perf: Set gcsUploadBufferSizeBytes to 8MB for Export Jobs to reduce RAM usage (#4366)

Author: justinuang

bigtable-dataflow-parent/bigtable-beam-import/src/main/java/com/google/cloud/bigtable/beam/sequencefiles/ExportJob.java

@@ -23,6 +23,7 @@
 import org.apache.beam.sdk.Pipeline;
 import org.apache.beam.sdk.PipelineResult;
 import org.apache.beam.sdk.extensions.gcp.options.GcpOptions;
+import org.apache.beam.sdk.extensions.gcp.options.GcsOptions;
 import org.apache.beam.sdk.io.DefaultFilenamePolicy;
 import org.apache.beam.sdk.io.FileSystems;
 import org.apache.beam.sdk.io.Read;
@@ -95,7 +96,10 @@
  */
 @InternalExtensionOnly
 public class ExportJob {
-  public interface ExportOptions extends GcpOptions {
+
+  static final int GCS_UPLOAD_BUFFER_SIZE_BYTES_DEFAULT = 8388608;
+
+  public interface ExportOptions extends GcpOptions, GcsOptions {
     @Description("This Bigtable App Profile id.")
     ValueProvider<String> getBigtableAppProfileId();
 
@@ -182,6 +186,9 @@ public static void main(String[] args) {
 
     ExportOptions opts =
         PipelineOptionsFactory.fromArgs(args).withValidation().as(ExportOptions.class);
+    if (opts.getGcsUploadBufferSizeBytes() == null) {
+      opts.setGcsUploadBufferSizeBytes(GCS_UPLOAD_BUFFER_SIZE_BYTES_DEFAULT);
+    }
 
     Pipeline pipeline = buildPipeline(opts);