I have a Sitecore 9.0.2 environment in Azure PaaS. It is connecting to different third party services to get and data. Whenever third party update their system or make any new release our portal goes down or start showing the blank page as data is coming from third party. I want to show a Maintenance page on the site whenever third party is upgrading their environment. Third party in advance provide the time line for their system upgrade.
I tried to create a "app_offline.htm" page but it is not working in Azure PaaS and throwing following exception. "502 - Web server received an invalid response while acting as a gateway or proxy server."
Please help me with this issue.
Thanks in Advance Alok...