__init__() got an unexpected keyword argument 'assert_hostname'

[kh2901]

After upgrading to Version 5.1.1 (recent version 4.2.1) the flask app running on below error:

Traceback (most recent call last):
  File "\elasticapm\transport\http.py", line 79, in send
    "POST", url, body=data, headers=self._headers, timeout=self._timeout, preload_content=False
  File "\urllib3\poolmanager.py", line 324, in urlopen
    response = conn.urlopen(method, u.request_uri, **kw)
  File "\elasticapm\instrumentation\packages\base.py", line 136, in call_if_sampling
    return wrapped(*args, **kwargs)
  File "\elasticapm\instrumentation\packages\base.py", line 136, in call_if_sampling
    return wrapped(*args, **kwargs)
  File "\urllib3\connectionpool.py", line 588, in urlopen
    conn = self._get_conn(timeout=pool_timeout)
  File "\urllib3\connectionpool.py", line 248, in _get_conn
    return conn or self._new_conn()
  File "\urllib3\connectionpool.py", line 209, in _new_conn
    strict=self.strict, **self.conn_kw)
  File "\urllib3\connection.py", line 114, in __init__
    _HTTPConnection.__init__(self, *args, **kw)
TypeError: __init__() got an unexpected keyword argument 'assert_hostname'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "\elasticapm\transport\base.py", line 208, in _flush
    self.send(data)
  File "\elasticapm\transport\http.py", line 92, in send
    raise TransportException(message, data, print_trace=print_trace)
elasticapm.transport.base.TransportException: Unable to reach APM Server: __init__() got an unexpected keyword argument 'assert_hostname' (url: http://<apm-server url>:8200/intake/v2/events)

The NO_PROXY env variable is used.

To Reproduce

1. apm.init_app()
2. Running on TransportException

Expected behavior: Connect to apm-server host and add apm data.

Environment (please complete the following information)

• OS: Windows/Linux (Conda environment)
• Python version: 3.6.8
• Framework and version: Flask 1.1.1
• APM Server version: 7.3.0
• Agent version: 5.1.1

Additional context

Add any other context about the problem here.

• Agent config options ELASTIC_APM = { 'SERVICE_NAME': '', 'SERVER_URL': 'http://%s:8200' % ELASTIC_HOST, 'SECRET_TOKEN': '', 'DEBUG': True, 'ENVIRONMENT': 'development', 'VERIFY_SERVER_CERT': False, 'SERVICE_VERSION': app_version }
• requirements.txt: aniso8601==6.0.0 apispec==2.0.2 asn1crypto==0.24.0 atomicwrites==1.3.0 attrs==19.1.0 blinker==1.4 blueprint==3.4.2 certifi==2019.3.9 cffi==1.12.2 chardet==3.0.4 Click==7.0 colorama==0.4.1 cryptography==2.6.1 ecdsa==0.13 elastic-apm==4.2.1 elasticsearch==7.0.2 Flask==1.1.1 flask-apispec==0.8.1 Flask-JWT==0.3.2 Flask-PyMongo==2.2.0 flask-restplus==0.12.1 future==0.17.1 hvac==0.7.2 idna==2.8 itsdangerous==1.1.0 Jinja2==2.10.1 jsonschema==3.0.1 MarkupSafe==1.1.1 marshmallow==2.19.2 more-itertools==7.0.0 pluggy==0.9.0 psutil==5.6.1 py==1.8.0 pyasn1==0.4.5 pycparser==2.19 PyJWT==1.4.2 pymongo==3.7.2 pyOpenSSL==19.0.0 pyrsistent==0.14.11 pytest==4.4.0 pytest-flask==0.14.0 pytest-mock==1.10.3 python-dateutil==2.8.0 python3-logstash==0.4.80 pytz==2018.9 PyYAML==5.1.1 requests==2.21.0 rsa==4.0 six==1.12.0 urllib3==1.24.1 webargs==5.2.0 Werkzeug==0.15.1 wincertstore==0.2

[basepi]

Looks like we're passing the assert_hostname pieces for cert validation even for http, where certs are definitely not relevant. I'm looking into it.

[basepi]

Ah, I think I see the problem. Can you try removing your 'VERIFY_SERVER_CERT': False, config? I think the issue you're seeing is due to combining https config values with an http SERVER_URL. If removing that config value fixes the error, then it's still a bug but I can verify that I've diagnosed the issue correctly.

[basepi]

(I also have a sneaking suspicion that this error would be present in 4.2.1, but that your prod 4.2.1 instance is using https, while this development instance is using http. Basically, I think this is an old bug triggered by a new config change, not a new bug in the new version. Still good to get it fixed!)

[kh2901]

Ah, I think I see the problem. Can you try removing your 'VERIFY_SERVER_CERT': False, config? I think the issue you're seeing is due to combining https config values with an http SERVER_URL. If removing that config value fixes the error, then it's still a bug but I can verify that I've diagnosed the issue correctly.

@basepi Thank you this fixed the problem.

[basepi]

Awesome! The linked PR will also fix this so you won't have to worry about it in the future.