In this example, the Gateway Audit Events log contains “Message was not processed: Undefined (-1)”.

There may be some issue with the URL being used to route the request to the backend system. For example, let’s say requests are being routed to http://example.com:12345/sample.

• Protocol: The protocol may need to be HTTP or HTTPS. 
• Hostname: Using nslookup, ensure the host name can be resolved to an IP address. In this example, requests route to www.example.com. If you have access to the server that is producing www.example.com, ensure the www.example.com server is working as expected.
• Port: The port will need to be open on the target system - this usually means checking the web or application server the request is being routed to.
• Context root: The context root, such as /sample, does not always need to match the context root of the service.

If there is an issue with the URL being used to route the requests to the backend application or service, events will not be written to the application server logs, such as SystemOut.log (WebSphere), catalina.log (Tomcat), or mule_ee.log (Mule), as the API Gateway is not able to establish a connection to the application server.

When Auth Method is HTTP Basic (e.g. basic authentication), the user name being used may not be valid.