When you set up your Application Gateway on Azure, and you’re getting the following message…
Then you know you are in a world of pain in order to debug this. So before we continue, please help to avoid this pain by voting on the user voice! 😉
When we take a look at the documentation, then we see how the logic works… Basically it will do a GET of the following url on each node ; http://127.0.0.1:/. The (healthy) response should be a status code between 200 and 399.
Apart from that, once you have created the application gateway. You’re back-end pool will be empty. So the first thing to check is if you’ve already added your nodes.
Example Troubleshooting : Rancher node shown as down
After cursing for a while, I did a network trace to see what was happening. As my host was an Ubuntu (Linux), I used tcpdump ;
tcpdump port 80
As you can see from the output, there is a “401 Unauthorized” error code. We just learned that the response should be between 200 and 399, so we’re 2 short of a good status.
So how to fix this? Let’s create a custom node…
Why change to this?
Because loading the /login/ page will get you a 200 or 304 (depending on the previous sequence). These values reside between 200 and 399, so we’re good!