chore: preserve default TLS authority for bypass-routed channels (#4396)

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

Author: 2 people

java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/GrpcChannelEndpointCache.java

@@ -19,14 +19,17 @@
 import com.google.api.core.InternalApi;
 import com.google.api.gax.grpc.GrpcTransportChannel;
 import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
+import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider.Builder;
 import com.google.api.gax.rpc.TransportChannelProvider;
 import com.google.cloud.spanner.ErrorCode;
 import com.google.cloud.spanner.SpannerExceptionFactory;
 import com.google.common.annotations.VisibleForTesting;
 import io.grpc.ConnectivityState;
 import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
 import java.io.IOException;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -47,6 +50,7 @@ class GrpcChannelEndpointCache implements ChannelEndpointCache {
   private final InstantiatingGrpcChannelProvider baseProvider;
   private final Map<String, GrpcChannelEndpoint> servers = new ConcurrentHashMap<>();
   private final GrpcChannelEndpoint defaultEndpoint;
+  private final String defaultAuthority;
   private final AtomicBoolean isShutdown = new AtomicBoolean(false);
 
   /**
@@ -61,6 +65,7 @@ public GrpcChannelEndpointCache(InstantiatingGrpcChannelProvider channelProvider
     this.baseProvider = channelProvider;
     String defaultEndpoint = channelProvider.getEndpoint();
     this.defaultEndpoint = new GrpcChannelEndpoint(defaultEndpoint, channelProvider);
+    this.defaultAuthority = this.defaultEndpoint.getChannel().authority();
     this.servers.put(defaultEndpoint, this.defaultEndpoint);
   }
 
@@ -82,7 +87,7 @@ public ChannelEndpoint get(String address) {
           try {
             // Create a new provider with the same config but different endpoint.
             // This is thread-safe as withEndpoint() returns a new provider instance.
-            TransportChannelProvider newProvider = baseProvider.withEndpoint(addr);
+            TransportChannelProvider newProvider = createProviderWithAuthorityOverride(addr);
             return new GrpcChannelEndpoint(addr, newProvider);
           } catch (IOException e) {
             throw SpannerExceptionFactory.newSpannerException(
@@ -91,6 +96,26 @@ public ChannelEndpoint get(String address) {
         });
   }
 
+  private TransportChannelProvider createProviderWithAuthorityOverride(String address) {
+    InstantiatingGrpcChannelProvider endpointProvider =
+        (InstantiatingGrpcChannelProvider) baseProvider.withEndpoint(address);
+    if (Objects.equals(defaultAuthority, address)) {
+      return endpointProvider;
+    }
+    Builder builder = endpointProvider.toBuilder();
+    final com.google.api.core.ApiFunction<ManagedChannelBuilder, ManagedChannelBuilder>
+        baseConfigurator = builder.getChannelConfigurator();
+    builder.setChannelConfigurator(
+        channelBuilder -> {
+          ManagedChannelBuilder effectiveBuilder = channelBuilder;
+          if (baseConfigurator != null) {
+            effectiveBuilder = baseConfigurator.apply(effectiveBuilder);
+          }
+          return effectiveBuilder.overrideAuthority(defaultAuthority);
+        });
+    return builder.build();
+  }
+
   @Override
   public void evict(String address) {
     if (defaultEndpoint.getAddress().equals(address)) {

java-spanner/google-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/GrpcChannelEndpointCacheTest.java

@@ -60,6 +60,18 @@ public void getCachesPerAddress() throws Exception {
     }
   }
 
+  @Test
+  public void routedChannelsReuseDefaultAuthority() throws Exception {
+    GrpcChannelEndpointCache cache = new GrpcChannelEndpointCache(createProvider("localhost:1234"));
+    try {
+      ChannelEndpoint routed = cache.get("localhost:1111");
+
+      assertThat(routed.getChannel().authority()).isEqualTo("localhost:1234");
+    } finally {
+      cache.shutdown();
+    }
+  }
+
   @Test
   public void evictRemovesNonDefaultServer() throws Exception {
     GrpcChannelEndpointCache cache = new GrpcChannelEndpointCache(createProvider("localhost:1234"));