vcs-client: report more data about the call for better request tracking

rhodecode/lib/vcs/__init__.py

@@ -1,186 +1,190 b''
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2014-2020 RhodeCode GmbH
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License, version 3
 # (only), as published by the Free Software Foundation.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 # This program is dual-licensed. If you wish to learn more about the
 # RhodeCode Enterprise Edition, including its added features, Support services,
 # and proprietary license terms, please see https://rhodecode.com/licenses/
 
 """
 Various version Control System version lib (vcs) management abstraction layer
 for Python. Build with server client architecture.
 """
 import atexit
 import logging
 import urlparse
 from cStringIO import StringIO
 
 import rhodecode
 from rhodecode.lib.vcs.conf import settings
 from rhodecode.lib.vcs.backends import get_vcs_instance, get_backend
 from rhodecode.lib.vcs.exceptions import (
     VCSError, RepositoryError, CommitError, VCSCommunicationError)
 
 VERSION = (0, 5, 0, 'dev')
 
 __version__ = '.'.join((str(each) for each in VERSION[:4]))
 
 __all__ = [
     'get_version', 'get_vcs_instance', 'get_backend',
     'VCSError', 'RepositoryError', 'CommitError', 'VCSCommunicationError'
 ]
 
 log = logging.getLogger(__name__)
 
 # The pycurl library directly accesses C API functions and is not patched by
 # gevent. This will potentially lead to deadlocks due to incompatibility to
 # gevent. Therefore we check if gevent is active and import a gevent compatible
 # wrapper in that case.
 try:
     from gevent import monkey
     if monkey.is_module_patched('__builtin__'):
         import geventcurl as pycurl
         log.debug('Using gevent comapatible pycurl: %s', pycurl)
     else:
         import pycurl
 except ImportError:
     import pycurl
 
 
 def get_version():
     """
     Returns shorter version (digit parts only) as string.
     """
     return '.'.join((str(each) for each in VERSION[:3]))
 
 
 def connect_http(server_and_port):
     from rhodecode.lib.vcs import connection, client_http
     from rhodecode.lib.middleware.utils import scm_app
 
     session_factory = client_http.ThreadlocalSessionFactory()
 
     connection.Git = client_http.RemoteVCSMaker(
         server_and_port, '/git', 'git', session_factory)
     connection.Hg = client_http.RemoteVCSMaker(
         server_and_port, '/hg', 'hg', session_factory)
     connection.Svn = client_http.RemoteVCSMaker(
         server_and_port, '/svn', 'svn', session_factory)
     connection.Service = client_http.ServiceConnection(
         server_and_port, '/_service', session_factory)
 
     scm_app.HG_REMOTE_WSGI = client_http.VcsHttpProxy(
         server_and_port, '/proxy/hg')
     scm_app.GIT_REMOTE_WSGI = client_http.VcsHttpProxy(
         server_and_port, '/proxy/git')
 
     @atexit.register
     def free_connection_resources():
         connection.Git = None
         connection.Hg = None
         connection.Svn = None
         connection.Service = None
 
 
 def connect_vcs(server_and_port, protocol):
     """
     Initializes the connection to the vcs server.
 
     :param server_and_port: str, e.g. "localhost:9900"
     :param protocol: str or "http"
     """
     if protocol == 'http':
         connect_http(server_and_port)
     else:
         raise Exception('Invalid vcs server protocol "{}"'.format(protocol))
 
 
 class CurlSession(object):
     """
     Modeled so that it provides a subset of the requests interface.
 
     This has been created so that it does only provide a minimal API for our
     needs. The parts which it provides are based on the API of the library
     `requests` which allows us to easily benchmark against it.
 
     Please have a look at the class :class:`requests.Session` when you extend
     it.
     """
 
     def __init__(self):
         curl = pycurl.Curl()
         # TODO: johbo: I did test with 7.19 of libcurl. This version has
         # trouble with 100 - continue being set in the expect header. This
         # can lead to massive performance drops, switching it off here.
-        curl.setopt(curl.HTTPHEADER, ["Expect:"])
+
         curl.setopt(curl.TCP_NODELAY, True)
         curl.setopt(curl.PROTOCOLS, curl.PROTO_HTTP)
         curl.setopt(curl.USERAGENT, 'RhodeCode HTTP {}'.format(rhodecode.__version__))
         curl.setopt(curl.SSL_VERIFYPEER, 0)
         curl.setopt(curl.SSL_VERIFYHOST, 0)
         self._curl = curl
 
-    def post(self, url, data, allow_redirects=False):
+    def post(self, url, data, allow_redirects=False, headers=None):
+        headers = headers or {}
+        # format is ['header_name1: header_value1', 'header_name2: header_value2'])
+        headers_list = ["Expect:"] + ['{}: {}'.format(k, v) for k, v in headers.items()]
         response_buffer = StringIO()
 
         curl = self._curl
         curl.setopt(curl.URL, url)
         curl.setopt(curl.POST, True)
         curl.setopt(curl.POSTFIELDS, data)
         curl.setopt(curl.FOLLOWLOCATION, allow_redirects)
         curl.setopt(curl.WRITEDATA, response_buffer)
+        curl.setopt(curl.HTTPHEADER, headers_list)
         curl.perform()
 
         status_code = curl.getinfo(pycurl.HTTP_CODE)
 
         return CurlResponse(response_buffer, status_code)
 
 
 class CurlResponse(object):
     """
     The response of a request, modeled after the requests API.
 
     This class provides a subset of the response interface known from the
     library `requests`. It is intentionally kept similar, so that we can use
     `requests` as a drop in replacement for benchmarking purposes.
     """
 
     def __init__(self, response_buffer, status_code):
         self._response_buffer = response_buffer
         self._status_code = status_code
 
     @property
     def content(self):
         try:
             return self._response_buffer.getvalue()
         finally:
             self._response_buffer.close()
 
     @property
     def status_code(self):
         return self._status_code
 
     def iter_content(self, chunk_size):
         self._response_buffer.seek(0)
         while 1:
             chunk = self._response_buffer.read(chunk_size)
             if not chunk:
                 break
             yield chunk
 
 
 def _create_http_rpc_session():
     session = CurlSession()
     return session

rhodecode/lib/vcs/client_http.py

@@ -1,396 +1,408 b''
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2016-2020 RhodeCode GmbH
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License, version 3
 # (only), as published by the Free Software Foundation.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 # This program is dual-licensed. If you wish to learn more about the
 # RhodeCode Enterprise Edition, including its added features, Support services,
 # and proprietary license terms, please see https://rhodecode.com/licenses/
 
 """
 Client for the VCSServer implemented based on HTTP.
 """
 
 import copy
 import logging
 import threading
 import time
 import urllib2
 import urlparse
 import uuid
 import traceback
 
 import pycurl
 import msgpack
 import requests
 from requests.packages.urllib3.util.retry import Retry
 
 import rhodecode
 from rhodecode.lib import rc_cache
 from rhodecode.lib.rc_cache.utils import compute_key_from_params
 from rhodecode.lib.system_info import get_cert_path
 from rhodecode.lib.vcs import exceptions, CurlSession
 from rhodecode.lib.utils2 import str2bool
 
 log = logging.getLogger(__name__)
 
 
 # TODO: mikhail: Keep it in sync with vcsserver's
 # HTTPApplication.ALLOWED_EXCEPTIONS
 EXCEPTIONS_MAP = {
     'KeyError': KeyError,
     'URLError': urllib2.URLError,
 }
 
 
 def _remote_call(url, payload, exceptions_map, session):
     try:
-        response = session.post(url, data=msgpack.packb(payload))
+        headers = {
+            'X-RC-Method': payload.get('method'),
+            'X-RC-Repo-Name': payload.get('_repo_name')
+        }
+        response = session.post(url, data=msgpack.packb(payload), headers=headers)
     except pycurl.error as e:
         msg = '{}. \npycurl traceback: {}'.format(e, traceback.format_exc())
         raise exceptions.HttpVCSCommunicationError(msg)
     except Exception as e:
         message = getattr(e, 'message', '')
         if 'Failed to connect' in message:
             # gevent doesn't return proper pycurl errors
             raise exceptions.HttpVCSCommunicationError(e)
         else:
             raise
 
     if response.status_code >= 400:
         log.error('Call to %s returned non 200 HTTP code: %s',
                   url, response.status_code)
         raise exceptions.HttpVCSCommunicationError(repr(response.content))
 
     try:
         response = msgpack.unpackb(response.content)
     except Exception:
         log.exception('Failed to decode response %r', response.content)
         raise
 
     error = response.get('error')
     if error:
         type_ = error.get('type', 'Exception')
         exc = exceptions_map.get(type_, Exception)
         exc = exc(error.get('message'))
         try:
             exc._vcs_kind = error['_vcs_kind']
         except KeyError:
             pass
 
         try:
             exc._vcs_server_traceback = error['traceback']
             exc._vcs_server_org_exc_name = error['org_exc']
             exc._vcs_server_org_exc_tb = error['org_exc_tb']
         except KeyError:
             pass
 
         raise exc
     return response.get('result')
 
 
 def _streaming_remote_call(url, payload, exceptions_map, session, chunk_size):
     try:
         response = session.post(url, data=msgpack.packb(payload))
     except pycurl.error as e:
         msg = '{}. \npycurl traceback: {}'.format(e, traceback.format_exc())
         raise exceptions.HttpVCSCommunicationError(msg)
     except Exception as e:
         message = getattr(e, 'message', '')
         if 'Failed to connect' in message:
             # gevent doesn't return proper pycurl errors
             raise exceptions.HttpVCSCommunicationError(e)
         else:
             raise
 
     if response.status_code >= 400:
         log.error('Call to %s returned non 200 HTTP code: %s',
                   url, response.status_code)
         raise exceptions.HttpVCSCommunicationError(repr(response.content))
 
     return response.iter_content(chunk_size=chunk_size)
 
 
 class ServiceConnection(object):
     def __init__(self, server_and_port, backend_endpoint, session_factory):
         self.url = urlparse.urljoin('http://%s' % server_and_port, backend_endpoint)
         self._session_factory = session_factory
 
     def __getattr__(self, name):
         def f(*args, **kwargs):
             return self._call(name, *args, **kwargs)
         return f
 
     @exceptions.map_vcs_exceptions
     def _call(self, name, *args, **kwargs):
         payload = {
             'id': str(uuid.uuid4()),
             'method': name,
             'params': {'args': args, 'kwargs': kwargs}
         }
         return _remote_call(
             self.url, payload, EXCEPTIONS_MAP, self._session_factory())
 
 
 class RemoteVCSMaker(object):
 
     def __init__(self, server_and_port, backend_endpoint, backend_type, session_factory):
         self.url = urlparse.urljoin('http://%s' % server_and_port, backend_endpoint)
         self.stream_url = urlparse.urljoin('http://%s' % server_and_port, backend_endpoint+'/stream')
 
         self._session_factory = session_factory
         self.backend_type = backend_type
 
     @classmethod
     def init_cache_region(cls, repo_id):
         cache_namespace_uid = 'cache_repo.{}'.format(repo_id)
         region = rc_cache.get_or_create_region('cache_repo', cache_namespace_uid)
         return region, cache_namespace_uid
 
     def __call__(self, path, repo_id, config, with_wire=None):
         log.debug('%s RepoMaker call on %s', self.backend_type.upper(), path)
         return RemoteRepo(path, repo_id, config, self, with_wire=with_wire)
 
     def __getattr__(self, name):
         def remote_attr(*args, **kwargs):
             return self._call(name, *args, **kwargs)
         return remote_attr
 
     @exceptions.map_vcs_exceptions
     def _call(self, func_name, *args, **kwargs):
         payload = {
             'id': str(uuid.uuid4()),
             'method': func_name,
             'backend': self.backend_type,
             'params': {'args': args, 'kwargs': kwargs}
         }
         url = self.url
         return _remote_call(url, payload, EXCEPTIONS_MAP, self._session_factory())
 
 
 class RemoteRepo(object):
     CHUNK_SIZE = 16384
 
     def __init__(self, path, repo_id, config, remote_maker, with_wire=None):
         self.url = remote_maker.url
         self.stream_url = remote_maker.stream_url
         self._session = remote_maker._session_factory()
 
         cache_repo_id = self._repo_id_sanitizer(repo_id)
+        _repo_name = self._get_repo_name(config, path)
         self._cache_region, self._cache_namespace = \
             remote_maker.init_cache_region(cache_repo_id)
 
         with_wire = with_wire or {}
 
         repo_state_uid = with_wire.get('repo_state_uid') or 'state'
+
         self._wire = {
+            "_repo_name": _repo_name,
             "path": path,  # repo path
             "repo_id": repo_id,
             "cache_repo_id": cache_repo_id,
             "config": config,
             "repo_state_uid": repo_state_uid,
             "context": self._create_vcs_cache_context(path, repo_state_uid)
         }
 
         if with_wire:
             self._wire.update(with_wire)
 
         # NOTE(johbo): Trading complexity for performance. Avoiding the call to
         # log.debug brings a few percent gain even if is is not active.
         if log.isEnabledFor(logging.DEBUG):
             self._call_with_logging = True
 
         self.cert_dir = get_cert_path(rhodecode.CONFIG.get('__file__'))
 
+    def _get_repo_name(self, config, path):
+        repo_store = config.get('paths', '/')
+        return path.split(repo_store)[-1].lstrip('/')
+
     def _repo_id_sanitizer(self, repo_id):
         pathless = repo_id.replace('/', '__').replace('-', '_')
         return ''.join(char if ord(char) < 128 else '_{}_'.format(ord(char)) for char in pathless)
 
     def __getattr__(self, name):
 
         if name.startswith('stream:'):
             def repo_remote_attr(*args, **kwargs):
                 return self._call_stream(name, *args, **kwargs)
         else:
             def repo_remote_attr(*args, **kwargs):
                 return self._call(name, *args, **kwargs)
 
         return repo_remote_attr
 
     def _base_call(self, name, *args, **kwargs):
         # TODO: oliver: This is currently necessary pre-call since the
         # config object is being changed for hooking scenarios
         wire = copy.deepcopy(self._wire)
         wire["config"] = wire["config"].serialize()
         wire["config"].append(('vcs', 'ssl_dir', self.cert_dir))
 
         payload = {
             'id': str(uuid.uuid4()),
             'method': name,
+            "_repo_name":  wire['_repo_name'],
             'params': {'wire': wire, 'args': args, 'kwargs': kwargs}
         }
 
         context_uid = wire.get('context')
         return context_uid, payload
 
     def get_local_cache(self, name, args):
         cache_on = False
         cache_key = ''
         local_cache_on = str2bool(rhodecode.CONFIG.get('vcs.methods.cache'))
 
         cache_methods = [
             'branches', 'tags', 'bookmarks',
             'is_large_file', 'is_binary',
             'fctx_size', 'stream:fctx_node_data', 'blob_raw_length',
             'node_history',
             'revision', 'tree_items',
             'ctx_list', 'ctx_branch', 'ctx_description',
             'bulk_request',
             'assert_correct_path'
         ]
 
         if local_cache_on and name in cache_methods:
             cache_on = True
             repo_state_uid = self._wire['repo_state_uid']
             call_args = [a for a in args]
             cache_key = compute_key_from_params(repo_state_uid, name, *call_args)
 
         return cache_on, cache_key
 
     @exceptions.map_vcs_exceptions
     def _call(self, name, *args, **kwargs):
         context_uid, payload = self._base_call(name, *args, **kwargs)
         url = self.url
 
         start = time.time()
         cache_on, cache_key = self.get_local_cache(name, args)
 
         @self._cache_region.conditional_cache_on_arguments(
             namespace=self._cache_namespace, condition=cache_on and cache_key)
         def remote_call(_cache_key):
             if self._call_with_logging:
                 log.debug('Calling %s@%s with args:%.10240r. wire_context: %s cache_on: %s',
                           url, name, args, context_uid, cache_on)
             return _remote_call(url, payload, EXCEPTIONS_MAP, self._session)
 
         result = remote_call(cache_key)
         if self._call_with_logging:
             log.debug('Call %s@%s took: %.4fs. wire_context: %s',
                       url, name, time.time()-start, context_uid)
         return result
 
     @exceptions.map_vcs_exceptions
     def _call_stream(self, name, *args, **kwargs):
         context_uid, payload = self._base_call(name, *args, **kwargs)
         payload['chunk_size'] = self.CHUNK_SIZE
         url = self.stream_url
 
         start = time.time()
         cache_on, cache_key = self.get_local_cache(name, args)
 
         # Cache is a problem because this is a stream
         def streaming_remote_call(_cache_key):
             if self._call_with_logging:
                 log.debug('Calling %s@%s with args:%.10240r. wire_context: %s cache_on: %s',
                           url, name, args, context_uid, cache_on)
             return _streaming_remote_call(url, payload, EXCEPTIONS_MAP, self._session, self.CHUNK_SIZE)
 
         result = streaming_remote_call(cache_key)
         if self._call_with_logging:
             log.debug('Call %s@%s took: %.4fs. wire_context: %s',
                       url, name, time.time()-start, context_uid)
         return result
 
     def __getitem__(self, key):
         return self.revision(key)
 
     def _create_vcs_cache_context(self, *args):
         """
         Creates a unique string which is passed to the VCSServer on every
         remote call. It is used as cache key in the VCSServer.
         """
         hash_key = '-'.join(map(str, args))
         return str(uuid.uuid5(uuid.NAMESPACE_URL, hash_key))
 
     def invalidate_vcs_cache(self):
         """
         This invalidates the context which is sent to the VCSServer on every
         call to a remote method. It forces the VCSServer to create a fresh
         repository instance on the next call to a remote method.
         """
         self._wire['context'] = str(uuid.uuid4())
 
 
 class VcsHttpProxy(object):
 
     CHUNK_SIZE = 16384
 
     def __init__(self, server_and_port, backend_endpoint):
         retries = Retry(total=5, connect=None, read=None, redirect=None)
 
         adapter = requests.adapters.HTTPAdapter(max_retries=retries)
         self.base_url = urlparse.urljoin('http://%s' % server_and_port, backend_endpoint)
         self.session = requests.Session()
         self.session.mount('http://', adapter)
 
     def handle(self, environment, input_data, *args, **kwargs):
         data = {
             'environment': environment,
             'input_data': input_data,
             'args': args,
             'kwargs': kwargs
         }
         result = self.session.post(
             self.base_url, msgpack.packb(data), stream=True)
         return self._get_result(result)
 
     def _deserialize_and_raise(self, error):
         exception = Exception(error['message'])
         try:
             exception._vcs_kind = error['_vcs_kind']
         except KeyError:
             pass
         raise exception
 
     def _iterate(self, result):
         unpacker = msgpack.Unpacker()
         for line in result.iter_content(chunk_size=self.CHUNK_SIZE):
             unpacker.feed(line)
             for chunk in unpacker:
                 yield chunk
 
     def _get_result(self, result):
         iterator = self._iterate(result)
         error = iterator.next()
         if error:
             self._deserialize_and_raise(error)
 
         status = iterator.next()
         headers = iterator.next()
 
         return iterator, status, headers
 
 
 class ThreadlocalSessionFactory(object):
     """
     Creates one CurlSession per thread on demand.
     """
 
     def __init__(self):
         self._thread_local = threading.local()
 
     def __call__(self):
         if not hasattr(self._thread_local, 'curl_session'):
             self._thread_local.curl_session = CurlSession()
         return self._thread_local.curl_session

rhodecode/tests/vcs/test_client_http.py

@@ -1,133 +1,135 b''
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License, version 3
 # (only), as published by the Free Software Foundation.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 # This program is dual-licensed. If you wish to learn more about the
 # RhodeCode Enterprise Edition, including its added features, Support services,
 # and proprietary license terms, please see https://rhodecode.com/licenses/
 
 import logging
 
 import mock
 import msgpack
 import pytest
 
 from rhodecode.lib import vcs
 from rhodecode.lib.vcs import client_http, exceptions
 
 
 def is_new_connection(logger, level, message):
     return (
         logger == 'requests.packages.urllib3.connectionpool' and
         message.startswith('Starting new HTTP'))
 
 
 @pytest.fixture()
 def stub_session():
     """
     Stub of `requests.Session()`.
     """
     session = mock.Mock()
     post = session.post()
     post.content = msgpack.packb({})
     post.status_code = 200
 
     session.reset_mock()
     return session
 
 
 @pytest.fixture()
 def stub_fail_session():
     """
     Stub of `requests.Session()`.
     """
     session = mock.Mock()
     post = session.post()
     post.content = msgpack.packb({'error': '500'})
     post.status_code = 500
 
     session.reset_mock()
     return session
 
 
 @pytest.fixture()
 def stub_session_factory(stub_session):
     """
     Stub of `rhodecode.lib.vcs.client_http.ThreadlocalSessionFactory`.
     """
     session_factory = mock.Mock()
     session_factory.return_value = stub_session
     return session_factory
 
 
 @pytest.fixture()
 def stub_session_failing_factory(stub_fail_session):
     """
     Stub of `rhodecode.lib.vcs.client_http.ThreadlocalSessionFactory`.
     """
     session_factory = mock.Mock()
     session_factory.return_value = stub_fail_session
     return session_factory
 
 
 def test_uses_persistent_http_connections(caplog, vcsbackend_hg):
     repo = vcsbackend_hg.repo
     remote_call = repo._remote.branches
 
     with caplog.at_level(logging.INFO):
         for x in range(5):
             remote_call(normal=True, closed=False)
 
     new_connections = [
         r for r in caplog.record_tuples if is_new_connection(*r)]
     assert len(new_connections) <= 1
 
 
 def test_repo_maker_uses_session_for_classmethods(stub_session_factory):
     repo_maker = client_http.RemoteVCSMaker(
         'server_and_port', 'endpoint', 'test_dummy_scm', stub_session_factory)
     repo_maker.example_call()
     stub_session_factory().post.assert_called_with(
-        'http://server_and_port/endpoint', data=mock.ANY)
+        'http://server_and_port/endpoint', data=mock.ANY,
+        headers={'X-RC-Method': 'example_call', 'X-RC-Repo-Name': None})
 
 
 def test_repo_maker_uses_session_for_instance_methods(
         stub_session_factory, config):
     repo_maker = client_http.RemoteVCSMaker(
         'server_and_port', 'endpoint', 'test_dummy_scm', stub_session_factory)
     repo = repo_maker('stub_path', 'stub_repo_id', config)
     repo.example_call()
     stub_session_factory().post.assert_called_with(
-        'http://server_and_port/endpoint', data=mock.ANY)
+        'http://server_and_port/endpoint', data=mock.ANY,
+        headers={'X-RC-Method': 'example_call', 'X-RC-Repo-Name': 'stub_path'})
 
 
 @mock.patch('rhodecode.lib.vcs.client_http.ThreadlocalSessionFactory')
 @mock.patch('rhodecode.lib.vcs.connection')
 def test_connect_passes_in_the_same_session(
         connection, session_factory_class, stub_session):
     session_factory = session_factory_class.return_value
     session_factory.return_value = stub_session
 
     vcs.connect_http('server_and_port')
 
 
 def test_repo_maker_uses_session_that_throws_error(
         stub_session_failing_factory, config):
     repo_maker = client_http.RemoteVCSMaker(
         'server_and_port', 'endpoint', 'test_dummy_scm', stub_session_failing_factory)
     repo = repo_maker('stub_path', 'stub_repo_id', config)
 
     with pytest.raises(exceptions.HttpVCSCommunicationError):
         repo.example_call()