Merge b22baa0c19 into db7f8b8bb6

docker/api/client.py

@@ -350,6 +350,12 @@ class APIClient(
             # fine because we won't be doing TLS over them
             pass
 
+        if six.PY3:
+            # Preserve the io.BufferedReader buffer as part of the socket so
+            # that it may be read ahead of attempting futher reads from the
+            # socket -- see ..utils.socket.read() implementation.
+            setattr(sock, '_buffer', memoryview(response.raw._fp.fp.peek()))
+
         return sock
 
     def _stream_helper(self, response, decode=False):

docker/utils/socket.py

@@ -28,6 +28,30 @@ def read(socket, n=4096):
     Reads at most n bytes from socket
     """
 
+    # This socket may have been extracted from an HTTPResponse. That would have
+    # wrapped the socked with an io.BufferedReader, which may still have some
+    # "unread" bytes in its internal buffer. If that were the case, those would
+    # be preserved inside _buffer attribute of the socket (see
+    # ..api.client.APIClient._get_raw_response_socket() implementation). These
+    # must be returned firsts, before attemting any further reads from the
+    # socket.
+    if not hasattr(socket, '_buffer') or not socket._buffer:
+        return read_from_socket(socket, n)
+
+    ret, socket._buffer = socket._buffer[:n], socket._buffer[n:]
+
+    still_to_read = n - len(ret)
+    if still_to_read:
+        return ret.tobytes() + read_from_socket(socket, still_to_read)
+    else:
+        return ret.tobytes()
+
+
+def read_from_socket(socket, n=4096):
+    """
+    Reads at most n bytes from socket
+    """
+
     recoverable_errors = (errno.EINTR, errno.EDEADLK, errno.EWOULDBLOCK)
 
     if not isinstance(socket, NpipeSocket):