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I have 2 Vnets :
Vnet1 ="cosmos-db-vnet" with "private_subnet" in which the cosmos-db and its private endpoint are created
Vnet2 ="client-vnet" with "private_subnet" in which the app service and its private endpoint are created and another subnet "subnet_out" for Vnet integration of the app service
I have enabled Vnet peering between the two vnets but my java code running inside the the app service can't connect to the mongo db I get a read timeout
I guess the problem is the app sends traffic through the subnet_out with a certain ip and the cosmos respond at the same
I want some helpful thoughts that I can implement
By peering the networks you allow communication to the Private Endpoint, however to resolve the name you will need to link the Private DNS zone that has your Private Endpoint DNS records in it, to both vNets.
I have created a custom private dns zone for the cosmos db private endpoint's network interface private Ip adress in the client VNet like this
db.clientname.ozone.io with the private IP adress of the cosmos db network interface
and I linked it with client Vnet
this is my connection string :
Hostname="db.clientname.ozone.io";
AppName ="XXXX";
Database="YYY";
DbConnectionString = "mongodb://" + DbUsername + ":" + DbPassword + "@" + Hostname + ":10255/" + Database +"?ssl=false&retrywrites=false&replicaSet=globaldb&authmechanism=SCRAM-SHA-256&appname=@" + AppName + "@";
but whenever I try to connect with my java app that is hosted in the web app I get an error :
exception={com.mongodb.MongoSocketReadTimeoutException: Timeout while receiving message}, caused by {java.net.SocketTimeoutException: Read timed out}}]
At this point I don't know what to do
It seems like you have correctly created a custom private DNS zone for the Cosmos DB private endpoint's network interface private IP address in the client VNet and linked it with the client VNet. However, the error you are getting suggests that there might be an issue with the connection between the app service and Cosmos DB.
Here are a few things you can try to troubleshoot the issue:
Check if the connection string for the app service is using the correct hostname and port number for the private endpoint of Cosmos DB. You can check this by verifying that the hostname and port number in the connection string match the private endpoint of Cosmos DB.
Check if there are any network security groups (NSGs) or route tables that might be blocking traffic between the app service and Cosmos DB.
If you have checked all of the above and are still experiencing issues, you may want to check the logs for both the app service and Cosmos DB to see if there are any errors or timeouts being reported. Additionally, you may want to try increasing the timeout values for the app service to see if that resolves the issue.
Please note part of this answer was generated by OpenAI. If you have further questions or concerns after trying the above suggestions, please reply here so we can assist you further.
You have not correctly created the Private DNS zone. The Private DNS zone for private endpoints for Cosmos, assuming you are using the Mongo interface should be "privatelink.mongo.cosmos.azure.com". If you created the Private Endpoint using the Azure portal then this zone should already have been created for you, you just need to link it to the other network.
@brtrach-MSFT based on the information the user provided, the private DNS zone has not been created correctly and so DNS resolution is still the problem here.