Connection being rejected to my Firebase App Hosting instance, only when using my custom domain

[someonecool]

Hi,

I have this SSR app I'm hosting on Firebase App Hosting. It runs fine when I'm running on the browser, both using my custom domain (that I set up via the Firebase App Hosting console), and through the Cloud Run domain.

Though I have a feature that allows users to share the URL via Whatsapp. What happens then is that Whatsapp will fetch my website's content and generate a card with the favicon and title. The problem is that when I try this using my custom domain, it just doesn't work,. WhatsApp is unable to fetch my website's content. It works well when using my Cloud App Run domain, but not my custom domain. This used to work just fine when I was using Vercel to host my app.

There are no logs anywhere in GCP with WhatsApp attempts to fetch my website content. I believe that the load balancer used by Firebase might be blocking this access, and since that instance is hidden under Firebase's implementation detail, I cannot debug what's going on.

What can I do to debug or escalate this?

Thank you

[ronnelg]

Hi @someonecool, 

Welcome to Google Cloud Community!

As I understand, you have an app hosted on Firebase App Hosting. It works fine when run on a browser for both Cloud Run domain and custom domain. As it works already on your browser, I assume that your custom domain was successfully set up and the SSL certificate already provisioned.

Does the issue still exist? Where are you trying to run the WhatsApp that won't fetch your website's content? Is it on your mobile device? Maybe your website is heavily coded with lots of resources and the app cannot load it. Try to create a very basic HTML page and deploy it to your Firebase App Hosting with your custom domain. If this works, the problem is likely with your website's code or resources.

Also, if your website loads over HTTPS but some resources such as images and scripts are loaded over HTTP, WhatsApp will likely block it. Ensure that everything is loaded over HTTPS. WhatsApp sometimes caches content. Try clearing WhatsApp's cache or testing with a fresh install on another device.

For the logs related to Firebase App Hosting, please refer to this Cloud Audit Logging documentation. If the issue still exists, what I recommend is to reach out or file a case to Google Cloud Customer Care for 1:1 technical support as they have the right resources and tools to check and review your project.

Was this helpful? If so, please accept this answer as “Solution”. If you need additional assistance, reply here within 2 business days and I’ll be happy to help.

[someonecool]

Thank you for your response, @ronnelg. Yes, the issue still exists. As far as your suggestion to check for the website content, and/or HTTPS content mixed with HTTP, I don't think that this is influencing the outcome, as if I use my cloud run URL directly instead of my custom domain, everything works just fine.

The issue is really only happening only when using the custom domain. Also, this was working just fine when I had my service being hosted somewhere else.