Add HTTP_MAX_CLIENTS setting.

Add in support for the HTTP_MAX_CLIENTS environment variable to override the
default tornado settings.

README.rst

@@ -84,6 +84,15 @@ As with Tornado, to use the curl client which has numerous benefits:
        app.listen(8000)
        ioloop.IOLoop.current().start()
 
+Environment Variables
+---------------------
+
++------------------+----------------------------------------------------------+
+| HTTP_MAX_CLIENTS | An optional setting that specifies the maximum number of |
+|                  | simultaneous asynchronous HTTP requests. If not          |
+|                  | specified, the default Tornado value of 10 will be used. |
++------------------+----------------------------------------------------------+
+
 License
 -------
 ``sprockets.mixins.http`` is released under the `3-Clause BSD license <https://github.com/sprockets/sprockets.mixins.http/blob/master/LICENSE>`_.

sprockets/mixins/http/__init__.py

@@ -8,6 +8,7 @@ requests.
 import collections
 import json
 import logging
+import os
 import socket
 import time
 
@@ -22,6 +23,7 @@ LOGGER = logging.getLogger(__name__)
 CONTENT_TYPE_JSON = headers.parse_content_type('application/json')
 CONTENT_TYPE_MSGPACK = headers.parse_content_type('application/msgpack')
 DEFAULT_USER_AGENT = 'sprockets.mixins.http/{}'.format(__version__)
+DEFAULT_MAX_CLIENTS = 10
 
 
 HTTPResponse = collections.namedtuple(
@@ -99,7 +101,13 @@ class HTTPClientMixin(object):
         if body:
             body = self._http_req_body_serialize(
                 body, request_headers['Content-Type'])
+
         client = httpclient.AsyncHTTPClient()
+
+        # Workaround for Tornado defect.
+        if hasattr(client, 'max_clients') and os.getenv('HTTP_MAX_CLIENTS'):
+            client.max_clients = int(os.getenv('HTTP_MAX_CLIENTS'))
+
         response, start_time = None, time.time()
         for attempt in range(0, self.MAX_HTTP_RETRIES):
             LOGGER.debug('%s %s (Attempt %i of %i) %r',

tests.py

@@ -1,8 +1,9 @@
 import json
 import logging
+import os
 import uuid
 
-from tornado import httputil, testing, web
+from tornado import httpclient, httputil, testing, web
 import mock
 import umsgpack
 
@@ -400,6 +401,15 @@ class MixinTestCase(testing.AsyncHTTPTestCase):
             method='DELETE',
             body={'foo': 'bar', 'status_code': 200},
             allow_nonstandard_methods=True)
-
         self.assertTrue(response.ok)
-        self.assertEqual(response.code, 200)
+
+    @testing.gen_test()
+    def test_max_clients_settings_supported(self):
+        os.environ['HTTP_MAX_CLIENTS'] = '25'
+        response = yield self.mixin.http_fetch(
+            self.get_url('/test?foo=bar&status_code=200'))
+        self.assertTrue(response.ok)
+        del os.environ['HTTP_MAX_CLIENTS']
+        client = httpclient.AsyncHTTPClient()
+        self.assertEqual(client.max_clients, 25)
+