alts: convert handshaker service channel to SharedResourceHolder (#4802)

alts: convert handshaker service channel to SharedResourceHolder

alts/src/main/java/io/grpc/alts/AltsChannelBuilder.java

@@ -37,7 +37,9 @@ import io.grpc.alts.internal.RpcProtocolVersionsUtil;
 import io.grpc.alts.internal.TsiHandshaker;
 import io.grpc.alts.internal.TsiHandshakerFactory;
 import io.grpc.internal.GrpcUtil;
+import io.grpc.internal.ObjectPool;
 import io.grpc.internal.ProxyParameters;
+import io.grpc.internal.SharedResourcePool;
 import io.grpc.netty.InternalNettyChannelBuilder;
 import io.grpc.netty.InternalNettyChannelBuilder.TransportCreationParamsFilter;
 import io.grpc.netty.InternalNettyChannelBuilder.TransportCreationParamsFilterFactory;
@@ -60,6 +62,8 @@ public final class AltsChannelBuilder extends ForwardingChannelBuilder<AltsChann
   private final NettyChannelBuilder delegate;
   private final AltsClientOptions.Builder handshakerOptionsBuilder =
       new AltsClientOptions.Builder();
+  private ObjectPool<ManagedChannel> handshakerChannelPool =
+      SharedResourcePool.forResource(HandshakerServiceChannel.SHARED_HANDSHAKER_CHANNEL);
   private TcpfFactory tcpfFactoryForTest;
   private boolean enableUntrustedAlts;
 
@@ -109,7 +113,10 @@ public final class AltsChannelBuilder extends ForwardingChannelBuilder<AltsChann
 
   /** Sets a new handshaker service address for testing. */
   public AltsChannelBuilder setHandshakerAddressForTesting(String handshakerAddress) {
-    HandshakerServiceChannel.setHandshakerAddressForTesting(handshakerAddress);
+    // Instead of using the default shared channel to the handshaker service, create a fix object
+    // pool of handshaker service channel for testing.
+    handshakerChannelPool =
+        HandshakerServiceChannel.getHandshakerChannelPoolForTesting(handshakerAddress);
     return this;
   }
 
@@ -164,9 +171,11 @@ public final class AltsChannelBuilder extends ForwardingChannelBuilder<AltsChann
           @Override
           public TsiHandshaker newHandshaker() {
             // Used the shared grpc channel to connecting to the ALTS handshaker service.
-            ManagedChannel channel = HandshakerServiceChannel.get();
+            // TODO: Release the channel if it is not used.
+            // https://github.com/grpc/grpc-java/issues/4755.
             return AltsTsiHandshaker.newClient(
-                HandshakerServiceGrpc.newStub(channel), handshakerOptions);
+                HandshakerServiceGrpc.newStub(handshakerChannelPool.getObject()),
+                handshakerOptions);
           }
         };
 

alts/src/main/java/io/grpc/alts/AltsServerBuilder.java

@@ -21,6 +21,7 @@ import io.grpc.CompressorRegistry;
 import io.grpc.DecompressorRegistry;
 import io.grpc.ExperimentalApi;
 import io.grpc.HandlerRegistry;
+import io.grpc.ManagedChannel;
 import io.grpc.Metadata;
 import io.grpc.Server;
 import io.grpc.ServerBuilder;
@@ -39,6 +40,8 @@ import io.grpc.alts.internal.HandshakerServiceGrpc;
 import io.grpc.alts.internal.RpcProtocolVersionsUtil;
 import io.grpc.alts.internal.TsiHandshaker;
 import io.grpc.alts.internal.TsiHandshakerFactory;
+import io.grpc.internal.ObjectPool;
+import io.grpc.internal.SharedResourcePool;
 import io.grpc.netty.NettyServerBuilder;
 import java.io.File;
 import java.net.InetSocketAddress;
@@ -56,6 +59,8 @@ public final class AltsServerBuilder extends ServerBuilder<AltsServerBuilder> {
 
   private static final Logger logger = Logger.getLogger(AltsServerBuilder.class.getName());
   private final NettyServerBuilder delegate;
+  private ObjectPool<ManagedChannel> handshakerChannelPool =
+      SharedResourcePool.forResource(HandshakerServiceChannel.SHARED_HANDSHAKER_CHANNEL);
   private boolean enableUntrustedAlts;
 
   private AltsServerBuilder(NettyServerBuilder nettyDelegate) {
@@ -85,7 +90,10 @@ public final class AltsServerBuilder extends ServerBuilder<AltsServerBuilder> {
 
   /** Sets a new handshaker service address for testing. */
   public AltsServerBuilder setHandshakerAddressForTesting(String handshakerAddress) {
-    HandshakerServiceChannel.setHandshakerAddressForTesting(handshakerAddress);
+    // Instead of using the default shared channel to the handshaker service, create a fix object
+    // pool of handshaker service channel for testing.
+    handshakerChannelPool =
+        HandshakerServiceChannel.getHandshakerChannelPoolForTesting(handshakerAddress);
     return this;
   }
 
@@ -194,8 +202,10 @@ public final class AltsServerBuilder extends ServerBuilder<AltsServerBuilder> {
               @Override
               public TsiHandshaker newHandshaker() {
                 // Used the shared grpc channel to connecting to the ALTS handshaker service.
+                // TODO: Release the channel if it is not used.
+                // https://github.com/grpc/grpc-java/issues/4755.
                 return AltsTsiHandshaker.newServer(
-                    HandshakerServiceGrpc.newStub(HandshakerServiceChannel.get()),
+                    HandshakerServiceGrpc.newStub(handshakerChannelPool.getObject()),
                     new AltsHandshakerOptions(RpcProtocolVersionsUtil.getRpcProtocolVersions()));
               }
             }));

alts/src/main/java/io/grpc/alts/GoogleDefaultChannelBuilder.java

@@ -40,6 +40,7 @@ import io.grpc.alts.internal.TsiHandshakerFactory;
 import io.grpc.auth.MoreCallCredentials;
 import io.grpc.internal.GrpcUtil;
 import io.grpc.internal.ProxyParameters;
+import io.grpc.internal.SharedResourceHolder;
 import io.grpc.netty.GrpcSslContexts;
 import io.grpc.netty.InternalNettyChannelBuilder;
 import io.grpc.netty.InternalNettyChannelBuilder.TransportCreationParamsFilter;
@@ -115,7 +116,10 @@ public final class GoogleDefaultChannelBuilder
           @Override
           public TsiHandshaker newHandshaker() {
             // Used the shared grpc channel to connecting to the ALTS handshaker service.
-            ManagedChannel channel = HandshakerServiceChannel.get();
+            // TODO: Release the channel if it is not used.
+            // https://github.com/grpc/grpc-java/issues/4755.
+            ManagedChannel channel =
+                SharedResourceHolder.get(HandshakerServiceChannel.SHARED_HANDSHAKER_CHANNEL);
             return AltsTsiHandshaker.newClient(
                 HandshakerServiceGrpc.newStub(channel), handshakerOptions);
           }

alts/src/main/java/io/grpc/alts/HandshakerServiceChannel.java

@@ -16,43 +16,58 @@
 
 package io.grpc.alts;
 
-import com.google.common.base.Preconditions;
 import io.grpc.ManagedChannel;
+import io.grpc.internal.FixedObjectPool;
+import io.grpc.internal.SharedResourceHolder.Resource;
 import io.grpc.netty.NettyChannelBuilder;
+import io.netty.channel.EventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.util.concurrent.DefaultThreadFactory;
 import java.util.concurrent.ThreadFactory;
 
 /**
- * Class for creating a single shared grpc channel to the ALTS Handshaker Service. The channel to
- * the handshaker service is local and is over plaintext. Each application will have at most one
- * connection to the handshaker service.
- *
- * <p>TODO: Release the channel if it is not used. https://github.com/grpc/grpc-java/issues/4755.
+ * Class for creating a single shared gRPC channel to the ALTS Handshaker Service using
+ * SharedResourceHolder. The channel to the handshaker service is local and is over plaintext. Each
+ * application will have at most one connection to the handshaker service.
  */
 final class HandshakerServiceChannel {
-  // Default handshaker service address.
-  private static String handshakerAddress = "metadata.google.internal:8080";
-  // Shared channel to ALTS handshaker service.
-  private static ManagedChannel channel = null;
 
-  // Construct me not!
-  private HandshakerServiceChannel() {}
+  static final Resource<ManagedChannel> SHARED_HANDSHAKER_CHANNEL =
+      new Resource<ManagedChannel>() {
 
-  // Sets handshaker service address for testing and creates the channel to the handshaker service.
-  public static synchronized void setHandshakerAddressForTesting(String handshakerAddress) {
-    Preconditions.checkState(
-        channel == null || HandshakerServiceChannel.handshakerAddress.equals(handshakerAddress),
-        "HandshakerServiceChannel already created with a different handshakerAddress");
-    HandshakerServiceChannel.handshakerAddress = handshakerAddress;
-    if (channel == null) {
-      channel = createChannel();
-    }
-  }
+        private EventLoopGroup eventGroup = null;
 
-  /** Create a new channel to ALTS handshaker service, if it has not been created yet. */
-  private static ManagedChannel createChannel() {
+        @Override
+        public ManagedChannel create() {
           /* Use its own event loop thread pool to avoid blocking. */
+          if (eventGroup == null) {
+            eventGroup =
+                new NioEventLoopGroup(1, new DefaultThreadFactory("handshaker pool", true));
+          }
+          return NettyChannelBuilder.forTarget("metadata.google.internal:8080")
+              .directExecutor()
+              .eventLoopGroup(eventGroup)
+              .usePlaintext()
+              .build();
+        }
+
+        @Override
+        public void close(ManagedChannel instance) {
+          instance.shutdownNow();
+          if (eventGroup != null) {
+            eventGroup.shutdownGracefully();
+          }
+        }
+
+        @Override
+        public String toString() {
+          return "grpc-alts-handshaker-service-channel";
+        }
+      };
+
+  /** Returns a fixed object pool of handshaker service channel for testing only. */
+  static FixedObjectPool<ManagedChannel> getHandshakerChannelPoolForTesting(
+      String handshakerAddress) {
     ThreadFactory clientThreadFactory = new DefaultThreadFactory("handshaker pool", true);
     ManagedChannel channel =
         NettyChannelBuilder.forTarget(handshakerAddress)
@@ -60,13 +75,6 @@ final class HandshakerServiceChannel {
             .eventLoopGroup(new NioEventLoopGroup(1, clientThreadFactory))
             .usePlaintext()
             .build();
-    return channel;
-  }
-
-  public static synchronized ManagedChannel get() {
-    if (channel == null) {
-      channel = createChannel();
-    }
-    return channel;
+    return new FixedObjectPool<ManagedChannel>(channel);
   }
 }