An unexpected isssue in EventGrid Callback validation requests

Question

I did spend hours trying to figure out why Cloud Event Webhook validation was ok in one service and failed in other services in Azure.

I was running the exactly the same App as a App Service and Container App.

I found out that the problem was that the request header names have different casings.

WebHook-Request-Callback:

vs.

webhook-request-callback:

I wish they could atleast be consistent within Azure and EventGrid..

Here's a webhook-request-callback to an App Service

OPTIONS /hook2

CLIENT-IP: 51.12.47.159:64196

DISGUISED-HOST: as-clouddebugger-linux-container.azurewebsites.net

Host: as-clouddebugger-linux-container.azurewebsites.net

Max-Forwards: 10

WAS-DEFAULT-HOSTNAME: as-clouddebugger-linux-container.azurewebsites.net

WebHook-Request-Callback: https://rp-swedencentral.eventgrid.azure.net:553/eventsubscriptions/cloudevent-linux-container/validate?id=041F50B3-5A9F-417B-835D-1CDE58F3C6A9&t=2025-01-29T18:53:45.4115525Z&apiVersion=2024-12-15-preview&token=SZUYTGhOMExsrcg3qmStXMhsezj1TCILREWmZCQXVh4%3d

WebHook-Request-Origin: eventgrid.azure.net

X-ARR-LOG-ID: 32916421-23c7-4df7-8024-d1e0a42ea84b

X-ARR-SSL: 2048|256|CN=Microsoft Azure RSA TLS Issuing CA 08, O=Microsoft Corporation, C=US|CN=*.azurewebsites.net, O=Microsoft Corporation, L=Redmond, S=WA, C=US

X-AppService-Proto: https

X-Client-IP: 51.12.47.159

X-Client-Port: 64196

X-Forwarded-TlsVersion: 1.2

X-Original-For: [::ffff:169.254.131.1]:52719

X-Original-Proto: http

X-Original-URL: /hook2

X-SITE-DEPLOYMENT-ID: as-CloudDebugger-Linux-Container

X-WAWS-Unencoded-URL: /hook2

And here is a request to Container AppService-Proto

OPTIONS /hook2

Content-Length: 0

Host: ca-clouddebugger.orangewater-c2f516d4.swedencentral.azurecontainerapps.io

X-Original-For: [::ffff:100.100.0.180]:56784

X-Original-Proto: http

webhook-request-callback: https://rp-swedencentral.eventgrid.azure.net:553/eventsubscriptions/cloudevent-linux-container-app/validate?id=DDAD8472-2717-4624-8661-210F29029BB2&t=2025-01-29T18:57:11.1296364Z&apiVersion=2024-12-15-preview&token=%2fnvnFmnrE5MGmBCutflYlZTU1Ux9f7JakOtnRNyyYUQ%3d

webhook-request-origin: eventgrid.azure.net

x-arr-ssl: true

x-envoy-expected-rq-timeout-ms: 1800000

x-envoy-external-address: 51.12.47.151

x-k8se-app-kind: web

x-k8se-app-name: ca-clouddebugger--9bn4egg

x-k8se-app-namespace: k8se-apps

x-k8se-protocol: http1

x-ms-containerapp-name: ca-clouddebugger

x-ms-containerapp-revision-name: ca-clouddebugger--9bn4egg

x-request-id: 796c0195-690a-4aa8-95ba-705655383419

Answer 1

Hello @Tore Nestenius

Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.

It seems like you were having trouble with Cloud Event Webhook validation in Azure. I understand that you were running the same App as an App Service and Container App, but the request header names had different casings. It can be frustrating when things are not consistent, but I'm here to help you out.

Based on the information you provided, it looks like the issue was with the casing of the "WebHook-Request-Callback" header. In one case, it was capitalized, and in the other case, it was all lowercase. This caused the validation to fail in one service but not in the other.

Unfortunately, there isn't much that can be done about the inconsistency within Azure and EventGrid. However, now that you know what the issue was, you can make sure to use the correct casing for the header in the future.

If you found the response helpful, please click Accept Answer and Yes for the provided answer. This will help other community members with similar issues find the solution more easily.