Azure Functions does not work if length of the request URL (with query-params) is > 2102

I use proxies for a SPA, and to handle OAuth2 authorization code grant flow. When my function app receives a redirect with the code, state, and id_token query params, I was noticing that the function wouldn’t even execute. There is no error in the logs either. So I tested by truncating the value of the query params and it turns out that if the length exceeds 2102, then the routing doesn’t work for some reason.

Investigative information

Note: I have provided information of a normal execution of my function. When the problem occurs, there is actually nothing in the logs that would indicate this problem. Furthermore, Proxy-Trace-Enabled header attribute doesn’t help either because no function has executed.

• Timestamp: 2018-01-19T05:42:29.349
• Function App version (1.0 or 2.0-beta): 1.0
• Function App name:
• Function name(s) (as appropriate): after-auth
• Invocation ID: a3df31ab-6fff-4517-b836-7170e245d1bd
• Region: West US

Repro steps

1. Create a proxy rule that invokes a function.
2. Call the function app so that the proxy rule is executed but with query-params with length > 2102.

Expected behavior

After step 2, the proxy rule would be invoked and the function should execute.

Actual behavior

• Browser receives a 404 Not Found HTTP status code.
• Proxy rule won’t be executed but instead you will get a response The resource you are looking for has been removed, had its name changed, or is temporarily unavailable.

Known workarounds

Use the request body instead of query-params.

Related information

• JS function
• HttpBinding

EDIT: I wanted to clarify that the length I am talking about is the total length of the URL with the query params, and not just the length of the query params put together. EDIT2: Updated the notes under Actual Behavior.

[safihamid]

@praneetloke I tested this again on a new function app and it’s working for me. can you please send me your function app name, proxies.json and the url your are using? you can email me directly at hamids at microsoft dot com

[safihamid]

Yes it will land in v1.0