Every interface to the APIC goes through the REST API - CLI, GUI, Python SDK, etc. When something does not appear to be working properly with the REST API, it can have significant impact on the system as a whole because it is the ONLY interface we have to the APIC. Knowing how to debug and troubleshoot the REST API can be extremely useful.
This document will detail some little known REST API query strings as well as indicate which logs on the APIC can be monitored to see what is going on with the REST API.
REST API Troubleshooting
All REST API queries go through the web server on node. Logs for web server are saved on the specific APIC or nodes that the REST APIC queries are being run against at:
On the APIC:
On fabric nodes:
These logs role over, so if something occurred a while ago you may have to go back in time and look at files that are compressed.
Having the REST API return what was modified by the POST request
You can have POST requests return what was modified rather than an empty imdata post using a rsp-subtree option set to full (it will return the entire modified Mo), modified (it will return only what was modified), or no (the default behavior of returning nothing). This can be useful in cases beyond debugging as well where you need the results of a dynamic configuration. This does have limits though. For example you can not get a full subtree for the polUni Mo for both GET or POST.