Troubleshooting steps to review and try when you're having problems with the Esri Resource Proxy (https://github.com/Esri/resource-proxy)

troubleshooting-esri-resource-proxy.md

Note: In general the below steps are assuming the .NET (.ashx) proxy. Some of the steps may also apply to the Java or PHP proxies.

Proxy is not working

1. Read through the instructions/troubleshooting on both the main proxy page as well as the specific readme for your particular proxy.
2. Try the proxy against a known working url (like http://esri.com) and make sure the page comes back (the page may look weird but as long as you don't get an error and get something back, you know the proxy is at least working for that URL.)
3. Try turning logging off.
4. Test if setting mustMatch to false makes it work. If so, see mustMatch=false works but not when I set to true below.
5. Are there outbound firewall settings on your machine that are preventing the proxy from getting the requests for you? You can test this by remoting into the machine and trying to open the URL you are trying to proxy in a web browser. This can be a problem particularly on AWS where in/outbound firewall rules are by default locked down (configured in the AWS managment console).

mustMatch=false works but not when I set to true

Having this setting set to true for public/production sites is very important for security.

1. Is this happening on all urls or just some of them?
2. Are the URLs in your serverUrl tags exactly (even CAPS) matching the URLs that you're trying to access?
3. What is your matchAll setting?
4. Try doing the proxy request on the VM that the proxy is running on - sometimes IIS will give you better error messaging if you're on the same machine.
5. Are you on the latest, released proxy version? (https://github.com/Esri/resource-proxy/releases)