(mongodb >=1.11.0)
MongoDB\Driver\Monitoring\CommandStartedEvent::getServiceId — Returns the load balancer service ID for the command
When the driver is connected to a MongoDB cluster through a load balancer,
the service ID corresponds to the serviceId field in the
hello command response.
此函數沒(méi)有參數。
Returns the load balancer service ID, or null if the driver is not
connected to a load balancer.