no-op channel primer changes

Change-Id: I9ad5eeaacb02ace9ba3cf7c09b6846dcbc298fb8

Author: nicholsl

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/NoOpChannelPrimer.java

@@ -16,7 +16,9 @@
 package com.google.cloud.bigtable.data.v2.stub;
 
 import com.google.api.core.InternalApi;
-import com.google.api.gax.grpc.ChannelPrimer;
+import com.google.api.core.SettableApiFuture;
+import com.google.bigtable.v2.PingAndWarmResponse;
+import com.google.cloud.bigtable.gaxx.grpc.ChannelPrimer;
 import io.grpc.ManagedChannel;
 
 @InternalApi
@@ -31,4 +33,9 @@ private NoOpChannelPrimer() {}
   public void primeChannel(ManagedChannel managedChannel) {
     // No op
   }
+
+  @Override
+  public SettableApiFuture<PingAndWarmResponse> sendPrimeRequestsAsync(ManagedChannel var1) {
+    return null;
+  }
 }

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/gaxx/grpc/ChannelPoolHealthChecker.java

@@ -67,7 +67,7 @@ static ProbeResult create(Instant startTime, boolean success) {
   }
 
   private final Supplier<ImmutableList<Entry>> entrySupplier;
-  private Instant lastEviction;
+  private volatile Instant lastEviction;
   private ScheduledExecutorService executor;
 
   private ChannelPrimer channelPrimer;
@@ -112,7 +112,6 @@ public void stop() {
   /** Runs probes on all the channels in the pool. */
   @VisibleForTesting
   void runProbes() {
-    // Method stub, no operation.
     for (Entry entry : this.entrySupplier.get()) {
       Instant startTime = clock.instant();
       SettableApiFuture<PingAndWarmResponse> probeFuture =

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/gaxx/grpc/ChannelPrimer.java

@@ -1,3 +1,18 @@
+/*
+ * Copyright 2025 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.bigtable.gaxx.grpc;
 
 import com.google.api.core.InternalApi;