Demonstrate implementing couple OpenTelemetry metrics in the core Java

library.

google-cloud-bigquerystorage/pom.xml

@@ -156,6 +156,10 @@
     <artifactId>google-auth-library-credentials</artifactId>
     <version>1.23.0</version>
   </dependency>
+    <dependency>
+      <groupId>io.opentelemetry</groupId>
+      <artifactId>opentelemetry-api</artifactId>
+    </dependency>
 
     <!-- Test dependencies -->
     <dependency>

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/ConnectionWorker.java

@@ -36,6 +36,11 @@
 import io.grpc.Status;
 import io.grpc.Status.Code;
 import io.grpc.StatusRuntimeException;
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.common.AttributesBuilder;
+import io.opentelemetry.api.metrics.LongCounter;
+import io.opentelemetry.api.metrics.Meter;
+import io.opentelemetry.api.metrics.MeterProvider;
 import java.io.IOException;
 import java.time.Duration;
 import java.time.Instant;
@@ -250,6 +255,11 @@ class ConnectionWorker implements AutoCloseable {
   private static String projectMatching = "projects/[^/]+/";
   private static Pattern streamPatternProject = Pattern.compile(projectMatching);
 
+  private Meter writeMeter;
+  private final Attributes telemetryAttributes;
+  private LongCounter instrumentIncomingRequestCount;
+  private LongCounter instrumentIncomingRequestSize;
+
   static final Pattern DEFAULT_STREAM_PATTERN =
       Pattern.compile("projects/([^/]+)/datasets/([^/]+)/tables/([^/]+)/(streams/)?_default$");
 
@@ -278,6 +288,70 @@ static String getRoutingHeader(String streamName, String location) {
     return project + "locations/" + location;
   }
 
+  private Attributes buildOpenTelemetryAttributes() {
+    AttributesBuilder builder = Attributes.builder().put("writerId", this.writerId);
+    builder.put("streamId", this.streamName);
+    if (!this.traceId.isEmpty()) {
+      String[] traceIdParts = this.traceId.split(":", 5);
+      for (int i = 0; i < traceIdParts.length; i++) {
+        builder.put("traceField" + i, traceIdParts[i]);
+      }
+    }
+    return builder.build();
+  }
+
+  private void registerOpenTelemetryMetrics() {
+    MeterProvider meterProvider = Singletons.getOpenTelemetry().getMeterProvider();
+    writeMeter =
+        meterProvider
+            .meterBuilder("com.google.cloud.bigquery.storage.v1.write")
+            .setInstrumentationVersion(
+                ConnectionWorker.class.getPackage().getImplementationVersion())
+            .build();
+    instrumentIncomingRequestCount =
+        writeMeter
+            .counterBuilder("incoming-request-count")
+            .setDescription("Counts number of incoming requests")
+            .build();
+    instrumentIncomingRequestSize =
+        writeMeter
+            .counterBuilder("incoming-request-size")
+            .setDescription("Counts byte size of incoming requests")
+            .build();
+    writeMeter
+        .gaugeBuilder("waiting-queue-length")
+        .ofLongs()
+        .setDescription(
+            "Reports length of waiting queue. This queue contains requests buffered in the client and not yet sent to the server.")
+        .buildWithCallback(
+            result -> {
+              long waitQueueSize = 0;
+              this.lock.lock();
+              try {
+                waitQueueSize = this.waitingRequestQueue.size();
+              } finally {
+                this.lock.unlock();
+              }
+              result.record(waitQueueSize, telemetryAttributes);
+            });
+    writeMeter
+        .gaugeBuilder("inflight-queue-length")
+        .ofLongs()
+        .setDescription(
+            "Reports length of inflight queue. This queue contains sent append requests waiting for response from server.")
+        .buildWithCallback(
+            result -> {
+              long inflightQueueSize = 0;
+              this.lock.lock();
+              try {
+                inflightQueueSize = this.inflightRequestQueue.size();
+              } finally {
+                this.lock.unlock();
+              }
+              result.record(inflightQueueSize, telemetryAttributes);
+            });
+  }
+
   public ConnectionWorker(
       String streamName,
       String location,
@@ -312,6 +386,9 @@ public ConnectionWorker(
     this.inflightRequestQueue = new LinkedList<AppendRequestAndResponse>();
     this.compressorName = compressorName;
     this.retrySettings = retrySettings;
+    this.telemetryAttributes = buildOpenTelemetryAttributes();
+    registerOpenTelemetryMetrics();
+
     // Always recreate a client for connection worker.
     HashMap<String, String> newHeaders = new HashMap<>();
     newHeaders.putAll(clientSettings.toBuilder().getHeaderProvider().getHeaders());
@@ -506,6 +583,8 @@ private ApiFuture<AppendRowsResponse> appendInternal(
                           + requestWrapper.messageSize)));
       return requestWrapper.appendResult;
     }
+    instrumentIncomingRequestCount.add(1, telemetryAttributes);
+    instrumentIncomingRequestSize.add(requestWrapper.messageSize, telemetryAttributes);
     this.lock.lock();
     try {
       if (userClosed) {

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/Singletons.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2024 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
+ *
+ *     https://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.bigquery.storage.v1;
+
+import io.opentelemetry.api.GlobalOpenTelemetry;
+import io.opentelemetry.api.OpenTelemetry;
+import java.util.logging.Logger;
+
+/** Container for global singleton objects. */
+class Singletons {
+
+  private static final Logger log = Logger.getLogger(Singletons.class.getName());
+
+  // Global OpenTelemetry instance
+  private static OpenTelemetry openTelemetry = null;
+
+  static OpenTelemetry getOpenTelemetry() {
+    if (openTelemetry == null) {
+      openTelemetry = GlobalOpenTelemetry.get();
+    }
+    return openTelemetry;
+  }
+}

pom.xml

@@ -120,7 +120,13 @@
         <artifactId>json</artifactId>
         <version>20240303</version>
       </dependency>
-
+      <dependency>
+        <groupId>io.opentelemetry</groupId>
+        <artifactId>opentelemetry-bom</artifactId>
+        <version>1.38.0</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
 
       <!-- Test dependencies -->
       <dependency>