ping

ping

The ping command is a no-op used to test whether a server is responding to commands. ping命令是一个no op，用于测试服务器是否响应命令。This command will return immediately even if the server is write-locked:即使服务器被写锁定，此命令也会立即返回：

{ ping: 1 }

The value (e.g. 1 above) does not impact the behavior of the command.该值（例如上面的1）不会影响命令的行为。