feat: resizing channel pool size based on the work load

Author: mutianf

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

@@ -24,6 +24,7 @@
 import com.google.api.gax.batching.FlowController.LimitExceededBehavior;
 import com.google.api.gax.core.FixedCredentialsProvider;
 import com.google.api.gax.core.GoogleCredentialsProvider;
+import com.google.api.gax.grpc.ChannelPoolSettings;
 import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
 import com.google.api.gax.retrying.RetrySettings;
 import com.google.api.gax.rpc.FixedHeaderProvider;
@@ -250,7 +251,13 @@ public Map<String, String> getJwtAudienceMapping() {
  /** Returns a builder for the default ChannelProvider for this service. */
  public static InstantiatingGrpcChannelProvider.Builder defaultGrpcTransportProviderBuilder() {
  return BigtableStubSettings.defaultGrpcTransportProviderBuilder()
- .setPoolSize(getDefaultChannelPoolSize())
+ .setChannelPoolSettings(
+ ChannelPoolSettings.builder()
+ .setInitialChannelCount(2)
+ .setMinRpcsPerChannel(1)
+ .setMaxRpcsPerChannel(50)
+ .setPreemptiveRefreshEnabled(true)
+ .build())
  .setMaxInboundMessageSize(MAX_MESSAGE_SIZE)
  .setKeepAliveTime(Duration.ofSeconds(30)) // sends ping in this interval
  .setKeepAliveTimeout(
@@ -260,11 +267,6 @@ public static InstantiatingGrpcChannelProvider.Builder defaultGrpcTransportProvi
  .setAttemptDirectPath(true);
  }
 
- static int getDefaultChannelPoolSize() {
- // TODO: tune channels
- return 2 * Runtime.getRuntime().availableProcessors();
- }
-
  @SuppressWarnings("WeakerAccess")
  public static TransportChannelProvider defaultTransportChannelProvider() {
  return defaultGrpcTransportProviderBuilder().build();
@@ -577,9 +579,7 @@ private Builder() {
  copyRetrySettings(baseDefaults.mutateRowSettings(), mutateRowSettings);
 
  long maxBulkMutateElementPerBatch = 100L;
- // Enables bulkMutate to support 10 outstanding batches upto per channel or up to 20K entries.
- long maxBulkMutateOutstandingElementCount =
- Math.min(20_000L, 10L * maxBulkMutateElementPerBatch * getDefaultChannelPoolSize());
+ long maxBulkMutateOutstandingElementCount = 20_000L;
 
  bulkMutateRowsSettings =
  BigtableBatchingCallSettings.newBuilder(new MutateRowsBatchingDescriptor())
@@ -601,9 +601,7 @@ private Builder() {
 
  long maxBulkReadElementPerBatch = 100L;
  long maxBulkReadRequestSizePerBatch = 400L * 1024L;
- // Enables bulkRead to support 10 outstanding batches per channel
- long maxBulkReadOutstandingElementCount =
- 10L * maxBulkReadElementPerBatch * getDefaultChannelPoolSize();
+ long maxBulkReadOutstandingElementCount = 20_000L;
 
  bulkReadRowsSettings =
  BigtableBulkReadRowsCallSettings.newBuilder(new ReadRowsBatchingDescriptor())