Use http Keep-Alive, else BigQuery queries are ~seconds slower than n…

…ecessary (#195)

- Before (without Keep-Alive): ~3-7s for BigQuery `select 3` with an already cached result
- After (with Keep-Alive): ~1.5-3s
- Query sends these 6 http requests and runtime appears to be dominated by network RTT

datalab/utils/_http.py

@@ -53,6 +53,16 @@ class Http(object):
  """A helper class for making HTTP requests.
  """
 
+ # Reuse one Http object across requests to take advantage of Keep-Alive, e.g.
+ # for BigQuery queries that requires at least ~5 sequential http requests.
+ #
+ # TODO(nikhilko):
+ # SSL cert validation seemingly fails, and workarounds are not amenable
+ # to implementing in library code. So configure the Http object to skip
+ # doing so, in the interim.
+ http = httplib2.Http()
+ http.disable_ssl_certificate_validation = True
+
  def __init__(self):
  pass
 
@@ -109,15 +119,8 @@ def request(url, args=None, data=None, headers=None, method=None,
  if method is None:
  method = 'GET'
 
- # Create an Http object to issue requests. Associate the credentials
- # with it if specified to perform authorization.
- #
- # TODO(nikhilko):
- # SSL cert validation seemingly fails, and workarounds are not amenable
- # to implementing in library code. So configure the Http object to skip
- # doing so, in the interim.
- http = httplib2.Http()
- http.disable_ssl_certificate_validation = True
+ # Authorize with credentials if given.
+ http = Http.http
  if credentials is not None:
  http = credentials.authorize(http)
  if stats is not None:

tests/_util/http_tests.py

@@ -23,7 +23,7 @@
 class TestCases(unittest.TestCase):
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_get_request_is_invoked(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, '{}')
 
@@ -32,23 +32,23 @@ def test_get_request_is_invoked(self, mock_request, mock_response):
  self.assertEqual(mock_request.call_args[1]['method'], 'GET')
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_post_request_is_invoked(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, '{}')
 
  Http.request('http://www.example.org', data={})
  self.assertEqual(mock_request.call_args[1]['method'], 'POST')
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_explicit_post_request_is_invoked(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, '{}')
 
  Http.request('http://www.example.org', method='POST')
  self.assertEqual(mock_request.call_args[1]['method'], 'POST')
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_query_string_format(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, '{}')
 
@@ -59,7 +59,7 @@ def test_query_string_format(self, mock_request, mock_response):
  self.assertTrue('b=a+b+c' in parts[1:])
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_formats_json_request(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, '{}')
 
@@ -71,7 +71,7 @@ def test_formats_json_request(self, mock_request, mock_response):
  'application/json')
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_supports_custom_content(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, '{}')
 
@@ -83,15 +83,15 @@ def test_supports_custom_content(self, mock_request, mock_response):
  self.assertEqual(mock_request.call_args[1]['headers']['Content-Type'], 'text/plain')
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_parses_json_response(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, '{"abc":123}')
 
  data = Http.request('http://www.example.org')
  self.assertEqual(data['abc'], 123)
 
  @mock.patch('httplib2.Response')
- @mock.patch('httplib2.Http.request')
+ @mock.patch('datalab.utils._http.Http.http.request')
  def test_raises_http_error(self, mock_request, mock_response):
  TestCases._setup_mocks(mock_request, mock_response, 'Not Found', 404)