Improve documentation + more cleanups

Author: alextwoods

services-custom/s3-transfer-manager/src/main/java/software/amazon/awssdk/transfer/s3/internal/GenericS3TransferManager.java

@@ -215,14 +215,13 @@ public FileUpload uploadFile(UploadFileRequest uploadFileRequest) {
         TransferProgressUpdater progressUpdater = new TransferProgressUpdater(uploadFileRequest,
                                                                               requestBody.contentLength().orElse(null));
         progressUpdater.transferInitiated();
-        boolean multipartEnabled = isS3ClientMultipartEnabled();
         requestBody = progressUpdater.wrapRequestBody(requestBody, false);
 
         progressUpdater.registerCompletion(returnFuture);
 
         PutObjectRequest putObjectRequest = uploadFileRequest.putObjectRequest();
         PauseObservable pauseObservable;
-        if (multipartEnabled) {
+        if (isS3ClientMultipartEnabled()) {
             pauseObservable = new PauseObservable();
             Consumer<AwsRequestOverrideConfiguration.Builder> attachObservableAndListener =
                 b -> b.putExecutionAttribute(PAUSE_OBSERVABLE, pauseObservable)

services-custom/s3-transfer-manager/src/main/java/software/amazon/awssdk/transfer/s3/progress/TransferListener.java

@@ -72,10 +72,14 @@
  *     <li>Be mindful that {@link #bytesTransferred(Context.BytesTransferred)} may be called extremely often (subject to I/O
  *     buffer sizes). Be careful in implementing expensive operations as a side effect. Consider rate-limiting your side
  *     effect operations, if needed.</li>
- *     <li>In the case of uploads, there may be some delay between the bytes being fully transferred and the transfer
+ *     <li>In the case of multipart uploads, there may be some delay between the bytes being fully transferred and the transfer
  *     successfully completing. Internally, {@link S3TransferManager} uses the Amazon S3
  *     <a href="https://docs.aws.amazon.com/AmazonS3/latest/userguide/mpuoverview.html">multipart upload API</a>
  *     and must finalize uploads with a {@link CompleteMultipartUploadRequest}.</li>
+ *     <li>For single part in-memory uploads, 100% of the bytes are read immediately into memory and progress is only
+ *     reported once, after all bytes are sent and the HTTP response is received.</li>
+ *     <li>For single part file uploads, progress is reported when bytes are read from the file rather than when bytes are sent
+ *     so there will be some delay between when progress reaching 100% and the transfer successfully completing.</li>
  *     <li>{@link TransferListener}s may be invoked by different threads. If your {@link TransferListener} is stateful,
  *     ensure that it is also thread-safe.</li>
  *     <li>{@link TransferListener}s are not intended to be used for control flow, and therefore your implementation

services-custom/s3-transfer-manager/src/test/java/software/amazon/awssdk/transfer/s3/internal/TransferProgressUpdaterTest.java

@@ -256,7 +256,7 @@ public void exceptionOccurred(Throwable error) {
 
 
     @Test
-    void wrapRequestBody_suppressProgress_doesNotReportProgress() {
+    void wrapRequestBody_disableIncrementalProgress_doesNotReportProgress() {
         byte[] data = new byte[1024];
         Arrays.fill(data, (byte) 'a');
         long contentLength = data.length;
@@ -293,7 +293,7 @@ public void onComplete() {
             }
         });
 
-        // When suppressProgress is true, the wrapper should NOT report any progress.
+        // When disableIncrementalProgress is true, the wrapper should NOT report any progress.
         // Progress is instead reported by the JAVA_PROGRESS_LISTENER after the server responds.
         assertThat(bytesAfterOnNext.get()).isNotNull();
         assertThat(bytesAfterOnNext.get()).isEqualTo(0L);