Unable to connect to my cosmos mongo db from Azure web app after enabling pvt endpoints and vnet integration

I have a web app (linux) where i push my docker image via container registry which connects to the cosmos mongo database.

It works fine when eveyrthing is via public network.

When i enable private endpoints and vnet integration , my app works fine but it fails to communicate to the database.

From the same vnet, if i do nslookup from a VM to db it works indicating no issues with private endpoints

My error is:-

pymongo.errors.ServerSelectionTimeoutError:xxx.mongocluster.cosmos.azure.com:27017: [Errno -3] Temporary failure in name resolution (configured timeouts: socketTimeoutMS: 20000.0ms, connectTimeoutMS: 20000.0ms), Timeout: 30s, Topology Description:

UJTyagi-MSFT 230 Reputation points Microsoft Employee

2024-06-13T07:25:12.22+00:00
Hi DangShubhamADVDAADASSPLTTE1DT7-7504,

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

Regarding your issue kindly correct me if my understanding is correct.

You are using an Azure Web App which has Vnet integration with Vnet let's assume VnetA. You are using a private endpoint for cosmos mongo database which is having private link from the same Vnet VnetA.

When your resolve the xxx.mongocluster.cosmos.azure.com from VM which is from the same VnetA it resolves correctly to the private ip address of cosmos mongo database.

However, you are getting the below error while accessing cosmos mongo database from Web app when Vnet integration for Web App and private Endpoint for cosmos mongo database is enabled.

Temporary failure in name resolution (configured timeouts: socketTimeoutMS: 20000.0ms, connectTimeoutMS: 20000.0ms), Timeout: 30s, Topology Description:

If the above statement is correct Kindly launch the Kudu console from your webapp. Refer the below link -

https://video2.skills-academy.com/en-us/azure/app-service/resources-kudu

From Kudu console kindly run the below command and share the output -

Curl -L -v xxx.mongocluster.cosmos.azure.com And tcpping xxx.mongocluster.cosmos.azure.com:<port>

Kindly post the output of the commands and based on the output we can decide the next plan of action.

Regards

Ujjawal Tyagi
DangShubhamADVDAADASSPLTTE1DT7-7504 0 Reputation points

2024-06-13T09:16:30.09+00:00
Thanks for the reply.

Curl Command O/P from web app:-

Could not resolve host: xxx.mongocluster.cosmos.azure.com

Closing connection 0

curl: (6) Could not resolve host: xxx.mongocluster.cosmos.azure.com

While tcpping command does not consoles anything for me

Curl Command O/p from VM:-

Host c.xxx.mongocluster.cosmos.azure.com:80 was resolved.

IPv6: (none)

IPv4: 10.xx.xx218

connect to 10.xx.xx.218 port 80 from 0.0.0.0 port 63893 failed: Timed out

Failed to connect to c.xx.mongocluster.cosmos.azure.com port 80 after 21154 ms: Couldn't connect to server

Closing connection
UJTyagi-MSFT 230 Reputation points Microsoft Employee

2024-06-13T11:32:29.2+00:00

Hi DangShubhamADVDAADASSPLTTE1DT7-7504,

Kindly validate the NSG Outbound rules enforced on the subnet used for the vnet Intergration with webapp and NSG inbound rules enforced on the subnet used for Private link for Mongo cosmos cluster. It seems there is connectivity issue as well.

If you need any help with the NSG validation, Kindly Open a support case with Virtual Network Team.

Regards

ujjawal tyagi

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Unable to connect to my cosmos mongo db from Azure web app after enabling pvt endpoints and vnet integration