Universally-compatible reading of chunked streams

Docker introduced newlines in stream output in version 0.9
(https://github.com/dotcloud/docker/pull/4276), but not to all
endpoints - POST /images/create, for example, does not include them.

This reverts to the old, less pleasant implementation of
_stream_helper(), with a manual check for newlines to fix the problem
described in #176 and fixed in #184, without the accompanying
regression. It should work against Docker 0.8, 0.9 and 0.10, both when
building and when pulling.

docker/client.py

@@ -209,9 +209,23 @@ class Client(requests.Session):
 
     def _stream_helper(self, response):
         """Generator for data coming from a chunked-encoded HTTP response."""
-        for line in response.iter_lines(chunk_size=32):
-            if line:
-                yield line
+        socket_fp = self._get_raw_response_socket(response)
+        socket_fp.setblocking(1)
+        socket = socket_fp.makefile()
+        while True:
+            # Because Docker introduced newlines at the end of chunks in v0.9,
+            # and only on some API endpoints, we have to cater for both cases.
+            size_line = socket.readline()
+            if size_line == '\r\n':
+                size_line = socket.readline()
+
+            size = int(size_line, 16)
+            if size <= 0:
+                break
+            data = socket.readline()
+            if not data:
+                break
+            yield data
 
     def _multiplexed_buffer_helper(self, response):
         """A generator of multiplexed data blocks read from a buffered

tests/integration_test.py

@@ -14,6 +14,7 @@
 
 import time
 import base64
+import json
 import io
 import os
 import signal
@@ -666,10 +667,8 @@ class TestPullStream(BaseTestCase):
         self.assertIn('Images', info)
         img_count = info['Images']
         stream = self.client.pull('joffrey/test001', stream=True)
-        res = u''
         for chunk in stream:
-            res += chunk
-        self.assertEqual(type(res), six.text_type)
+            json.loads(chunk)  # ensure chunk is a single, valid JSON blob
         self.assertEqual(img_count + 3, self.client.info()['Images'])
         img_info = self.client.inspect_image('joffrey/test001')
         self.assertIn('id', img_info)
@@ -762,6 +761,7 @@ class TestBuildStream(BaseTestCase):
         stream = self.client.build(fileobj=script, stream=True)
         logs = ''
         for chunk in stream:
+            json.loads(chunk)  # ensure chunk is a single, valid JSON blob
             logs += chunk
         self.assertNotEqual(logs, '')