[Python] Add configuration.{connection_pool_maxsize, assert_hostname} (#6508)

* Backport kubernetes client features:

- assert_hostname
- connection_pool_maxsize
- cleanups

* Update petstore sample

samples/client/petstore/python/petstore_api/api_client.py

@@ -283,7 +283,7 @@ class ApiClient(object):
                  _request_timeout=None):
         """
         Makes the HTTP request (synchronous) and return the deserialized data.
-        To make an async request, define a function for callback.
+        To make an async request, set the async parameter.
 
         :param resource_path: Path to method endpoint.
         :param method: Method to call.
@@ -307,10 +307,10 @@ class ApiClient(object):
         :param _request_timeout: timeout setting for this request. If one number provided, it will be total request
                                  timeout. It can also be a pair (tuple) of (connection, read) timeouts.
         :return:
-            If provide parameter callback,
+            If async parameter is True,
             the request will be called asynchronously.
             The method will return the request thread.
-            If parameter callback is None,
+            If parameter async is False or missing,
             then the method will return the response directly.
         """
         if not async:

samples/client/petstore/python/petstore_api/configuration.py

@@ -15,8 +15,9 @@ from __future__ import absolute_import
 
 import urllib3
 
-import sys
 import logging
+import multiprocessing
+import sys
 
 from six import iteritems
 from six.moves import http_client as httplib
@@ -75,6 +76,16 @@ class Configuration(object):
         self.cert_file = None
         # client key file
         self.key_file = None
+        # Set this to True/False to enable/disable SSL hostname verification.
+        self.assert_hostname = None
+
+        # urllib3 connection pool's maximum number of connections saved
+        # per pool. urllib3 uses 1 connection as default value, but this is
+        # not the best value when you are making a lot of possibly parallel
+        # requests to the same host, which is often the case here.
+        # cpu_count * 5 is used as default value to increase performance.
+        self.connection_pool_maxsize = multiprocessing.cpu_count() * 5
+
 
         # Proxy URL
         self.proxy = None

samples/client/petstore/python/petstore_api/rest.py

@@ -56,7 +56,7 @@ class RESTResponse(io.IOBase):
 
 class RESTClientObject(object):
 
-    def __init__(self, configuration, pools_size=4, maxsize=4):
+    def __init__(self, configuration, pools_size=4, maxsize=None):
         # urllib3.PoolManager will pass all kw parameters to connectionpool
         # https://github.com/shazow/urllib3/blob/f9409436f83aeb79fbaf090181cd81b784f1b8ce/urllib3/poolmanager.py#L75
         # https://github.com/shazow/urllib3/blob/f9409436f83aeb79fbaf090181cd81b784f1b8ce/urllib3/connectionpool.py#L680
@@ -76,6 +76,16 @@ class RESTClientObject(object):
             # if not set certificate file, use Mozilla's root certificates.
             ca_certs = certifi.where()
 
+        addition_pool_args = {}
+        if configuration.assert_hostname is not None:
+            addition_pool_args['assert_hostname'] = config.assert_hostname
+
+        if maxsize is None:
+            if configuration.connection_pool_maxsize is not None:
+                maxsize = configuration.connection_pool_maxsize
+            else:
+                maxsize = 4
+
         # https pool manager
         if configuration.proxy:
             self.pool_manager = urllib3.ProxyManager(
@@ -85,7 +95,8 @@ class RESTClientObject(object):
                 ca_certs=ca_certs,
                 cert_file=configuration.cert_file,
                 key_file=configuration.key_file,
-                proxy_url=configuration.proxy
+                proxy_url=configuration.proxy,
+                **addition_pool_args
             )
         else:
             self.pool_manager = urllib3.PoolManager(
@@ -94,7 +105,8 @@ class RESTClientObject(object):
                 cert_reqs=cert_reqs,
                 ca_certs=ca_certs,
                 cert_file=configuration.cert_file,
-                key_file=configuration.key_file
+                key_file=configuration.key_file,
+                **addition_pool_args
             )
 
     def request(self, method, url, query_params=None, headers=None,