PoC: Otel metrics

gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/ChannelPool.java

@@ -30,6 +30,7 @@
 package com.google.api.gax.grpc;
 
 import com.google.api.core.InternalApi;
+import com.google.api.gax.tracing.ClientMetricsTracer;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
@@ -80,11 +81,22 @@ class ChannelPool extends ManagedChannel {
   private final AtomicInteger indexTicker = new AtomicInteger();
   private final String authority;
 
+  private ClientMetricsTracer clientMetricsTracer;
   static ChannelPool create(ChannelPoolSettings settings, ChannelFactory channelFactory)
-      throws IOException {
+          throws IOException {
     return new ChannelPool(settings, channelFactory, Executors.newSingleThreadScheduledExecutor());
   }
 
+  static ChannelPool create(ChannelPoolSettings settings, ChannelFactory channelFactory, ClientMetricsTracer clientMetricsTracer)
+      throws IOException {
+    ChannelPool channelPool = new ChannelPool(settings, channelFactory, Executors.newSingleThreadScheduledExecutor());
+    channelPool.clientMetricsTracer = clientMetricsTracer;
+    if (channelPool.clientMetricsTracer != null) {
+      channelPool.clientMetricsTracer.recordCurrentChannelSize(1);
+    }
+    return channelPool;
+  }
+
   /**
    * Initializes the channel pool. Assumes that all channels have the same authority.
    *
@@ -298,6 +310,7 @@ void resize() {
 
       shrink(dampenedTarget);
     }
+    clientMetricsTracer.recordCurrentChannelSize(localEntries.size());
   }
 
   /** Not threadsafe, must be called under the entryWriteLock monitor */

gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/InstantiatingGrpcChannelProvider.java

@@ -40,6 +40,7 @@
 import com.google.api.gax.rpc.TransportChannelProvider;
 import com.google.api.gax.rpc.internal.EnvironmentProvider;
 import com.google.api.gax.rpc.mtls.MtlsProvider;
+import com.google.api.gax.tracing.ClientMetricsTracer;
 import com.google.auth.Credentials;
 import com.google.auth.oauth2.ComputeEngineCredentials;
 import com.google.common.annotations.VisibleForTesting;
@@ -112,7 +113,7 @@ public final class InstantiatingGrpcChannelProvider implements TransportChannelP
   @Nullable private final Boolean allowNonDefaultServiceAccount;
   @VisibleForTesting final ImmutableMap<String, ?> directPathServiceConfig;
   @Nullable private final MtlsProvider mtlsProvider;
-
+  @Nullable private ClientMetricsTracer clientMetricsTracer;
   @Nullable
   private final ApiFunction<ManagedChannelBuilder, ManagedChannelBuilder> channelConfigurator;
 
@@ -178,6 +179,11 @@ public String getTransportName() {
     return GrpcTransportChannel.getGrpcTransportName();
   }
 
+  @Override
+  public void setClientMetricsTracer(ClientMetricsTracer clientMetricsTracer) {
+    this.clientMetricsTracer = clientMetricsTracer;
+  }
+
   @Override
   public boolean needsEndpoint() {
     return endpoint == null;
@@ -235,7 +241,7 @@ public TransportChannel getTransportChannel() throws IOException {
   private TransportChannel createChannel() throws IOException {
     return GrpcTransportChannel.create(
         ChannelPool.create(
-            channelPoolSettings, InstantiatingGrpcChannelProvider.this::createSingleChannel));
+            channelPoolSettings, InstantiatingGrpcChannelProvider.this::createSingleChannel, clientMetricsTracer));
   }
 
   private boolean isDirectPathEnabled() {

gax-java/gax/pom.xml

@@ -57,6 +57,18 @@
       <artifactId>graal-sdk</artifactId>
       <scope>provided</scope>
     </dependency>
+    <dependency>
+      <groupId>io.opentelemetry</groupId>
+      <artifactId>opentelemetry-api</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>io.opentelemetry</groupId>
+      <artifactId>opentelemetry-sdk</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>io.opentelemetry</groupId>
+      <artifactId>opentelemetry-exporter-otlp</artifactId>
+    </dependency>
   </dependencies>
 
   <build>

gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientContext.java

@@ -39,6 +39,7 @@
 import com.google.api.gax.rpc.mtls.MtlsProvider;
 import com.google.api.gax.tracing.ApiTracerFactory;
 import com.google.api.gax.tracing.BaseApiTracerFactory;
+import com.google.api.gax.tracing.ClientMetricsTracer;
 import com.google.auth.Credentials;
 import com.google.auto.value.AutoValue;
 import com.google.common.collect.ImmutableList;
@@ -198,6 +199,9 @@ public static ClientContext create(StubSettings settings) throws IOException {
     if (transportChannelProvider.needsEndpoint()) {
       transportChannelProvider = transportChannelProvider.withEndpoint(endpoint);
     }
+    ClientMetricsTracer clientMetricsTracer = settings.getTracerFactory().newClientMetricsTracer();
+    transportChannelProvider.setClientMetricsTracer(clientMetricsTracer);
+
     TransportChannel transportChannel = transportChannelProvider.getTransportChannel();
 
     ApiCallContext defaultCallContext =

gax-java/gax/src/main/java/com/google/api/gax/rpc/TransportChannelProvider.java

@@ -31,6 +31,7 @@
 
 import com.google.api.core.BetaApi;
 import com.google.api.core.InternalExtensionOnly;
+import com.google.api.gax.tracing.ClientMetricsTracer;
 import com.google.auth.Credentials;
 import java.io.IOException;
 import java.util.Map;
@@ -142,4 +143,6 @@ public interface TransportChannelProvider {
    * <p>This string can be used for identifying transports for switching logic.
    */
   String getTransportName();
+
+  default void setClientMetricsTracer(ClientMetricsTracer clientMetricsTracer) {};
 }

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

@@ -101,6 +101,11 @@ public interface ApiTracer {
   /** Adds an annotation that the attempt succeeded. */
   void attemptSucceeded();
 
+  //This is for libraries to override to intended name
+  default String attemptLatencyName() {
+    return "attempt_latency";
+  };
+
   /** Add an annotation that the attempt was cancelled by the user. */
   void attemptCancelled();
 

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

@@ -61,4 +61,9 @@ enum OperationType {
    * @param operationType the type of operation that the tracer will trace
    */
   ApiTracer newTracer(ApiTracer parent, SpanName spanName, OperationType operationType);
+
+  //This probably needs to be moved to a new factory
+  default ClientMetricsTracer newClientMetricsTracer() {
+    return null;
+  };
 }

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

@@ -0,0 +1,10 @@
+package com.google.api.gax.tracing;
+
+public interface ClientMetricsTracer {
+
+    void recordCurrentChannelSize(int channelSize);
+
+    default String channelSizeName() {
+        return "channel_size";
+    };
+}

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

@@ -0,0 +1,21 @@
+package com.google.api.gax.tracing;
+
+import io.opentelemetry.api.metrics.Meter;
+
+public class OpenTelemetryClientMetricsTracer implements ClientMetricsTracer {
+
+    private Meter meter;
+    public OpenTelemetryClientMetricsTracer(Meter meter) {
+        this.meter = meter;
+    }
+
+    @Override
+    public void recordCurrentChannelSize(int channelSize) {
+        meter
+                .gaugeBuilder(channelSizeName())
+                .setDescription("Channel Size")
+                .setUnit("1")
+                .ofLongs()
+                .buildWithCallback(measurement -> measurement.record(channelSize));
+    }
+}

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

@@ -0,0 +1,150 @@
+/*
+ * Copyright 2023 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.common.base.Stopwatch;
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.metrics.DoubleHistogram;
+import io.opentelemetry.api.metrics.LongCounter;
+import io.opentelemetry.api.metrics.Meter;
+import org.threeten.bp.Duration;
+
+import java.util.concurrent.TimeUnit;
+
+import static io.opentelemetry.api.common.AttributeKey.stringKey;
+
+public class OpenTelemetryMetricsTracer implements ApiTracer {
+    protected Meter meter;
+
+    private Stopwatch attemptTimer;
+
+    private SpanName spanName;
+
+    public OpenTelemetryMetricsTracer(Meter meter, SpanName spanName) {
+        this.meter = meter;
+        this.spanName = spanName;
+    }
+
+    @Override
+    public Scope inScope() {
+        return () -> {};
+    }
+
+    @Override
+    public void operationSucceeded() {
+
+    }
+
+    @Override
+    public void operationCancelled() {
+
+    }
+
+    @Override
+    public void operationFailed(Throwable error) {
+
+    }
+
+    @Override
+    public void connectionSelected(String id) {
+
+    }
+
+    @Override
+    public void attemptStarted(int attemptNumber) {
+
+    }
+
+    @Override
+    public void attemptStarted(Object request, int attemptNumber) {
+        attemptTimer = Stopwatch.createStarted();
+        LongCounter longCounter = meter.counterBuilder("attempt_count")
+                .setDescription("Attempt Count")
+                .setUnit("1")
+                .build();
+        longCounter.add(1);
+    }
+
+    @Override
+    public void attemptSucceeded() {
+        DoubleHistogram doubleHistogram = meter.histogramBuilder(attemptLatencyName())
+                .setDescription("Duration of an individual operation attempt")
+                .setUnit("ms")
+                .build();
+        Attributes attributes = Attributes.of(stringKey("method_name"), spanName.toString());
+        doubleHistogram.record(attemptTimer.elapsed(TimeUnit.MILLISECONDS), attributes);
+    }
+
+    @Override
+    public void attemptCancelled() {
+
+    }
+
+    @Override
+    public void attemptFailed(Throwable error, Duration delay) {
+
+    }
+
+    @Override
+    public void attemptFailedRetriesExhausted(Throwable error) {
+
+    }
+
+    @Override
+    public void attemptPermanentFailure(Throwable error) {
+
+    }
+
+    @Override
+    public void lroStartFailed(Throwable error) {
+
+    }
+
+    @Override
+    public void lroStartSucceeded() {
+
+    }
+
+    @Override
+    public void responseReceived() {
+
+    }
+
+    @Override
+    public void requestSent() {
+
+    }
+
+    @Override
+    public void batchRequestSent(long elementCount, long requestSize) {
+
+    }
+}