最近在做一個Azure雲專案，前臺是Java程式碼，Java程式碼裡使用JDBC驅動訪問SQL Azure。

用了JDBC 連線串後，發現2分鐘左右連線就超時timeout，原來在SQL Server上是能正常工作的。

jdbc:sqlserver://XXXX.database.windows.net:1433;database=miap;[email protected];password=myPassword;encrypt=true;hostNameInCertificate=*.database.windows.net

理論上SQL Azure會在30分鐘後把idle connection

Maximumallowable durations are subject to change depending on the resource usage.A logged-in session that hasbeen idle for 30 minutes will be terminated automatically. We stronglyrecommend that you use the connection pooling and always close the connectionwhen you are finished using it so that the unused connection will be returnedto the pool.

目前ado.net 連線是符合上述文件的。但是，JDBC連線還需要一些額外設定，如下面的論壇網址中所描述：

I rewrote the Java program in C Sharp, and predictably that worksfine and DOES NOT exhibit the connection drop problems.

I used Wireshark to compare the Java and .NET implementations at theTCP level and the problem becomes clear:

TCP Keep-Alivemessages are sent to SQL Azure every 30 seconds from the .NET code, but thereare no such messages from JDBC, hence the JDBC connection times out at betweenabout 61 to 63 seconds.

You must then restart the computer for the registry settings to take effect.

To accomplish this when running in Windows 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 TcpMaxDataRetransmission /t REG_DWORD /d 10 >> keepalive.txt
shutdown /r /t 1
:done