feat: optimize dataflow job start by making sample row keys lighter (#4075)

Change-Id: I27718a29b6a48994462c215d02b43c407f2d8958

Author: igorbernstein2

bigtable-dataflow-parent/bigtable-hbase-beam/src/main/java/com/google/cloud/bigtable/batch/common/CloudBigtableServiceImpl.java

@@ -16,7 +16,10 @@
 package com.google.cloud.bigtable.batch.common;
 
 import com.google.bigtable.repackaged.com.google.api.core.InternalApi;
+import com.google.bigtable.repackaged.com.google.api.gax.grpc.ChannelPoolSettings;
+import com.google.bigtable.repackaged.com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
 import com.google.bigtable.repackaged.com.google.cloud.bigtable.data.v2.BigtableDataClient;
+import com.google.bigtable.repackaged.com.google.cloud.bigtable.data.v2.BigtableDataSettings;
 import com.google.bigtable.repackaged.com.google.cloud.bigtable.data.v2.models.KeyOffset;
 import com.google.cloud.bigtable.beam.CloudBigtableTableConfiguration;
 import com.google.cloud.bigtable.hbase.wrappers.veneer.BigtableHBaseVeneerSettings;
@@ -32,8 +35,26 @@ public List<KeyOffset> getSampleRowKeys(CloudBigtableTableConfiguration config)
 
  // TODO: figure out how to stick to HBase api here
  BigtableHBaseVeneerSettings settings =
- (BigtableHBaseVeneerSettings) BigtableHBaseVeneerSettings.create(config.toHBaseConfig());
- try (BigtableDataClient client = BigtableDataClient.create(settings.getDataSettings())) {
+ BigtableHBaseVeneerSettings.create(config.toHBaseConfig());
+
+ // Lighten the client instance since it's only used for a single RPC
+ BigtableDataSettings.Builder builder = settings.getDataSettings().toBuilder();
+ InstantiatingGrpcChannelProvider oldTransportProvider =
+ (InstantiatingGrpcChannelProvider)
+ settings.getDataSettings().getStubSettings().getTransportChannelProvider();
+
+ builder
+ .stubSettings()
+ .setTransportChannelProvider(
+ oldTransportProvider
+ .toBuilder()
+ .setChannelPoolSettings(
+ ChannelPoolSettings.staticallySized(1)
+ .toBuilder()
+ .setPreemptiveRefreshEnabled(false)
+ .build())
+ .build());
+ try (BigtableDataClient client = BigtableDataClient.create(builder.build())) {
  return client.sampleRowKeys(config.getTableId());
  }
  }