Refactor session handling to allow options (Fixes Unidata#117)

This turns the collection of functions dealing with HTTP access into a
class that holds the options and returns properly constructed Sessions.
This allows setting up basic authentication options.

siphon/catalog.py

@@ -18,7 +18,7 @@
     # Python 3
     from urllib.parse import urljoin, urlparse
 
-from .http_util import create_http_session, urlopen
+from .http_util import session_manager
 from .metadata import TDSCatalogMetadata
 
 logging.basicConfig(level=logging.ERROR)
@@ -250,7 +250,7 @@ def __init__(self, catalog_url):
             The URL of a THREDDS client catalog
 
         """
-        session = create_http_session()
+        session = session_manager.create_session()
 
         # get catalog.xml file
         resp = session.get(catalog_url)
@@ -488,7 +488,7 @@ def resolve_url(self, catalog_url):
         if catalog_url != '':
             resolver_base = catalog_url.split('catalog.xml')[0]
             resolver_url = resolver_base + self.url_path
-            resolver_xml = urlopen(resolver_url)
+            resolver_xml = session_manager.urlopen(resolver_url)
             tree = ET.parse(resolver_xml)
             root = tree.getroot()
             if 'name' in root.attrib:
@@ -682,7 +682,7 @@ def access_with_service(self, service):
             from .ncss import NCSS
             provider = NCSS
         elif service == 'HTTPServer':
-            provider = urlopen
+            provider = session_manager.urlopen
         else:
             raise ValueError(service + ' is not an access method supported by Siphon')
 

siphon/cdmr/tests/test_ncstream.py

@@ -29,8 +29,8 @@ def get_test_latest_url(query=None):
 @recorder.use_cassette('latest_rap_ncstream_header')
 def get_header_remote():
     """Get a header from a remote data source."""
-    from siphon.http_util import urlopen
-    return urlopen(get_test_latest_url('req=header'))
+    from siphon.http_util import session_manager
+    return session_manager.urlopen(get_test_latest_url('req=header'))
 
 
 @pytest.mark.parametrize('src, result', [(b'\xb6\xe0\x02', 45110), (b'\x17\n\x0b', 23)])

siphon/http_util.py

@@ -18,8 +18,6 @@
 
 from . import __version__
 
-user_agent = 'Siphon ({})'.format(__version__)
-
 HTTPError = requests.HTTPError
 
 
@@ -49,49 +47,74 @@ def dst(self, dt):  # pylint:disable=unused-argument
 utc = UTC()
 
 
-def create_http_session():
-    """Create a new HTTP session with our user-agent set.
+class HTTPSessionManager(object):
+    """Manage the creation of sessions for HTTP access."""
 
-    Returns
-    -------
-    session : requests.Session
-        The created session
+    def __init__(self):
+        """Initialize ``HTTPSessionManager``."""
+        self.user_agent = 'Siphon ({})'.format(__version__)
+        self.options = {}
 
-    See Also
-    --------
-    urlopen
+    def set_session_options(self, **kwargs):
+        """Set options for created session instances.
 
-    """
-    ret = requests.Session()
-    ret.headers['User-Agent'] = user_agent
-    return ret
+        Takes keyword arguments and sets them as attributes on the returned
+        :class:`requests.Session` instance.
 
+        See Also
+        --------
+        create_session
 
-def urlopen(url, **kwargs):
-    """GET a file-like object for a URL using HTTP.
+        """
+        self.options = kwargs
 
-    This is a thin wrapper around :meth:`requests.Session.get` that returns a file-like object
-    wrapped around the resulting content.
+    def create_session(self):
+        """Create a new HTTP session with our user-agent set.
 
-    Parameters
-    ----------
-    url : str
-        The URL to request
+        Returns
+        -------
+        session : requests.Session
+            The created session
 
-    kwargs : arbitrary keyword arguments
-        Additional keyword arguments to pass to :meth:`requests.Session.get`.
+        See Also
+        --------
+        urlopen, set_session_options
 
-    Returns
-    -------
-    fobj : file-like object
-        A file-like interface to the content in the response
+        """
+        ret = requests.Session()
+        ret.headers['User-Agent'] = self.user_agent
+        for k, v in self.options.items():
+            setattr(ret, k, v)
+        return ret
 
-    See Also
-    --------
-    :meth:`requests.Session.get`
+    def urlopen(self, url, **kwargs):
+        """GET a file-like object for a URL using HTTP.
 
-    """
-    return BytesIO(create_http_session().get(url, **kwargs).content)
+        This is a thin wrapper around :meth:`requests.Session.get` that returns a file-like
+        object wrapped around the resulting content.
+
+        Parameters
+        ----------
+        url : str
+            The URL to request
+
+        kwargs : arbitrary keyword arguments
+            Additional keyword arguments to pass to :meth:`requests.Session.get`.
+
+        Returns
+        -------
+        fobj : file-like object
+            A file-like interface to the content in the response
+
+        See Also
+        --------
+        :meth:`requests.Session.get`
+
+        """
+        return BytesIO(self.create_session().get(url, **kwargs).content)
+
+
+session_manager = HTTPSessionManager()
 
 
 def parse_iso_date(s):
@@ -352,7 +375,7 @@ def __init__(self, url):
 
         """
         self._base = url
-        self._session = create_http_session()
+        self._session = session_manager.create_session()
         self._get_metadata()
 
     def get_query(self, query):

siphon/simplewebservice/acis.py

@@ -5,7 +5,7 @@
 
 import requests
 
-from ..http_util import create_http_session
+from ..http_util import session_manager
 
 
 def acis_request(method, params):
@@ -51,7 +51,8 @@ def acis_request(method, params):
     timeout = 300 if method == 'MultiStnData' else 60
 
     try:
-        response = create_http_session().post(base_url + method, json=params, timeout=timeout)
+        response = session_manager.create_session().post(base_url + method, json=params,
+                                                         timeout=timeout)
         return response.json()
     except requests.exceptions.Timeout:
         raise AcisApiException('Connection Timeout')

siphon/tests/test_http_util.py

@@ -7,8 +7,8 @@
 
 import pytest
 
-from siphon.http_util import (create_http_session, DataQuery, HTTPEndPoint, HTTPError,
-                              parse_iso_date, urlopen, utc)
+from siphon.http_util import (DataQuery, HTTPEndPoint, HTTPError,
+                              parse_iso_date, session_manager, utc)
 import siphon.testing
 
 recorder = siphon.testing.get_recorder(__file__)
@@ -17,18 +17,30 @@
 @recorder.use_cassette('top_thredds_catalog')
 def test_urlopen():
     """Test siphon's urlopen wrapper."""
-    fobj = urlopen('http://thredds-test.unidata.ucar.edu/thredds/catalog.xml')
+    fobj = session_manager.urlopen('http://thredds-test.unidata.ucar.edu/thredds/catalog.xml')
     assert fobj.read(2) == b'<?'
 
 
 @recorder.use_cassette('top_thredds_catalog')
 def test_session():
-    """Test that https sessions contain the proper user agent."""
-    session = create_http_session()
+    """Test that http sessions contain the proper user agent."""
+    session = session_manager.create_session()
     resp = session.get('http://thredds-test.unidata.ucar.edu/thredds/catalog.xml')
     assert resp.request.headers['user-agent'].startswith('Siphon')
 
 
+@recorder.use_cassette('top_thredds_catalog')
+def test_session_options():
+    """Test that http sessions receive proper options."""
+    auth = ('foo', 'bar')
+    session_manager.set_session_options(auth=auth)
+    try:
+        session = session_manager.create_session()
+        assert session.auth == auth
+    finally:
+        session_manager.set_session_options()
+
+
 def test_parse_iso():
     """Test parsing ISO-formatted dates."""
     parsed = parse_iso_date('2015-06-15T12:00:00Z')

siphon/tests/test_ncss_dataset.py

@@ -6,7 +6,7 @@
 import logging
 import xml.etree.ElementTree as ET
 
-from siphon.http_util import urlopen
+from siphon.http_util import session_manager
 from siphon.ncss_dataset import _Types, NCSSDataset
 from siphon.testing import get_recorder
 
@@ -559,7 +559,7 @@ def test_dataset_elements_full_ncss_station():
     """Test parsing the dataset from a full ncss station page."""
     url = ('http://thredds.ucar.edu/thredds/ncss/nws/synoptic/'
            'ncdecoded/Surface_Synoptic_Point_Data_fc.cdmr/dataset.xml')
-    element = ET.fromstring(urlopen(url).read())
+    element = ET.fromstring(session_manager.urlopen(url).read())
     parsed = NCSSDataset(element)
     assert parsed
 
@@ -570,7 +570,7 @@ def test_dataset_elements_full_ncss_grid():
     url = ('http://thredds.ucar.edu/thredds/ncss/grib/NCEP/GFS/'
            'Global_0p5deg/GFS_Global_0p5deg_20150602_0000.grib2/'
            'dataset.xml')
-    element = ET.fromstring(urlopen(url).read())
+    element = ET.fromstring(session_manager.urlopen(url).read())
     parsed = NCSSDataset(element)
     assert parsed
 
@@ -580,6 +580,6 @@ def test_dataset_parsing_tds5(recwarn):
     """Test parsing the dataset from TDS 5."""
     url = ('http://thredds-test.unidata.ucar.edu/thredds/ncss/grid/casestudies/irma/model/'
            'gfs/GFS_Global_0p5deg_20170903_1200.grib2/dataset.xml')
-    element = ET.fromstring(urlopen(url).read())
+    element = ET.fromstring(session_manager.urlopen(url).read())
     NCSSDataset(element)
     assert len(recwarn) == 0