Diagnose and troubleshoot Azure Cosmos DB Java v4 SDK service unavailable exceptions


The Java v4 SDK wasn't able to connect to Azure Cosmos DB.

Troubleshooting steps

The following list contains known causes and solutions for service unavailable exceptions.

The required ports are being blocked

Verify that all the required ports are enabled. If the account is configured with private endpoint, then more ports are required to be opened.

failed to establish connection to {account name}.documents.azure.com/<unresolved>:3044 due to io.netty.channel.ConnectTimeoutException:

Client initialization failure

The following exception is hit if the SDK isn't able to talk to the Azure Cosmos DB instance. This exception normally indicates some security protocol like a firewall rule that is blocking the requests.

 java.lang.RuntimeException: Client initialization failed. Check if the endpoint is reachable and if your auth token is valid

To validate the SDK can communicate to the Azure Cosmos DB account execute the following command from where the application is hosted. If it fails this points to a firewall rule or other security feature blocking the request. If it succeeds the SDK should be able to communicate to the Azure Cosmos DB account.

telnet myCosmosDbAccountName.documents.azure.com 443

Client-side transient connectivity issues

Service unavailable exceptions can surface when there are transient connectivity problems that are causing timeouts. Typically, the stack trace related to this scenario will contain a ServiceUnavailableException error with diagnostic details. For example:

Exception in thread "main" ServiceUnavailableException{userAgent=azsdk-java-cosmos/4.6.0 Linux/4.15.0-1096-azure JRE/11.0.8, error=null, resourceAddress='null', requestUri='null', statusCode=503, message=Service is currently unavailable, please retry after a while. If this problem persists please contact support.: Message: "" {"diagnostics"}

Follow the request timeout troubleshooting steps to resolve it.


UnknownHostException means that the Java framework can't resolve the DNS entry for the Azure Cosmos DB endpoint in the affected machine. You should verify that the machine can resolve the DNS entry or if you have any custom DNS resolution software (such as VPN or Proxy, or a custom solution), make sure it contains the right configuration for the DNS endpoint that the error is claiming can't be resolved. If the error is constant, you can verify the machine's DNS resolution through a curl command to the endpoint described in the error.

Service outage

Check the Azure status to see if there's an ongoing issue.

Next steps