Make ChannelPool work.

Author: yihanzhen

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java

@@ -16,15 +16,15 @@
 
 package com.google.cloud.spanner;
 
-import com.google.cloud.grpc.GrpcTransportOptions;
 import com.google.cloud.ServiceDefaults;
 import com.google.cloud.ServiceOptions;
 import com.google.cloud.ServiceRpc;
 import com.google.cloud.TransportOptions;
+import com.google.cloud.grpc.GrpcTransportOptions;
+import com.google.cloud.spanner.spi.SpannerRpcFactory;
 import com.google.cloud.spanner.spi.v1.GapicSpannerRpc;
 import com.google.cloud.spanner.spi.v1.GrpcSpannerRpc;
 import com.google.cloud.spanner.spi.v1.SpannerRpc;
-import com.google.cloud.spanner.spi.SpannerRpcFactory;
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
@@ -218,6 +218,10 @@ public List<ManagedChannel> getRpcChannels() {
     return rpcChannels;
   }
 
+  public int getNumChannels() {
+    return numChannels;
+  }
+
   public SessionPoolOptions getSessionPoolOptions() {
     return sessionPoolOptions;
   }
@@ -353,4 +357,15 @@ protected SpannerRpc getGapicSpannerRpc() {
   public Builder toBuilder() {
     return new Builder(this);
   }
+
+  public String getEndpoint() {
+    URL url;
+    try {
+      url = new URL(getHost());
+    } catch (MalformedURLException e) {
+      throw new IllegalArgumentException("Invalid host: " + getHost(), e);
+    }
+    return String.format(
+        "%s:%s", url.getHost(), url.getPort() < 0 ? url.getDefaultPort() : url.getPort());
+  }
 }

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

@@ -24,6 +24,7 @@
 import com.google.api.gax.grpc.GaxGrpcProperties;
 import com.google.api.gax.grpc.GrpcCallContext;
 import com.google.api.gax.grpc.GrpcTransportChannel;
+import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
 import com.google.api.gax.longrunning.OperationFuture;
 import com.google.api.gax.rpc.ApiClientHeaderProvider;
 import com.google.api.gax.rpc.FixedTransportChannelProvider;
@@ -106,7 +107,8 @@ public class GapicSpannerRpc implements SpannerRpc {
 
   private static final PathTemplate PROJECT_NAME_TEMPLATE =
       PathTemplate.create("projects/{project}");
-
+  private static final int MAX_MESSAGE_SIZE = 100 * 1024 * 1024;
+  
   private final SpannerStub stub;
   private final InstanceAdminStub instanceStub;
   private final DatabaseAdminStub databaseStub;
@@ -143,17 +145,18 @@ public GapicSpannerRpc(SpannerOptions options) throws IOException {
             mergedHeaderProvider.getHeaders(),
             internalHeaderProviderBuilder.getResourceHeaderKey());
 
-    // TODO(pongad): make channel pool work
-
     // TODO(pongad): make RPC logging work (formerly LoggingInterceptor)
     // TODO(pongad): add watchdog
     // TODO(pongad): make error augmentation work (formerly SpannerErrorInterceptor)
 
     TransportChannelProvider channelProvider =
-        FixedTransportChannelProvider.create(
-            GrpcTransportChannel.newBuilder()
-                .setManagedChannel(options.getRpcChannels().get(0))
-                .build());
+        InstantiatingGrpcChannelProvider
+            .newBuilder()
+            .setEndpoint(options.getEndpoint())
+            .setMaxInboundMessageSize(MAX_MESSAGE_SIZE)
+            .setPoolSize(options.getNumChannels())
+            .build();
+
     CredentialsProvider credentialsProvider =
         GrpcTransportOptions.setUpCredentialsProvider(options);