Connecting to an Azure SQL database
This article discusses issues when using the Microsoft JDBC Driver for SQL Server to connect to a Azure SQL Database. For more information about connecting to a Azure SQL Database, see:
When connecting to a Azure SQL Database, you should connect to the master database to call SQLServerDatabaseMetaData.getCatalogs.
Azure SQL Database doesn't support returning the entire set of catalogs from a user database. SQLServerDatabaseMetaData.getCatalogs use the sys.databases view to get the catalogs. Please refer to the discussion of permissions in sys.databases (Transact-SQL) to understand SQLServerDatabaseMetaData.getCatalogs behavior on a Azure SQL Database.
When connecting to a Azure SQL Database, idle connections may be terminated by a network component (such as a firewall) after a period of inactivity. There are two types of idle connections, in this context:
Idle at the TCP layer, where connections can be dropped by any number of network devices.
Idle by the SQL Azure Gateway, where TCP keepalive messages might be occurring (making the connection not idle from a TCP perspective), but not had an active query in 30 minutes. In this scenario, the Gateway will determine that the TDS connection is idle at 30 minutes and terminate the connection.
To avoid dropping idle connections by a network component, the following registry settings (or their non-Windows equivalents) should be set on the operating system where the driver is loaded:
|Registry Setting||Recommended Value|
|HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Tcpip \ Parameters \ KeepAliveTime||30000|
|HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Tcpip \ Parameters \ KeepAliveInterval||1000|
|HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Tcpip \ Parameters \ TcpMaxDataRetransmissions||10|
Restart the computer for the registry settings to take effect.
To accomplish this when running in Azure create a startup task to add the registry keys. For example, add the following Startup task to the service definition file:
<Startup> <Task commandLine="AddKeepAlive.cmd" executionContext="elevated" taskType="simple"> </Task> </Startup>
Then add a AddKeepAlive.cmd file to your project. Set the "Copy to Output Directory" setting to Copy always. The following is a sample AddKeepAlive.cmd file:
if exist keepalive.txt goto done time /t > keepalive.txt REM Workaround for JDBC keep alive on SQL Azure REG ADD HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters /v KeepAliveTime /t REG_DWORD /d 30000 >> keepalive.txt REG ADD HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters /v KeepAliveInterval /t REG_DWORD /d 1000 >> keepalive.txt REG ADD HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters /v TcpMaxDataRetransmissions /t REG_DWORD /d 10 >> keepalive.txt shutdown /r /t 1 :done
Appending the server name to the userId in the connection string
Prior to the 4.0 version of the Microsoft JDBC Driver for SQL Server, when connecting to an Azure SQL Database, you were required to append the server name to the UserId in the connection string. For example, user@servername. Beginning in version 4.0 of the Microsoft JDBC Driver for SQL Server, it's no longer necessary to append @servername to the UserId in the connection string.
Using encryption requires setting hostNameInCertificate
Prior to the 7.2 version of the Microsoft JDBC Driver for SQL Server, when connecting to an Azure SQL Database, you should specify hostNameInCertificate if you specify encrypt=true (If the server name in the connection string is shortName.domainName, set the hostNameInCertificate property to *.domainName.). This property is optional as of version 7.2 of the driver.