Is it possible to refresh a session in requests?

Question

I create a session using requests.Session(). For some reason the server side closes this connection, so I have to reconnect. The problem is, this session is used in many places, so I'm wondering is it possible to rebuild a TCP connection but keep the session object so that I can still use it?

Example:

s = requests.Session()

class B:
    def __init__(self, session):
        self._session = session

    def get(self):
        self._session.get('some_url')

b1 = B(s)
b2 = B(s)
b3 = B(s)

# some get calls
...
# then connection is closed

# some get calls
...

If I could keep the seesion object, there's no need to replace every _session in every B instance.

Error log:

Traceback (most recent call last):
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/connectionpool.py", line 376, in _make_request
    httplib_response = conn.getresponse(buffering=True)
TypeError: getresponse() got an unexpected keyword argument 'buffering'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/connectionpool.py", line 559, in urlopen
    body=body, headers=headers)
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/connectionpool.py", line 378, in _make_request
    httplib_response = conn.getresponse()
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/http/client.py", line 1174, in getresponse
    response.begin()
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/http/client.py", line 282, in begin
    version, status, reason = self._read_status()
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/http/client.py", line 243, in _read_status
    line = str(self.fp.readline(_MAXLINE + 1), "iso-8859-1")
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/socket.py", line 571, in readinto
    return self._sock.recv_into(b)
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/ssl.py", line 924, in recv_into
    return self.read(nbytes, buffer)
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/ssl.py", line 786, in read
    return self._sslobj.read(len, buffer)
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/ssl.py", line 570, in read
    v = self._sslobj.read(len, buffer)
ConnectionResetError: [Errno 54] Connection reset by peer

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.5/site-packages/requests/adapters.py", line 376, in send
    timeout=timeout
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/connectionpool.py", line 609, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/util/retry.py", line 247, in increment
    raise six.reraise(type(error), error, _stacktrace)
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/packages/six.py", line 309, in reraise
    raise value.with_traceback(tb)
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/connectionpool.py", line 559, in urlopen
    body=body, headers=headers)
  File "/usr/local/lib/python3.5/site-packages/requests/packages/urllib3/connectionpool.py", line 378, in _make_request
    httplib_response = conn.getresponse()
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/http/client.py", line 1174, in getresponse
    response.begin()
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/http/client.py", line 282, in begin
    version, status, reason = self._read_status()
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/http/client.py", line 243, in _read_status
    line = str(self.fp.readline(_MAXLINE + 1), "iso-8859-1")
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/socket.py", line 571, in readinto
    return self._sock.recv_into(b)
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/ssl.py", line 924, in recv_into
    return self.read(nbytes, buffer)
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/ssl.py", line 786, in read
    return self._sslobj.read(len, buffer)
  File "/usr/local/Cellar/python3/3.5.0/Frameworks/Python.framework/Versions/3.5/lib/python3.5/ssl.py", line 570, in read
    v = self._sslobj.read(len, buffer)
requests.packages.urllib3.exceptions.ProtocolError: ('Connection aborted.', ConnectionResetError(54, 'Connection reset by peer'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/laike9m/ICT/zhihu-analysis/dynamic/main.py", line 108, in <module>
    main()
  File "/Users/laike9m/ICT/zhihu-analysis/dynamic/main.py", line 89, in main
    m.detect_new_question()
  File "/Users/laike9m/ICT/zhihu-analysis/dynamic/monitor.py", line 32, in detect_new_question
    question = latest_question = next(it)
  File "/usr/local/lib/python3.5/site-packages/zhihu/topic.py", line 269, in questions
    res = self._session.get(question_url, params=params)
  File "/usr/local/lib/python3.5/site-packages/requests/sessions.py", line 480, in get
    return self.request('GET', url, **kwargs)
  File "/usr/local/lib/python3.5/site-packages/requests/sessions.py", line 468, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python3.5/site-packages/requests/sessions.py", line 576, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python3.5/site-packages/requests/adapters.py", line 426, in send
    raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', ConnectionResetError(54, 'Connection reset by peer'))

This is a very common issue: Python handling socket.error: [Errno 104] Connection reset by peer. I don't have control over the server so I don't know why or how this happens.

The server does support keep-alive cause I'm able to make hundreds of requests(the period lasts for an hour or more).

HTTP connections are stateless, so even with Keep-Alive closing is the norm. Are you confusing cookie expiration with connections being closed perhaps? — Martijn Pieters
Unless you're using HTTP/2.x which is the new version of the HTTP protocol, what @MartijnPieters says is correct. But it would be interesting to see if Python does implement a "refresh" to the request library to better match HTTP/2.x. — Torxed
@Torxed: the requests library doesn't support HTTP/2.x. Not yet, at any rate. — Martijn Pieters
@MartijnPieters Good clarification. I simply made my comment for future readers and for those who try to run a web-server in strict mode (not enabling legacy protocols). And stated that it would be interesting in the future to see if Python does implement such a feature considering there is support for it in the protocol in the form of PING. I guess the official Python lib in the future will support the protocol in it's fullest form tho so I guess my remark is redundant. — Torxed
@laike9m: the session object creates connections as needed from the pool and supports keep-alive. If the server claims to support keep-alive but closes the connections prematurely without communicating this, then the server is broken. — Martijn Pieters

Martijn Pieters Martijn Pieters · Accepted Answer · 2016-01-12T15:39:38

Either make your B() a singleton, or make the session a class attribute (and thereby effectively a global).

For example, making it a class attribute only when you create at least one instance could look like this:

class B:
    def __init__(self):
        if not hasattr(type(self), '_session'):
            self._create_session()

    @classmethod
    def _create_session(cls):
        cls._session = requests.Session()

    def get(self):
        self._session.get('some_url')

If using the session can raise an exception because the server is not closing a session connection correctly, just re-create the session at that time:

    def __init__(self):
        if not hasattr(type(self), '_session'):
            self._create_session()

    @classmethod
    def _create_session(cls):
        cls._session = requests.Session()

    def get(self):
        retries = 5
        while retries:
            try:
                return self._session.get('some_url')
            except requests.ConnectionException as e:
                last_connection_exception = e
                retries -= 1
        raise last_connection_exception

The above example retries up to 5 times. You do not need to re-create the session each time. If a connection has been closed, even with an exception, the session object will just create a new TCP/IP connection for the next request.

If you find that the session object is somehow shot and no longer capable of creating new connections, while a fresh session does work, then that'd be a bug. Please report that to the project with a suitable MCVE.

Is it possible to refresh a session in requests?

1 Answers