fix: update TransferManager downloads to reduce in memory buffering (#2630)

BenWhitehead · web-flow · commit fc2fd750ed60 · 2024-07-08T17:51:57.000-04:00
diff --git a/google-cloud-storage/src/main/java/com/google/cloud/storage/transfermanager/ChunkedDownloadCallable.java b/google-cloud-storage/src/main/java/com/google/cloud/storage/transfermanager/ChunkedDownloadCallable.java
@@ -58,9 +58,10 @@ final class ChunkedDownloadCallable implements Callable<DownloadSegment> {
   @Override
   public DownloadSegment call() {
     long bytesCopied = -1L;
-    try (ReadChannel rc = storage.reader(originalBlob.getBlobId(), opts)) {
-      FileChannel wc =
-          FileChannel.open(destPath, StandardOpenOption.WRITE, StandardOpenOption.CREATE);
+    try (ReadChannel rc = storage.reader(originalBlob.getBlobId(), opts);
+        FileChannel wc =
+            FileChannel.open(destPath, StandardOpenOption.WRITE, StandardOpenOption.CREATE)) {
+      rc.setChunkSize(0);
       rc.seek(startPosition);
       rc.limit(endPosition);
       wc.position(startPosition);
diff --git a/google-cloud-storage/src/main/java/com/google/cloud/storage/transfermanager/DirectDownloadCallable.java b/google-cloud-storage/src/main/java/com/google/cloud/storage/transfermanager/DirectDownloadCallable.java
@@ -52,14 +52,15 @@ public DownloadResult call() {
     Path path = TransferManagerUtils.createDestPath(parallelDownloadConfig, originalBlob);
     long bytesCopied = -1L;
     try (ReadChannel rc =
-        storage.reader(
-            BlobId.of(parallelDownloadConfig.getBucketName(), originalBlob.getName()), opts)) {
-      FileChannel wc =
-          FileChannel.open(
-              path,
-              StandardOpenOption.WRITE,
-              StandardOpenOption.CREATE,
-              StandardOpenOption.TRUNCATE_EXISTING);
+            storage.reader(
+                BlobId.of(parallelDownloadConfig.getBucketName(), originalBlob.getName()), opts);
+        FileChannel wc =
+            FileChannel.open(
+                path,
+                StandardOpenOption.WRITE,
+                StandardOpenOption.CREATE,
+                StandardOpenOption.TRUNCATE_EXISTING)) {
+      rc.setChunkSize(0);
       bytesCopied = ByteStreams.copy(rc, wc);
       if (originalBlob.getSize() != null) {
         if (bytesCopied != originalBlob.getSize()) {
