconds. */
+  void recordTransactionLatency(double latencyMs, Map<String, String> attributes);
+
+  /** Records the number of attempts a transaction took. */
+  void recordTransactionAttemptCount(long count, Map<String, String> attributes);
+
+  /**
+   * Returns a {@link MetricsRecorder} instance based on the provided OpenTelemetry options.
+   *
+   * @param options The {@link com.google.cloud.datastore.DatastoreOpenTelemetryOptions} configuring
+   *     telemetry.
+   * @return An {@link OpenTelemetryMetricsRecorder} if metrics are enabled, otherwise a {@link
+   *     NoOpMetricsRecorder}.
+   */
+  static MetricsRecorder getInstance(@Nonnull DatastoreOpenTelemetryOptions options) {
+    boolean isMetricsEnabled = options.isMetricsEnabled();
+
+    if (isMetricsEnabled) {
+      OpenTelemetry openTelemetry = options.getOpenTelemetry();
+      if (openTelemetry == null) {
+        return new OpenTelemetryMetricsRecorder(GlobalOpenTelemetry.get());
+      }
+      return new OpenTelemetryMetricsRecorder(openTelemetry);
+    } else {
+      return new NoOpMetricsRecorder();
+    }
+  }
+}

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/telemetry/NoOpMetricsRecorder.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.datastore.telemetry;
+
+import java.util.Map;
+
+/**
+ * Metrics recorder implementation, used to stub out metrics instrumentation when metrics are
+ * disabled.
+ */
+class NoOpMetricsRecorder implements MetricsRecorder {
+
+  @Override
+  public void recordTransactionLatency(double latencyMs, Map<String, String> attributes) {
+    /* No-Op OTel Operation */
+  }
+
+  @Override
+  public void recordTransactionAttemptCount(long count, Map<String, String> attributes) {
+    /* No-Op OTel Operation */
+  }
+}

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/telemetry/OpenTelemetryMetricsRecorder.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.datastore.telemetry;
+
+import io.opentelemetry.api.OpenTelemetry;
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.common.AttributesBuilder;
+import io.opentelemetry.api.metrics.DoubleHistogram;
+import io.opentelemetry.api.metrics.LongCounter;
+import io.opentelemetry.api.metrics.Meter;
+import java.util.Map;
+import javax.annotation.Nonnull;
+
+/**
+ * OpenTelemetry metrics recorder implementation, used to record metrics when metrics are enabled.
+ */
+class OpenTelemetryMetricsRecorder implements MetricsRecorder {
+  private final OpenTelemetry openTelemetry;
+
+  private final DoubleHistogram transactionLatency;
+  private final LongCounter transactionAttemptCount;
+
+  OpenTelemetryMetricsRecorder(@Nonnull OpenTelemetry openTelemetry) {
+    this.openTelemetry = openTelemetry;
+
+    Meter meter = openTelemetry.getMeter(TelemetryConstants.METER_NAME);
+
+    this.transactionLatency =
+        meter
+            .histogramBuilder(TelemetryConstants.SERVICE_NAME + "/transaction_latency")
+            .setDescription("Total latency for successful transaction operations")
+            .setUnit("ms")
+            .build();
+
+    this.transactionAttemptCount =
+        meter
+            .counterBuilder(TelemetryConstants.SERVICE_NAME + "/transaction_attempt_count")
+            .setDescription("Number of attempts to commit a transaction")
+            .build();
+  }
+
+  OpenTelemetry getOpenTelemetry() {
+    return openTelemetry;
+  }
+
+  @Override
+  public void recordTransactionLatency(double latencyMs, Map<String, String> attributes) {
+    transactionLatency.record(latencyMs, toOtelAttributes(attributes));
+  }
+
+  @Override
+  public void recordTransactionAttemptCount(long count, Map<String, String> attributes) {
+    transactionAttemptCount.add(count, toOtelAttributes(attributes));
+  }
+
+  private static Attributes toOtelAttributes(Map<String, String> attributes) {
+    AttributesBuilder builder = Attributes.builder();
+    if (attributes != null) {
+      attributes.forEach(builder::put);
+    }
+    return builder.build();
+  }
+}

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/telemetry/TelemetryConstants.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.datastore.telemetry;
+
+import com.google.api.core.InternalApi;
+
+/** Internal telemetry constants shared between OpenTelemetry tracing and metrics. */
+@InternalApi
+public class TelemetryConstants {
+  static final String SERVICE_NAME = "datastore.googleapis.com";
+  static final String METER_NAME = "com.google.cloud.datastore";
+
+  public static final String ATTRIBUTES_KEY_DOCUMENT_COUNT = "doc_count";
+  public static final String ATTRIBUTES_KEY_TRANSACTIONAL = "transactional";
+  public static final String ATTRIBUTES_KEY_TRANSACTION_ID = "transaction_id";
+  public static final String ATTRIBUTES_KEY_READ_CONSISTENCY = "read_consistency";
+  public static final String ATTRIBUTES_KEY_RECEIVED = "Received";
+  public static final String ATTRIBUTES_KEY_MISSING = "Missing";
+  public static final String ATTRIBUTES_KEY_DEFERRED = "Deferred";
+  public static final String ATTRIBUTES_KEY_MORE_RESULTS = "more_results";
+
+  /* TODO(lawrenceqiu): For now, these are a duplicate of method names in TraceUtil. Those will use these eventually */
+  public static final String METHOD_ALLOCATE_IDS = "AllocateIds";
+  public static final String METHOD_BEGIN_TRANSACTION = "Transaction.Begin";
+  public static final String METHOD_COMMIT = "Commit";
+  public static final String METHOD_LOOKUP = "Lookup";
+  public static final String METHOD_RESERVE_IDS = "ReserveIds";
+  public static final String METHOD_RUN_QUERY = "RunQuery";
+  public static final String METHOD_TRANSACTION_COMMIT = "Transaction.Commit";
+  public static final String METHOD_TRANSACTION_LOOKUP = "Transaction.Lookup";
+  public static final String METHOD_TRANSACTION_RUN = "Transaction.Run";
+  public static final String METHOD_TRANSACTION_RUN_QUERY = "Transaction.RunQuery";
+  public static final String METHOD_TRANSACTION_ROLLBACK = "Transaction.Rollback";
+  public static final String METHOD_TRANSACTION_RUN_AGGREGATION_QUERY =
+      "Transaction.RunAggregationQuery";
+  public static final String METHOD_ADD = "add";
+  public static final String METHOD_PUT = "put";
+  public static final String METHOD_UPDATE = "update";
+  public static final String METHOD_DELETE = "delete";
+  public static final String METHOD_SUBMIT = "submit";
+
+  private TelemetryConstants() {}
+}

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/telemetry/TraceUtil.java

@@ -46,14 +46,6 @@ public interface TraceUtil {
   String SPAN_NAME_TRANSACTION_RUN_QUERY = "Transaction.RunQuery";
   String SPAN_NAME_ROLLBACK = "Transaction.Rollback";
   String SPAN_NAME_TRANSACTION_RUN_AGGREGATION_QUERY = "Transaction.RunAggregationQuery";
-  String ATTRIBUTES_KEY_DOCUMENT_COUNT = "doc_count";
-  String ATTRIBUTES_KEY_TRANSACTIONAL = "transactional";
-  String ATTRIBUTES_KEY_TRANSACTION_ID = "transaction_id";
-  String ATTRIBUTES_KEY_READ_CONSISTENCY = "read_consistency";
-  String ATTRIBUTES_KEY_RECEIVED = "Received";
-  String ATTRIBUTES_KEY_MISSING = "Missing";
-  String ATTRIBUTES_KEY_DEFERRED = "Deferred";
-  String ATTRIBUTES_KEY_MORE_RESULTS = "more_results";
 
   /**
    * Creates and returns an instance of the TraceUtil class.