View the original community article here
Last tested: Jan 10, 2019
When you have an issue with API authentication and received the following error message, it is likely the URL is not set properly in API host URL setting. Therefore it is better to ask your instance Admin to check it with the following step first.
• Error message
Failed to establish a new connection: [Errno 8] nodename nor servname provided, or not known',))
• Check Step
- Click Admin.
- Click API and check whether the URL in "API host URL " is same as the one that the user is using. If it is different, ask the Admin to set the correct URL.
Note: The API host URL should specify the hostname and port that a client on the public internet should use to connect to the Looker instance on the API service port. If the Looker instance is behind a firewall, proxy, or load balancer, the name of the Looker instance ("inside" the firewall) may not match the "public name" that clients must use "outside" the firewall. There is no reliable way for the Looker instance to figure this out when it is behind a proxy server. Make sure your instance Admin is aware of your network configuration and whether the "public" name to reach the Looker instance is different from the Looker instance's machine name on the local LAN.
When there is a firewall, proxy, or load balancer in front of an on-prem Looker instance, the user's network IT admin will need to configure your firewall/proxy/load balancer to forward a port to the Looker instance's API web service port, default 19999. For hosted lookers, this will be taken care of automatically by Looker Ops provisioning.
<Example: If the instance is using "aaaaa.looker.com">
Note: Changing the API Host URL DOES NOT change the hostname of the Looker instance nor the port that the Looker API web service listens to. This input box merely informs Looker of the PUBLIC FACING name and port that clients must use to connect to the Looker instance through the firewall/proxy/load balancer. Looker will insert this API Host URL into the API metadata so that clients reading the metadata will know how to connect to the Looker API.