How Do You Troubleshoot the Error “We are experiencing problems connecting to the Graylog server running on http://127.0.0.1:9000/api”?

Updated on 1/22/19

Problem scenario
You installed Graylog in a Docker container.  You open the URL for the server in a web browser.  You see this message:

" Server currently unavailable

We are experiencing problems connecting to the Graylog server running on http://127.0.0.1:9000/api. Please verify that the server is healthy and working correctly.

You will be automatically redirected to the previous page once we can connect to the server.

Do you need a hand? We can help you."

What should you do?

Solution
1.  Stop the Docker container with Graylog. 
2.  Remove this container. 
3.  Create a new Docker container but replace the 127.0.0.1 with the external IP address of the Linux Docker server (the Docker host).  The command should look like this (but replace x.x.x.x with the IP address of the Linux server):

docker run --link contint-mongo:mongo --link contint-elasticsearch:elasticsearch -p 9000:9000 -e GRAYLOG_WEB_ENDPOINT_URI="http://x.x.x.x:9000/api" -d graylog2/server

4.  If the command you drafted fails, you may need to run it with "sudo " at the beginning.  If you normally need to use sudo before Docker commands, you may want to try to configure your Docker host to not need that; if you need assistance with this, see this posting.