test_requests.py

#
# Copyright (c) 2015-2018 Canonical, Ltd.
#
# This file is part of Talisker
# (see http://github.com/canonical-ols/talisker).
#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.
#
from __future__ import unicode_literals
from __future__ import print_function
from __future__ import division
from __future__ import absolute_import

from builtins import *  # noqa
from future.utils import native_str

from collections import namedtuple
from datetime import datetime, timedelta
import http.client
import io
import itertools
import os
import requests
import responses
import socket
import time
from future.moves.urllib.parse import urlunsplit

from freezegun import freeze_time
import pytest
import urllib3

from talisker import Context
import talisker.requests
import talisker.statsd
import talisker.testing


def request(method='GET', host='http://example.com', url='/', **kwargs):
    req = requests.Request(method, url=host + url, **kwargs)
    return req.prepare()


def mock_response(
        req=None,
        code=200,
        view=None,
        body=None,
        content_type='text/plain',
        headers={},
        elapsed=1.0):
    if req is None:
        req = request()
    resp = requests.Response()
    resp.request = req
    resp.status_code = code
    resp.elapsed = timedelta(seconds=elapsed)
    resp.headers['Server'] = 'test/1.0'
    if body is not None:
        resp.raw = io.StringIO(body)
        resp.headers['Content-Length'] = len(body)
        resp.headers['Content-Type'] = content_type
    if view is not None:
        resp.headers['X-View-Name'] = view
    resp.headers.update(headers)
    return resp


def test_collect_metadata():
    req = request(url='/foo/bar')
    metadata = talisker.requests.collect_metadata(req, None)
    assert metadata == {
        'url': 'http://example.com/foo/bar',
        'method': 'GET',
        'host': 'example.com',
    }


@pytest.fixture
def requests_hosts(monkeypatch):
    monkeypatch.setattr(talisker.requests, 'HOSTS', {})


def test_collect_metadata_hostname(requests_hosts):
    talisker.requests.register_endpoint_name('1.2.3.4:8000', 'service')
    req = request(url='/foo/bar', host='http://1.2.3.4:8000')
    metadata = talisker.requests.collect_metadata(req, None)
    assert metadata == {
        'url': 'http://service:8000/foo/bar',
        'method': 'GET',
        'host': 'service',
        'netloc': '1.2.3.4:8000',
    }


def test_collect_metadata_request_body():
    req = request(method='POST', url='/foo/bar', json=u'"some data"')
    metadata = talisker.requests.collect_metadata(req, None)
    assert metadata == {
        'url': 'http://example.com/foo/bar',
        'method': 'POST',
        'host': 'example.com',
        'request_type': 'application/json',
        'request_size': 15,
    }


def test_collect_metadata_querystring():
    req = request(url='/foo/bar?baz=1&qux=data')
    metadata = talisker.requests.collect_metadata(req, None)
    assert metadata == {
        'url': 'http://example.com/foo/bar?',
        'qs': '?baz=<len 1>&qux=<len 4>',
        'qs_size': 14,
        'method': 'GET',
        'host': 'example.com',
    }


def test_collect_metadata_with_response():
    req = request(url='/foo/bar')
    resp = mock_response(req, view='views.name', body=u'some content')
    metadata = talisker.requests.collect_metadata(req, resp)
    assert metadata == {
        'url': 'http://example.com/foo/bar',
        'method': 'GET',
        'host': 'example.com',
        'status_code': 200,
        'view': 'views.name',
        'server': 'test/1.0',
        'duration_ms': 1000,
        'response_type': 'text/plain',
        'response_size': 12,
    }


def test_metric_hook(context, get_breadcrumbs):
    r = mock_response(view='view')

    talisker.requests.metrics_response_hook(r)

    assert context.statsd[0] == 'requests.count.example-com.view:1|c'
    assert context.statsd[1] == (
        'requests.latency.example-com.view.200:1000.000000|ms'
    )

    breadcrumbs = get_breadcrumbs()
    if breadcrumbs is not None:
        assert breadcrumbs[0]['type'] == 'http'
        assert breadcrumbs[0]['category'] == 'requests'
        assert breadcrumbs[0]['data']['url'] == 'http://example.com/'
        assert breadcrumbs[0]['data']['host'] == 'example.com'
        assert breadcrumbs[0]['data']['method'] == 'GET'
        assert breadcrumbs[0]['data']['view'] == 'view'
        assert breadcrumbs[0]['data']['status_code'] == 200
        assert breadcrumbs[0]['data']['duration_ms'] == 1000.0


def test_metric_hook_user_name(context, get_breadcrumbs):
    r = mock_response(view='view')

    Context.current.metric_api_name = 'api'
    Context.current.metric_host_name = 'service'
    talisker.requests.metrics_response_hook(r)

    assert context.statsd[0] == 'requests.count.service.api:1|c'
    assert context.statsd[1] == (
        'requests.latency.service.api.200:1000.000000|ms'
    )
    breadcrumbs = get_breadcrumbs()
    if breadcrumbs is not None:
        assert breadcrumbs[0]['type'] == 'http'
        assert breadcrumbs[0]['category'] == 'requests'
        assert breadcrumbs[0]['data']['url'] == 'http://example.com/'
        assert breadcrumbs[0]['data']['host'] == 'example.com'
        assert breadcrumbs[0]['data']['view'] == 'view'
        assert breadcrumbs[0]['data']['method'] == 'GET'
        assert breadcrumbs[0]['data']['status_code'] == 200
        assert breadcrumbs[0]['data']['duration_ms'] == 1000.0


def test_metric_hook_registered_endpoint(
        requests_hosts, context, get_breadcrumbs):
    talisker.requests.register_endpoint_name('1.2.3.4', 'service')
    req = request(host='http://1.2.3.4', url='/foo/bar?a=1')
    resp = mock_response(req, view='view')

    talisker.requests.metrics_response_hook(resp)

    assert context.statsd[0] == 'requests.count.service.view:1|c'
    assert context.statsd[1] == (
        'requests.latency.service.view.200:1000.000000|ms'
    )
    breadcrumbs = get_breadcrumbs()
    if breadcrumbs is not None:
        assert breadcrumbs[0]['type'] == 'http'
        assert breadcrumbs[0]['category'] == 'requests'
        assert breadcrumbs[0]['data']['url'] == 'http://service/foo/bar?'
        assert breadcrumbs[0]['data']['host'] == 'service'
        assert breadcrumbs[0]['data']['netloc'] == '1.2.3.4'
        assert breadcrumbs[0]['data']['method'] == 'GET'
        assert breadcrumbs[0]['data']['view'] == 'view'
        assert breadcrumbs[0]['data']['status_code'] == 200
        assert breadcrumbs[0]['data']['duration_ms'] == 1000.0


@responses.activate
def test_configured_session(context, get_breadcrumbs):
    deadline = time.time() + 10
    expected_deadline = datetime.utcfromtimestamp(deadline).isoformat() + 'Z'
    Context.set_debug()
    Context.current.deadline = deadline
    session = requests.Session()
    talisker.requests.configure(session)

    responses.add(
        responses.GET,
        'http://localhost/foo/bar',
        body='OK',
        headers={'X-View-Name': 'view'},
    )

    with talisker.testing.request_id('XXX'):
        session.get('http://localhost/foo/bar')

    for header_name in responses.calls[0].request.headers:
        assert isinstance(header_name, native_str)
    headers = responses.calls[0].request.headers
    assert headers['X-Request-Id'] == 'XXX'
    assert headers['X-Request-Deadline'] == expected_deadline
    assert headers['X-Debug'] == '1'
    assert context.statsd[0] == 'requests.count.localhost.view:1|c'
    assert context.statsd[1].startswith(
        'requests.latency.localhost.view.200:')

    breadcrumbs = get_breadcrumbs()
    if breadcrumbs is not None:
        assert breadcrumbs[0]['type'] == 'http'
        assert breadcrumbs[0]['category'] == 'requests'
        assert breadcrumbs[0]['data']['url'] == 'http://localhost/foo/bar'
        assert breadcrumbs[0]['data']['host'] == 'localhost'
        assert breadcrumbs[0]['data']['view'] == 'view'
        assert breadcrumbs[0]['data']['method'] == 'GET'
        assert breadcrumbs[0]['data']['status_code'] == 200
        assert 'duration_ms' in breadcrumbs[0]['data']


@responses.activate
def test_configured_session_http_error(context, get_breadcrumbs):
    session = requests.Session()
    talisker.requests.configure(session)

    responses.add(
        responses.GET,
        'http://localhost/foo/bar',
        status=500,
        body='NOT OK',
        headers={'X-View-Name': 'view'},
    )

    session.get('http://localhost/foo/bar')

    assert context.statsd[0] == 'requests.count.localhost.view:1|c'
    assert context.statsd[1].startswith('requests.latency.localhost.view.500:')
    assert context.statsd[2] == (
        'requests.errors.localhost.http.view.500:1|c'
    )

    breadcrumbs = get_breadcrumbs()
    if breadcrumbs is not None:
        assert breadcrumbs[0]['type'] == 'http'
        assert breadcrumbs[0]['category'] == 'requests'
        assert breadcrumbs[0]['data']['url'] == 'http://localhost/foo/bar'
        assert breadcrumbs[0]['data']['host'] == 'localhost'
        assert breadcrumbs[0]['data']['view'] == 'view'
        assert breadcrumbs[0]['data']['method'] == 'GET'
        assert breadcrumbs[0]['data']['status_code'] == 500
        assert 'duration_ms' in breadcrumbs[0]['data']


def test_configured_session_connection_error(context, get_breadcrumbs):
    session = requests.Session()
    talisker.requests.configure(session)

    with pytest.raises(requests.exceptions.ConnectionError):
        session.get('http://nope.nowhere/foo')

    assert context.statsd[0] == 'requests.count.nope-nowhere.unknown:1|c'
    assert context.statsd[1].startswith(
        'requests.errors.nope-nowhere.connection.unknown.')
    # error code depends on python version host dns set up
    assert any((
        context.statsd[1].endswith('unknown:1|c'),
        context.statsd[1].endswith('EAI_NONAME:1|c'),
        context.statsd[1].endswith('EAI_AGAIN:1|c'),
    ))

    breadcrumbs = get_breadcrumbs()
    if breadcrumbs is not None:
        assert breadcrumbs[-1]['type'] == 'http'
        assert breadcrumbs[-1]['category'] == 'requests'
        assert breadcrumbs[-1]['data']['url'] == 'http://nope.nowhere/foo'
        assert breadcrumbs[-1]['data']['host'] == 'nope.nowhere'
        assert breadcrumbs[-1]['data']['method'] == 'GET'
        if 'errno' in breadcrumbs[-1]['data']:
            assert any((
                breadcrumbs[-1]['data']['errno'] == 'EAI_NONAME',
                breadcrumbs[-1]['data']['errno'] == 'EAI_AGAIN',
            ))


@responses.activate
def test_configured_session_with_user_name(context):
    session = requests.Session()
    talisker.requests.configure(session)

    responses.add(responses.GET, 'http://localhost/foo/bar', body='OK')

    with talisker.testing.request_id('XXX'):
        session.get(
            'http://localhost/foo/bar',
            metric_api_name='api',
            metric_host_name='service',
        )

    for header_name in responses.calls[0].request.headers:
        assert isinstance(header_name, native_str)
    assert responses.calls[0].request.headers['X-Request-Id'] == 'XXX'
    assert context.statsd[0].startswith('requests.count.service.api:')
    assert context.statsd[1].startswith('requests.latency.service.api.200:')


@pytest.fixture
def backends():
    return itertools.cycle([
        'http://1.2.3.4:8000',
        'http://1.2.3.4:8001',
        'http://4.3.2.1:8000',
    ])


@responses.activate
def test_adapter_balances(backends):
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter(backend_iter=backends)
    session.mount('http://name', adapter)
    responses.add('GET', 'http://1.2.3.4:8000/foo', body='1')
    responses.add('GET', 'http://1.2.3.4:8001/foo', body='2')
    responses.add('GET', 'http://4.3.2.1:8000/foo', body='3')

    result = session.get('http://name/foo').text
    result += session.get('http://name/foo').text
    result += session.get('http://name/foo').text
    assert ''.join(sorted(result)) == '123'


def test_adapter_requires_consistent_http_scheme(backends):
    with pytest.raises(ValueError):
        talisker.requests.TaliskerAdapter(backends=['localhost'])
    with pytest.raises(ValueError):
        talisker.requests.TaliskerAdapter(backends=['ftp://localhost'])
    with pytest.raises(ValueError):
        talisker.requests.TaliskerAdapter(
            backends=['http://localhost', 'https://otherhost'])


@pytest.fixture
def send_kwargs(monkeypatch):
    kws = {}

    def send(*args, **kwargs):
        kws.update(kwargs)
        return requests.Response()

    monkeypatch.setattr(requests.adapters.HTTPAdapter, 'send', send)

    return kws


def test_adapter_adds_default_timeout(send_kwargs):
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter()
    session.mount('http://name', adapter)
    session.get('http://name/foo')
    assert send_kwargs['timeout'] == (1.0, 10.0)


@freeze_time()
def test_adapter_respects_context_timeout(send_kwargs):
    Context.current.set_deadline(500)
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter()
    session.mount('http://name', adapter)
    session.get('http://name/foo')
    assert send_kwargs['timeout'] == (0.5, 0.5)


def test_adapter_raises_when_context_deadline_exceeded():
    Context.current.set_deadline(0)
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter()
    session.mount('http://name', adapter)
    with pytest.raises(talisker.DeadlineExceeded):
        session.get('http://name/foo')


class FakeSocket():
    """Pretend to be read only socket-like object that implements makefile."""
    def __init__(self, content):
        self.content = content

    def makefile(self, mode, buffer=None):
        return io.BytesIO(self.content)


class RequestData(namedtuple('RequestData', 'pool conn method url kwargs')):

    @property
    def full_url(self):
        netloc = self.conn.host
        if self.conn.port:
            netloc += ':{}'.format(self.conn.port)
        return urlunsplit((
            self.pool.scheme,
            netloc,
            self.url,
            None,
            None,
        ))

    @property
    def read_timeout(self):
        return self.kwargs['timeout'].read_timeout

    @property
    def connect_timeout(self):
        return self.kwargs['timeout'].connect_timeout

    @property
    def timeout(self):
        return self.connect_timeout, self.read_timeout


class Urllib3Mock:
    """Helper to mock out urllib3 requests and timings."""
    def __init__(self, frozen_time):
        self.frozen_time = frozen_time
        self.requests = []
        self.response_iter = None

    def set_response(self, content, status='200 OK', headers={}, latency=1.0):
        """Set the response to any requests."""
        self.response_iter = itertools.cycle(
            [((content, status, headers), latency)]
        )

    def set_error(self, error, latency=1.0):
        """Raise an error for all requests."""
        assert isinstance(error, Exception)
        self.response_iter = itertools.cycle(
            [
                (error, latency)])

    def set_responses(self, responses):
        """Respond to requests with provided responses in order.

        Responses can be Exceptions to raise or a http.client.HTTPResponse."""
        self.response_iter = iter(responses)

    def make_response(self, content, status='200 OK', headers={}):
        """Make a fake http.client.HTTPResponse based on a byte stream."""
        formatted_headers = '\r\n'.join(
            '{}: {}'.format(k, v) for k, v in headers.items()
        )
        stream = 'HTTP/1.1 {}\r\n{}\r\n{}'.format(
            status, formatted_headers, content,
        )
        sock = FakeSocket(stream.encode('utf8'))
        response = http.client.HTTPResponse(sock)
        response.begin()  # parse the stream
        return response

    def make_request(self, pool, conn, method, url, **kwargs):
        """A mock replacement for urllib3.HTTPConnectionPool._make_request."""
        rdata = RequestData(pool, conn, method, url, kwargs)
        self.requests.append(rdata)

        assert self.response_iter, 'no responses set'

        response, latency = next(self.response_iter)
        self.frozen_time.tick(timedelta(seconds=latency))

        if isinstance(response, Exception):
            raise response
        elif isinstance(response, http.client.HTTPResponse):
            return response
        elif isinstance(response, str):
            return self.make_response(response)
        else:
            return self.make_response(*response)

    @property
    def call_list(self):
        return [(r.full_url, r.timeout) for r in self.requests]


@pytest.fixture
def mock_urllib3(monkeypatch):
    freeze = freeze_time()
    frozen = freeze.start()
    mock = Urllib3Mock(frozen)

    def sleep(amount):
        frozen.tick(timedelta(seconds=amount))

    # use a function to wrap the method, so we preserve original calling self
    # reference, rather than our method's self.
    def _make_request(*args, **kwargs):
        return mock.make_request(*args, **kwargs)

    monkeypatch.setattr(
        urllib3.HTTPConnectionPool, '_make_request', _make_request)
    monkeypatch.setattr(urllib3.util.retry.time, 'sleep', sleep)
    yield mock
    freeze.stop()


def test_adapter_default_no_retries(mock_urllib3):
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter()
    session.mount('http://name', adapter)

    mock_urllib3.set_error(socket.error())

    with pytest.raises(requests.ConnectionError):
        session.get('http://name')

    assert len(mock_urllib3.requests) == 1


@pytest.mark.parametrize('urllib3_error, requests_error', [
    (urllib3.exceptions.ConnectTimeoutError(None, 'error'),
        requests.ConnectionError),
    (socket.error(), requests.ConnectionError),
])
def test_adapter_retry_on_errors(
        backends, mock_urllib3, urllib3_error, requests_error):
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter(
        backend_iter=backends,
        max_retries=urllib3.Retry(3, backoff_factor=1),
    )
    session.mount('http://name', adapter)
    mock_urllib3.set_error(urllib3_error)

    with pytest.raises(requests_error):
        session.get('http://name/foo')

    assert mock_urllib3.call_list == [
        ('http://1.2.3.4:8000/foo', (1.0, 10.0)),
        ('http://1.2.3.4:8001/foo', (1.0, 9.0)),
        ('http://4.3.2.1:8000/foo', (1.0, 6.0)),
        ('http://1.2.3.4:8000/foo', (1.0, 1.0)),
    ]


def test_adapter_no_retry_on_read_timeout(mock_urllib3):
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter(
        ['http://1.2.3.4:8000'],
        max_retries=urllib3.Retry(3),
    )
    session.mount('http://name', adapter)

    mock_urllib3.set_error(
        urllib3.exceptions.ReadTimeoutError(None, '/', 'error')
    )
    with pytest.raises(requests.Timeout):
        session.get('http://name/foo')

    urls = list(request.full_url for request in mock_urllib3.requests)
    assert urls == ['http://1.2.3.4:8000/foo']


def test_adapter_retry_on_status_raises(mock_urllib3, backends):
    session = requests.Session()
    retry = urllib3.Retry(3, backoff_factor=1, status_forcelist=[503])
    adapter = talisker.requests.TaliskerAdapter(
        backend_iter=backends,
        max_retries=retry,
    )
    session.mount('http://name', adapter)

    mock_urllib3.set_response('OH NOES', '503 Service Unavailable')

    with pytest.raises(requests.exceptions.RetryError):
        session.get('http://name/foo')

    assert mock_urllib3.call_list == [
        ('http://1.2.3.4:8000/foo', (1.0, 10.0)),
        ('http://1.2.3.4:8001/foo', (1.0, 9.0)),
        ('http://4.3.2.1:8000/foo', (1.0, 6.0)),
        ('http://1.2.3.4:8000/foo', (1.0, 1.0)),
    ]


def test_adapter_retry_on_status_returns_when_no_raise(mock_urllib3, backends):
    session = requests.Session()
    retry = urllib3.Retry(
        3, backoff_factor=1, status_forcelist=[503], raise_on_status=False,
    )
    adapter = talisker.requests.TaliskerAdapter(
        backend_iter=backends,
        max_retries=retry,
    )
    session.mount('http://name', adapter)

    mock_urllib3.set_response('OH NOES', '503 Service Unavailable')
    response = session.get('http://name/foo')
    assert response.status_code == 503
    assert response.content == b'OH NOES'

    assert mock_urllib3.call_list == [
        ('http://1.2.3.4:8000/foo', (1.0, 10.0)),
        ('http://1.2.3.4:8001/foo', (1.0, 9.0)),
        ('http://4.3.2.1:8000/foo', (1.0, 6.0)),
        ('http://1.2.3.4:8000/foo', (1.0, 1.0)),
    ]


def test_adapter_retry_on_status_header(mock_urllib3, backends):
    session = requests.Session()
    retry = urllib3.Retry(3, backoff_factor=1, status_forcelist=[503])
    adapter = talisker.requests.TaliskerAdapter(
        backend_iter=backends,
        max_retries=retry,
    )
    session.mount('http://name', adapter)

    headers = {'Retry-After': '1'}
    mock_urllib3.set_response(
        'OH NOES', '503 Service Unavailable', headers)

    with pytest.raises(requests.exceptions.RetryError):
        session.get('http://name/foo')

    assert mock_urllib3.call_list == [
        ('http://1.2.3.4:8000/foo', (1.0, 10.0)),
        ('http://1.2.3.4:8001/foo', (1.0, 8.0)),
        ('http://4.3.2.1:8000/foo', (1.0, 6.0)),
        ('http://1.2.3.4:8000/foo', (1.0, 4.0)),
    ]


@pytest.mark.parametrize('retry, response', [
    (None, socket.error()),
    (urllib3.Retry(1), socket.error()),
    (urllib3.Retry(1, status_forcelist=[500]),
        ('ERROR', '500 Internal Server Error')),
])
def test_adapter_exceptions_match_default(mock_urllib3, retry, response):
    session = requests.Session()
    session.mount(
        'http://default',
        requests.adapters.HTTPAdapter(max_retries=retry),
    )
    session.mount(
        'http://talisker',
        talisker.requests.TaliskerAdapter(max_retries=retry),
    )
    if isinstance(response, Exception):
        mock_urllib3.set_error(response)
    else:
        mock_urllib3.set_response(*response)

    exc = None
    try:
        session.get('http://default/')
    except Exception as e:
        exc = e

    with pytest.raises(exc.__class__):
        session.get('http://talisker/')


def test_adapter_timeout_formats(mock_urllib3):
    session = requests.Session()
    retry = urllib3.Retry(3, backoff_factor=1)
    no_retries = urllib3.Retry(0, read=False)
    adapter = talisker.requests.TaliskerAdapter(
        ['http://1.2.4.5'],
        max_retries=retry,
    )
    session.mount('http://name', adapter)

    mock_urllib3.set_error(socket.error())

    with pytest.raises(requests.ConnectionError):
        session.get('http://name/foo', timeout=no_retries)
    assert len(mock_urllib3.requests) == 1
    assert mock_urllib3.requests[-1].timeout == (1.0, 10.0)

    with pytest.raises(requests.ConnectionError):
        session.get('http://name/foo', timeout=(5.0, no_retries))
    assert len(mock_urllib3.requests) == 2
    assert mock_urllib3.requests[-1].timeout == (1.0, 5.0)

    with pytest.raises(requests.ConnectionError):
        session.get('http://name/foo', timeout=(2.0, 5.0, no_retries))
    assert len(mock_urllib3.requests) == 3
    assert mock_urllib3.requests[-1].timeout == (2.0, 5.0)


def test_adapter_bad_timeout_raises():
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter()
    session.mount('http://name', adapter)

    with pytest.raises(ValueError):
        session.get('http://name/foo', timeout="string")
    with pytest.raises(ValueError):
        session.get('http://name/foo', timeout=(1, 2, 3, 4))
    with pytest.raises(ValueError):
        session.get('http://name/foo', timeout=(1, 2, 3))


def test_adapter_callsite_retries(mock_urllib3, backends):
    session = requests.Session()
    adapter = talisker.requests.TaliskerAdapter(backend_iter=backends)
    session.mount('http://name', adapter)

    mock_urllib3.set_error(socket.error())

    with pytest.raises(requests.ConnectionError):
        session.get('http://name/foo')

    assert mock_urllib3.call_list == [
        ('http://1.2.3.4:8000/foo', (1.0, 10.0)),
    ]

    with pytest.raises(requests.exceptions.ConnectionError):
        retry = urllib3.Retry(3, backoff_factor=1)
        session.get('http://name/foo', timeout=retry)

    assert mock_urllib3.call_list[1:] == [
        ('http://1.2.3.4:8001/foo', (1.0, 10.0)),
        ('http://4.3.2.1:8000/foo', (1.0, 9.0)),
        ('http://1.2.3.4:8000/foo', (1.0, 6.0)),
        ('http://1.2.3.4:8001/foo', (1.0, 1.0)),
    ]


def test_threadlocal_forking():
    session = talisker.requests.get_session()
    if os.fork() == 0:
        new_session = talisker.requests.get_session()
        assert new_session is not session
        os._exit(0)