Unable to connect to Azure Cosmos DB (Mongo vCore cluster).

Question

Unable to connect to Azure Cosmos DB (Mongo vCore cluster).

Animesh 0

Issue: - Connection fails from mongosh, MongoDB Compass, and Node.js app - Error: "error connecting to server" - Issue is reproducible across multiple users and environments - It was working earlier, recently stopped Observations: - Cluster status currently shows "Updating" - Public network access is enabled - Firewall is open Request: - Does "Updating" state block client connections? - How long does update typically take? - How to verify cluster health and readiness?

Nikhil Duserla 9,690 Reputation points Microsoft External Staff Moderator

2026-04-25T11:47:39.3+00:00
Hello @Animesh ,

Hey Animesh, it looks like your Mongo-vCore cluster is in an “Updating” state, which is likely why all your clients (mongosh, Compass, Node.js app) are suddenly unable to connect. Here’s what’s going on and what you can do:

Does “Updating” block client connections?

Yes. While Cosmos DB is applying a configuration change or patch (you’ll see “Updating” in the portal), the data-plane endpoints are briefly taken offline, so new connections will fail until the update completes.

How long does an update typically take?

It depends on what’s being updated (minor patch vs. scaling operations) and the size of your cluster, but most updates finish in 10–30 minutes. In rare cases (large scale-up/down or multi-region config changes) it can stretch up to an hour.

How to verify cluster health and readiness? a. Portal “Overview” blade – wait for “Status: Running” or “Provisioning State: Succeeded.” b. Azure CLI / PowerShell – run a show command: • Azure CLI:
```bash az cosmosdb mongodb cluster show \ --name zeamed-ai-testing \ --resource-group <your-resource-group> ``` Check the “provisioningState” and “connectionState” fields.
• PowerShell:
```powershell Get-AzCosmosDBMongoCluster -ResourceGroupName <RG> -Name zeamed-ai-testing ``` Confirm “ProvisioningState” is “Succeeded.”
c. Diagnostics blade in the portal – run the built-in connectivity checks (firewall, DNS, port reachability). d. Connectivity tests from your client machine once the portal shows “Running”: – DNS resolution:
``` nslookup zeamed-ai-testing.mongocluster.cosmos.azure.com ```
– TCP port:
``` nc -vz zeamed-ai-testing.mongo.cosmos.azure.com 10260 ```

If you’ve been waiting more than an hour or the status never flips back to “Running,” it’s worth opening a support case.

—

Reference docs for more details:

• Troubleshoot connectivity and SDK challenges (Diagnostics, firewall, DNS checks)

https://learn.microsoft.com/azure/cosmos-db/mongodb/vcore/troubleshoot-common-issues

• Firewall and networking configuration for MongoDB vCore

https://learn.microsoft.com/azure/cosmos-db/mongodb/vcore/how-to-public-access

• Using MongoDB shell for connectivity (“authMechanism=SCRAM-SHA-256”, SRV protocol)

https://learn.microsoft.com/azure/cosmos-db/mongodb/vcore/how-to-connect-mongo-shell

• Retrieve and use connection strings (SRV format, encoding)

https://learn.microsoft.com/azure/cosmos-db/mongodb/vcore/tutorial-nodejs-web-app#test-the-mern-application-with-the-azure-cosmos-db-for-mongodb-vcore-cluster

Note: This content was drafted with the help of an AI system. Please verify the information before relying on it for decision-making.
Saraswathi Devadula 16,015 Reputation points Microsoft External Staff Moderator

2026-04-25T14:04:05.1166667+00:00

Hello @Animesh ,

Could you please share the details requested in the private message for further investigation.

1 answer

Your answer

Saraswathi Devadula 16,015 Reputation points Microsoft External Staff Moderator

2026-04-25T14:04:05.1166667+00:00

Hello @Animesh ,

Could you please share the details requested in the private message for further investigation.

Answer 1

Hi ,

Thanks for reaching out to Microsoft Q&A.

Yes, the “Updating” state in Cosmos DB for MongoDB vCore can block or intermittently fail client connections. During this phase, the cluster is undergoing configuration changes (scale, patching, networking, or maintenance), and the service may temporarily reject or drop connections. So your observed “error connecting to server” across mongosh, Compass, and Node.js is consistent with this state.

Update duration is not fixed. In practice, it usually takes 5 to 30 mins for minor changes, but can extend to 45 to 60 mins or more if it involves scaling, storage reconfiguration, or backend maintenance. If it has been stuck beyond an hour, that is a red flag and likely indicates a backend issue.

To verify health and readiness, check the cluster state in the Azure portal until it shows “Running” (not updating). Then validate via connection string using mongosh, check metrics like CPU, connections, and server errors in Azure Monitor, and review Activity Log for recent operations (scale, patch, failover). You can also try a simple ping command (db.runCommand({ ping: 1 })) once status is Running. If it remains in Updating or connections still fail after it returns to Running, escalate to support because vCore clusters can get stuck in a partial update state.

Please 'Upvote'(Thumbs-up) and 'Accept' as answer if the reply was helpful. This will be benefitting other community members who face the same issue.

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Unable to connect to Azure Cosmos DB (Mongo vCore cluster).

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