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

Nasir Siddiqui 0

I am having a weird issue with the website configure on Azure Application gateway , website is down for almost 3 hours and when I checked Azure Application gateway monitoring graphs they all are showing dotted lines for that time range and data is not available, also log analytics workspace is not showing any data in access logs and performance logs during that time period.

We are using Cloudflare DNS with proxy enabled. Can anyone faced such type of issue before or provide any help in this regard ?

Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-09-19T05:54:04.2933333+00:00
Hi @Nasir Siddiqui ,

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

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.

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://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshooting#how-to-check-backend-health

For your reference: https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshooting#overview

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://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-diagnostics#:~:text=Application%20Gateway%20logs,this%20raw%20data.

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://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-diagnostics#:~:text=Application%20Gateway%20logs,this%20raw%20data.

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://learn.microsoft.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.
Nasir Siddiqui 0 Reputation points

2024-09-19T12:16:43.4966667+00:00

Thanks Sai for the prompt response, but during the downtime , all backend instances are healthy and web server was running on them, also the diagnostic settings is already enabled and Log analytics configured with it and the Access logs and Performance logs data also missing for that period of time. Thats why I am unable to find the root cause for the issue , Azure service health also showing OK for App Gateway service
Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-09-20T06:41:41.7233333+00:00
Hi @Nasir Siddiqui ,

Hope you are having a great day!

Before proceeding, please provide the below information so that we could assist you better.

Could you please tell us the region of the App Gateway?

When you mention “Website is down,” could you clarify the nature of the issue? Was it a server error (5XX), a client error (4XX), a DNS failure, or something else? Please provide the specific error encountered during the incident.

Thanks,

Sai Prasanna.
Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-09-23T01:01:09.25+00:00

Hi @Nasir Siddiqui ,

Hope you are having a great day.

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, please respond with more details and we will try to help.

Your contribution is highly appreciated.

Thanks.
Nasir Siddiqui 0 Reputation points

2024-09-23T13:18:12.5633333+00:00

Hi @Sai Prasanna Sinde (Quadrant Resource LLC) ,

We were getting Error 522 gateway timeout as we are using cloudflare DNS and the region is East US and we are using application gateway v1 with Medium SKU.

The downtime was 3 hours and 38 minutes (10:40 AM to 02:19 pm UTC 17th September)
Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-09-26T04:40:55.8133333+00:00

Hi @Nasir Siddiqui ,

Hope you are having a great day.

Following up to see if the above suggestion was helpful. And, if you have any further query do let us know.

Thanks.
Nasir Siddiqui 0 Reputation points

2024-09-26T14:55:01.67+00:00

Hi @Sai Prasanna Sinde (Quadrant Resource LLC)

Thanks for your response. Sure , we can connect on a session and I can show the issue that we faced on September 17th. We are not using the technical support plan right now and the subscription is not being managed by CSP
Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-09-27T06:49:55.8233333+00:00

Hi @Nasir Siddiqui ,

Thanks for the reply.

Please check the private messages.

Thanks,

Sai Prasanna.
Nasir Siddiqui 0 Reputation points

2024-09-27T14:45:38.55+00:00

Thank you @Sai Prasanna Sinde (Quadrant Resource LLC) for all your support , I have checked and responded on the private message
Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-10-04T02:22:40.4633333+00:00

Hi @Nasir Siddiqui,Hope you are having a great day!

I have converted my comment into an answer.

If you feel your issue is resolved, please do click **Accept Answer** and **Yes** for was this answer helpful. This will help us and others in the community to find the right answers.

Your contribution is highly appreciated.

And, if you have any further query do let us know.

Thanks,

Sai Prasanna.

1 answer

Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-09-24T17:23:18.02+00:00

Hi @Nasir Siddiqui ,

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

To troubleshoot further, we will need a specialized 1:1 session, where a support engineer can have a screen share session to resolve your issue. If you have a support plan you may file a support ticket, else please do let us know, we will try and help you get a one-time free technical support.

P.S : We will be able to provide you one-time support if and only if your subscription is not managed by a CSP.

Thanks,

Sai Prasanna.
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Sai Prasanna Sinde (Quadrant Resource LLC) 425 Reputation points Microsoft Vendor

2024-10-08T10:09:22.49+00:00

Hi @Nasir Siddiqui,

Hope you are having a great day!

I have converted my comment into an answer.

If you feel your issue is resolved, please do click **Accept Answer** and **Yes** for was this answer helpful. This will help us and others in the community to find the right answers.

Your contribution is highly appreciated.

Thanks,

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

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