Azure Application gateway down and monitoring graphs and logs not showing any data

Hi @Nasir Siddiqui ,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

1. The problem with your website on Azure Application Gateway might be due to backend health issues, DNS misconfigurations, or service outages. Dotted lines on monitoring graphs usually mean there's no data or a connection loss. You should check the backend health, verify the DNS settings in Cloudflare, and look at Azure Service Health for any incidents.
2. To resolve the issue, start by checking the health status of your backend pool linked to the Azure Application Gateway. Go to the Azure portal, find your Application Gateway, and look under "Backend Health" to see the status. If all servers in the backend pool are unhealthy, clients will face difficulties accessing the backend application. This can prevent the Application Gateway from forwarding requests, possibly causing downtime.

To verify the backend health: https://video2.skills-academy.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshooting#how-to-check-backend-health

For your reference: https://video2.skills-academy.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshooting#overview

1. The dotted lines in your monitoring graphs show a lack of data during that period. This could be due to backend server unavailability, misconfigurations, or health probe failures. Gaps in data collection might also be related to improperly configured diagnostic settings for your Application Gateway. To address this, you can enable diagnostics to collect logs for Access, Activity, Firewall, and Performance. For your reference: https://video2.skills-academy.com/en-us/azure/application-gateway/application-gateway-diagnostics#:~:text=Application%20Gateway%20logs,this%20raw%20data.
2. Since you're using Cloudflare DNS with proxy enabled, it's crucial to check for any issues with the proxy configuration that might affect accessibility. Make sure your DNS settings are correctly configured and that Cloudflare's IP addresses are whitelisted in your firewall settings. Problems can occur if the origin server isn't responding quickly enough or if firewall rules block access to Cloudflare IPs. To troubleshoot, try disabling the Cloudflare proxy temporarily to see if the website becomes accessible directly. For your reference: https://video2.skills-academy.com/en-us/azure/application-gateway/application-gateway-diagnostics#:~:text=Application%20Gateway%20logs,this%20raw%20data.
3. Finally, set up Azure Monitor alerts to proactively notify you of critical conditions in your monitoring data. This helps you identify and resolve issues before they escalate. Make sure alerts for backend response status, unhealthy host counts, and key integrations are properly configured to provide timely notifications if problems occur again. For your reference: https://video2.skills-academy.com/en-us/azure/application-gateway/configure-alerts-with-templates#:~:text=Azure%20Monitor%20alerts%20proactively,Azure%20Application%20Gateway.

Kindly let us know if the above helps or you need further assistance on this issue.

Thanks,

Sai Prasanna.