What does this Python requests error mean?

Question

What does this Python requests error mean? Does this mean it tries to connect to the server and couldn't? What does [Errno 8] nodename nor servname provided, or not known mean?

File "python2.7/site-packages/requests/api.py", line 55, in get

File "python2.7/site-packages/requests/api.py", line 44, in request

File "python2.7/site-packages/requests/sessions.py", line 279, in request

File "python2.7/site-packages/requests/sessions.py", line 374, in send

File "python2.7/site-packages/requests/adapters.py", line 209, in send

ConnectionError: HTTPConnectionPool(host='localhost', port=8091): Max retries exceeded with url: /pools/default (Caused by : [Errno 8] nodename nor servname provided, or not known

The code generated this: http://github.com...

class RestConnection(object):
    def __init__(self, serverInfo):
        #serverInfo can be a json object
        if isinstance(serverInfo, dict):
            self.ip = serverInfo["ip"]
            self.username = serverInfo["username"]
            self.password = serverInfo["password"]
            self.port = serverInfo["port"]
            self.couch_api_base = serverInfo.get("couchApiBase")
        else:
            self.ip = serverInfo.ip
            self.username = serverInfo.rest_username
            self.password = serverInfo.rest_password
            self.port = serverInfo.port
            self.couch_api_base = None

        self.base_url = "http://{0}:{1}".format(self.ip, self.port)
        server_config_uri = ''.join([self.base_url, '/pools/default'])
        self.config = requests.get(server_config_uri).json()
        # if couchApiBase is not set earlier, let's look it up
        if self.couch_api_base is None:
            #couchApiBase is not in node config before Couchbase Server 2.0
            self.couch_api_base = self.config["nodes"][0].get("couchApiBase")

FYI, This error is generated from the Couchbase Python client.

Answer 1

It means the DNS lookup of the host name you're trying to access failed. For example, I get the same error if I try to look up an invalid host name:

>>> import requests
>>> requests.get('http://apsoapsodjaopisjdaoij.com')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/requests/api.py", line 65, in get
    return request('get', url, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/requests/safe_mode.py", line 39, in wrapped
    return function(method, url, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/requests/api.py", line 51, in request
    return session.request(method=method, url=url, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/requests/sessions.py", line 241, in request
    r.send(prefetch=prefetch)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/requests/models.py", line 631, in send
    raise ConnectionError(sockerr)
requests.exceptions.ConnectionError: [Errno 8] nodename nor servname provided, or not known

Check the value of serverInfo["ip"] and make sure it's set correctly.

Answer 2

Adding my own experience for those who are experiencing this in the future.

It turns out that this was actually because I had reach the maximum number of open files on my system. It had nothing to do with failed connections, or even a DNS error as indicated.