Recover from aborted tar.gz extraction

If download from google storage gets terminated while extracting .tar.gz
archive, it won't be extracted on the next run which results in invalid
workspace. This patches places a flag file if extraction wasn't
completed. Such flag is checked on next execution and forces re-download
if found.

This does not fix currently broken workspaces.

R=dpranke@google.com, ehmladonado@chromium.org

Bug: 1189273
Change-Id: I4047d98c193493d9a0fe20a46043e1f8376e5c7e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2774085
Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

download_from_google_storage.py

@@ -254,9 +254,24 @@ def _downloader_worker_thread(thread_num, q, force, base_url,
         continue
       extract_dir = output_filename[:-len('.tar.gz')]
     if os.path.exists(output_filename) and not force:
-      if not extract or os.path.exists(extract_dir):
-        if get_sha1(output_filename) == input_sha1_sum:
-          continue
+      skip = get_sha1(output_filename) == input_sha1_sum
+      if extract:
+        # Additional condition for extract:
+        # 1) extract_dir must exist
+        # 2) .tmp flag file mustn't exist
+        if not os.path.exists(extract_dir):
+          out_q.put('%d> Extract dir %s does not exist, re-downloading...' %
+                    (thread_num, extract_dir))
+          skip = False
+        # .tmp file is created just before extraction and removed just after
+        # extraction. If such file exists, it means the process was terminated
+        # mid-extraction and therefore needs to be extracted again.
+        elif os.path.exists(extract_dir + '.tmp'):
+          out_q.put('%d> Detected tmp flag file for %s, '
+                    're-downloading...' % (thread_num, output_filename))
+          skip = False
+      if skip:
+        continue
     # Check if file exists.
     file_url = '%s/%s' % (base_url, input_sha1_sum)
     (code, _, err) = gsutil.check_call('ls', file_url)
@@ -336,7 +351,9 @@ def _downloader_worker_thread(thread_num, q, force, base_url,
         out_q.put('%d> Extracting %d entries from %s to %s' %
                   (thread_num, len(tar.getmembers()),output_filename,
                    extract_dir))
-        tar.extractall(path=dirname)
+        with open(extract_dir + '.tmp', 'a'):
+          tar.extractall(path=dirname)
+        os.remove(extract_dir + '.tmp')
     # Set executable bit.
     if sys.platform == 'cygwin':
       # Under cygwin, mark all files as executable. The executable flag in

tests/download_from_google_storage_unittest.py

@@ -295,6 +295,8 @@ class DownloadTests(unittest.TestCase):
     shutil.rmtree(output_dirname)
     sha1_hash = download_from_google_storage.get_sha1(output_filename)
     input_filename = '%s/%s' % (self.base_url, sha1_hash)
+
+    # Initial download
     self.queue.put((sha1_hash, output_filename))
     self.queue.put((None, None))
     stdout_queue = queue.Queue()
@@ -322,6 +324,64 @@ class DownloadTests(unittest.TestCase):
     self.assertTrue(os.path.exists(output_dirname))
     self.assertTrue(os.path.exists(extracted_filename))
 
+    # Test noop download
+    self.queue.put((sha1_hash, output_filename))
+    self.queue.put((None, None))
+    stdout_queue = queue.Queue()
+    download_from_google_storage._downloader_worker_thread(0,
+                                                           self.queue,
+                                                           False,
+                                                           self.base_url,
+                                                           self.gsutil,
+                                                           stdout_queue,
+                                                           self.ret_codes,
+                                                           True,
+                                                           True,
+                                                           delete=False)
+
+    self.assertEqual(list(stdout_queue.queue), [])
+    self.assertEqual(self.gsutil.history, expected_calls)
+    self.assertEqual(list(self.ret_codes.queue), [])
+    self.assertTrue(os.path.exists(output_dirname))
+    self.assertTrue(os.path.exists(extracted_filename))
+
+    # With dirty flag file, previous extraction wasn't complete
+    with open(os.path.join(self.base_path, 'subfolder.tmp'), 'a'):
+      pass
+
+    self.queue.put((sha1_hash, output_filename))
+    self.queue.put((None, None))
+    stdout_queue = queue.Queue()
+    download_from_google_storage._downloader_worker_thread(0,
+                                                           self.queue,
+                                                           False,
+                                                           self.base_url,
+                                                           self.gsutil,
+                                                           stdout_queue,
+                                                           self.ret_codes,
+                                                           True,
+                                                           True,
+                                                           delete=False)
+    expected_calls += [('check_call', ('ls', input_filename)),
+                       ('check_call', ('cp', input_filename, output_filename))]
+    if sys.platform != 'win32':
+      expected_calls.append(
+          ('check_call', ('stat', 'gs://sometesturl/%s' % sha1_hash)))
+    expected_output = [
+        '0> Detected tmp flag file for %s, re-downloading...' %
+        (output_filename),
+        '0> Downloading %s@%s...' % (output_filename, sha1_hash),
+        '0> Removed %s...' % (output_dirname),
+        '0> Extracting 3 entries from %s to %s' %
+        (output_filename, output_dirname),
+    ]
+    expected_ret_codes = []
+    self.assertEqual(list(stdout_queue.queue), expected_output)
+    self.assertEqual(self.gsutil.history, expected_calls)
+    self.assertEqual(list(self.ret_codes.queue), expected_ret_codes)
+    self.assertTrue(os.path.exists(output_dirname))
+    self.assertTrue(os.path.exists(extracted_filename))
+
   def test_download_worker_skips_not_found_file(self):
     sha1_hash = '7871c8e24da15bad8b0be2c36edc9dc77e37727f'
     input_filename = '%s/%s' % (self.base_url, sha1_hash)