Connection to MySQL Server Failing on Windows
作者:jit 日期:2008-09-24
When you're running a MySQL server on Windows with many TCP/IP connections to it, and you're experiencing that quite often your clients get a Can't connect to MySQL server error, the reason might be that Windows doesn't allow for enough ephemeral (short-lived) ports to serve those connections.
By default, Windows allows 5000 ephemeral (short-lived) TCP ports to the user. After any port is closed it will remain in a TIME_WAIT status for 120 seconds. This status allows the connection to be reused at a much lower cost than re-initialising a brand new connection. However, the port will not be available again until this time expires.
With a small stack of available TCP ports (5000) and a high number of TCP ports being open and closed over a short period of time along with the TIME_WAIT status you have a good chance for running out of ports. There are two ways to address this problem:
Reduce the number of TCP ports consumed quickly by investigating connection pooling or persistent connections where possible
Start Registry Editor (Regedt32.exe).
Locate the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
On the Edit menu, click Add Value, and then add the following registry value:
Value Name: MaxUserPort
Data Type: REG_DWORD
Value: 65534
This sets the number of ephemeral ports available to any user. The valid range is between 5000 and 65534 (decimal). The default value is 0x1388 (5000 decimal).
On the Edit menu, click Add Value, and then add the following registry value:
Value Name: TcpTimedWaitDelay
Data Type: REG_DWORD
Value: 30
This sets the number of seconds to hold a TCP port connection in TIME_WAIT state before closing. The valid range is between 0 (zero) and 300 (decimal). The default value is 0x78 (120 decimal).
Quit Registry Editor.
Reboot the machine.
By default, Windows allows 5000 ephemeral (short-lived) TCP ports to the user. After any port is closed it will remain in a TIME_WAIT status for 120 seconds. This status allows the connection to be reused at a much lower cost than re-initialising a brand new connection. However, the port will not be available again until this time expires.
With a small stack of available TCP ports (5000) and a high number of TCP ports being open and closed over a short period of time along with the TIME_WAIT status you have a good chance for running out of ports. There are two ways to address this problem:
Reduce the number of TCP ports consumed quickly by investigating connection pooling or persistent connections where possible
Start Registry Editor (Regedt32.exe).
Locate the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
On the Edit menu, click Add Value, and then add the following registry value:
Value Name: MaxUserPort
Data Type: REG_DWORD
Value: 65534
This sets the number of ephemeral ports available to any user. The valid range is between 5000 and 65534 (decimal). The default value is 0x1388 (5000 decimal).
On the Edit menu, click Add Value, and then add the following registry value:
Value Name: TcpTimedWaitDelay
Data Type: REG_DWORD
Value: 30
This sets the number of seconds to hold a TCP port connection in TIME_WAIT state before closing. The valid range is between 0 (zero) and 300 (decimal). The default value is 0x78 (120 decimal).
Quit Registry Editor.
Reboot the machine.
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