If you specify the Initial Capacity when creating a scaling group, after you create the launch configuration and scaling group, the scaling group creates new CVM instances equal to the starting number of instances. At the same time, the scaling group ensures that there are running instances greater than the Min Capacity and less than the Max Capacity.
Notes:
- Min Capacity: The minimum number of instances allowed in a scaling group. When the number of CVMs in a scaling group is less than the minimum number of instances, the AS adds instances so that the current number of instances in the scaling group matches the minimum number of instances.
- Initial Capacity: The number of CVM when the scaling group is created.
- Max Capacity: The maximum number of instances allowed in a scaling group. When the number of CVMs in a scaling group is greater than the maximum number of instances, the AS removes instances so that the current number of instances in the scaling group matches the maximum number of instances.
To keep the instances in the scaling group running normally, AS performs regular examinations on the running state of the instances in the scaling group. If it finds an instance is unhealthy, it terminates the instance and launches a new CVM instance.
- Instance Health Examination:
The scaling group periodically checks the instance running state to determine whether each instance is healthy. The judgment standard is whether the machine is unreachable by ping for 1 consecutive minute. If an instance is unreachable by ping for more than 1 minute, the AS marks the instance as unhealthy. - Replacing Unhealthy Instances:
After an unhealthy instance is marked as unhealthy, the scaling group immediately launches a new instance to replace it (except for machines with a removal protection set).