Google Appengine OutBound traffic not going from Custom domain

[Chamika Adikari]

I am setting up a server in google app engine and i have linked a custom domain to it also I can access it from the correct URL. I use this server to issue requests to a third party payment gateway where they whitelist the domain of requests.I cant access it because my requests are not coming from the custom domain i linked to the server . I followed this documentation to map the custom domainhttps://cloud.google.com/appengine/docs/flexible/nodejs/mapping-custom-domains

Is there an additional step to setup outgoing traffic's domain?

[Cristian (Google Cloud Platform Support)]

Hi Chamika,

This is not possible as it has been discussed in the duplicate thread you have created in Stack Overflow [1].

There are already feature requests (like this [1] and this one [2]) on providing static IP for App Engine apps, If you consider the option to have an static IP address for your App Engine Flex application. You may star them for receiving further updates. In the meantime, you may take a look at the workaround provided in Issue 65579021#comment2 [4] or this thread [5] answered by a Product Manager at Google.

[1] https://stackoverflow.com/questions/53976844/google-appengine-outbound-traffic-not-going-from-custom-domain

[2] https://issuetracker.google.com/65579021

[3] https://issuetracker.google.com/35891948

[4] https://issuetracker.google.com/65579021#comment2   

[5] https://stackoverflow.com/questions/36145648/assigning-static-ip-address-to-gae-python-project?answertab=votes#tab-top