Don't create parallel request if download is about to complete

content/browser/download/parallel_download_job_unittest.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/download/parallel_download_job.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/memory/ptr_util.h"
@@ skipping 66 matching lines @@
 class ParallelDownloadJobTest : public testing::Test {
  public:
   void CreateParallelJob(int64_t initial_request_offset,
                          int64_t content_length,
                          const DownloadItem::ReceivedSlices& slices,
                          int request_count,
                          int64_t min_slice_size) {
     item_delegate_ = base::MakeUnique<DownloadItemImplDelegate>();
     download_item_ = base::MakeUnique<NiceMock<MockDownloadItemImpl>>(
         item_delegate_.get(), slices);
+    EXPECT_CALL(*download_item_, GetTotalBytes())
+        .WillRepeatedly(
+            testing::Return(initial_request_offset + content_length));
+    EXPECT_CALL(*download_item_, GetReceivedBytes())
+        .WillRepeatedly(testing::Return(initial_request_offset));
+
     DownloadCreateInfo info;
     info.offset = initial_request_offset;
     info.total_bytes = content_length;
     std::unique_ptr<MockDownloadRequestHandle> request_handle =
         base::MakeUnique<MockDownloadRequestHandle>();
     mock_request_handle_ = request_handle.get();
     job_ = base::MakeUnique<ParallelDownloadJobForTest>(
         download_item_.get(), std::move(request_handle), info, request_count,
         min_slice_size);
   }
@@ skipping 86 matching lines @@
   // Task 1:  Range:44-70, for 27 bytes.
   // Task 2:  Range:71-, for 29 bytes.
   DownloadItem::ReceivedSlices slices = {DownloadItem::ReceivedSlice(0, 17)};
   CreateParallelJob(12, 88, slices, 3, 1);
   BuildParallelRequests();
   EXPECT_EQ(2, static_cast<int>(job_->workers().size()));
   VerifyWorker(44, 27);
   VerifyWorker(71, 0);
   DestroyParallelJob();
 
   // File size: 100 bytes.

[xingliu, 2017/04/08 02:21:05]

nit: Can we add a TODO here to pass the minimum remaining time here as  a
parameter in CreateParallelJob after it's a finch configuration? 

So other test cases don't need to change with this configuration accordingly.

[qinmin, 2017/04/10 19:04:48]

Done.

-  // Received slices: [0, 98], Range:0-97.
-  // Original request: Range:98-. Content-length: 2.
-  // 2 bytes left for 4 requests. Only 1 additional request.
-  // Original request: Range:98-99, for 1 bytes.
-  // Task 1:  Range:99-, for 1 bytes.
-  slices = {DownloadItem::ReceivedSlice(0, 98)};
-  CreateParallelJob(98, 2, slices, 4, 1);
+  // Received slices: [0, 60], Range:0-59.
+  // Original request: Range:60-. Content-length: 40.
+  // 40 bytes left for 4 requests. Only 1 additional request.
+  // Original request: Range:60-79, for 20 bytes.
+  // Task 1:  Range:80-, for 20 bytes.
+  slices = {DownloadItem::ReceivedSlice(0, 60)};
+  CreateParallelJob(60, 40, slices, 4, 20);
   BuildParallelRequests();
   EXPECT_EQ(1, static_cast<int>(job_->workers().size()));
-  VerifyWorker(99, 0);
+  VerifyWorker(80, 0);
   DestroyParallelJob();
 
   // Content-Length is 0, no additional requests.
   slices = {DownloadItem::ReceivedSlice(0, 100)};
   CreateParallelJob(100, 0, slices, 3, 1);
   BuildParallelRequests();
   EXPECT_TRUE(job_->workers().empty());
   DestroyParallelJob();
 
   // File size: 100 bytes.
@@ skipping 75 matching lines @@
     EXPECT_CALL(*job_.get(), CountOnByteStreamReady());
     std::unique_ptr<MockDownloadRequestHandle> mock_handle =
         base::MakeUnique<MockDownloadRequestHandle>();
     EXPECT_CALL(*mock_handle.get(), PauseRequest());
     MakeWorkerReady(worker.second.get(), std::move(mock_handle));
   }
 
   DestroyParallelJob();
 }
 
+// Test that parallel request is not created if the remaining content can be
+// finish downloading soon.
+TEST_F(ParallelDownloadJobTest, RemainingContentWillFinishSoon) {
+  DownloadItem::ReceivedSlices slices = {DownloadItem::ReceivedSlice(0, 99)};
+  CreateParallelJob(99, 1, slices, 3, 1);
+  BuildParallelRequests();
+  EXPECT_EQ(0, static_cast<int>(job_->workers().size()));
+
+  DestroyParallelJob();
+}
+
 }  // namespace content