# Track Amazon ECS Availability Zone rebalancing
<a name="track-service-rebalancing"></a>

You can verify if Availability Zone rebalancing is enabled for a service in the console or by calling `describe-services`. The following example can be used to see the status with the CLI.

The response will be either `ENABLED` or `DISABLED`.

```
aws ecs describe-services \
    --services service-name \
    --cluster cluster-name \
    --query services[0].availabilityZoneRebalancing
```

## Service events
<a name="service-info-events"></a>

Amazon ECS sends service action events to help you understand the Availability Zone rebalancing lifecycle. 


| Event | Scenario | Type | Learn more | 
| --- | --- | --- | --- | 
| SERVICE\$1REBALANCING\$1STARTED | Amazon ECS starts an Availability Zone rebalancing operation | INFO | [service (*service-name*) is not AZ balanced with *number-tasks* tasks in *Availability Zone 1*, *number-tasks* in *Availability Zone 2*, and *number-tasks* in *Availability Zone 3*. AZ Rebalancing in progress.](service-rebalancing-event-messages-list.md#service-rebalancing-started) | 
| SERVICE\$1REBALANCING\$1COMPLETED | The Availability Zone rebalancing operation completes |  INFO | [service (*service-name*) is AZ balanced with *number-tasks* tasks in *Availability Zone 1*, *number-tasks* tasks in *Availability Zone 2*, and *number-tasks* tasks in *Availability Zone 3*.](service-rebalancing-event-messages-list.md#service-rebalancing-completed) | 
| TASKS\$1STARTED | Amazon ECS successfully starts tasks as part of the Availability Zone rebalancing operation | INFO | [*service-name* has started *number-tasks* tasks in *Availability Zone* to AZ Rebalance: *task-ids*.](service-rebalancing-event-messages-list.md#service-rebalancing-tasks-started) | 
| TASKS\$1STOPPED | Amazon ECS successfully stops tasks as part of the Availability Zone rebalancing operation | INFO | [*service-name* has stopped *number-tasks* running tasks in *Availability Zone* due to AZ rebalancing: *task-id*.](service-rebalancing-event-messages-list.md#service-rebalancing-tasks-stopped) | 
| SERVICE\$1TASK\$1PLACEMENT\$1FAILURE | Amazon ECS failed to start a task as part of the Availability Zone rebalancing operation | ERROR | For EC2, see [service (*service-name*) is unable to place a task in *Availability Zone* because no container instance met all of its requirements.](service-rebalancing-event-messages-list.md#service-rebalancing-placement-failure-instance) For the Fargate, see [service (*service-name*) is unable to place a task in *Availability Zone*.](service-rebalancing-event-messages-list.md#service-rebalancing-placement-failure) | 
| TASKSET\$1SCALE\$1IN\$1FAILURE\$1BY\$1TASK\$1PROTECTION | The Availability Zone rebalancing operation is blocked because task protection is in use. | INFO | [service (*service-name*) was unable to AZ Rebalance because *task-set-name* was unable to scale in due to *reason*.](service-rebalancing-event-messages-list.md#service-rebalancing-task-protection-failure) | 
| SERVICE\$1REBALANCING\$1STOPPED | The Availability Zone rebalancing operation stopped. Amazon ECS sends additional events which provide more information. | INFO | [service (*service-name*) stopped AZ Rebalancing.](service-rebalancing-event-messages-list.md#service-rebalancing-operation-stopped) | 

## Task state change events
<a name="task-state-change-events"></a>

Amazon ECS sends a task state change event (`START`) for each task that it starts as part of the rebalancing process.

Amazon ECS sends a task state change event (`STOPPED`) event for each task that it stops as part of the rebalancing process. The reason is set to `Availability-zone rebalancing initiated by (deployment ecs-svc/deployment-id)`.

For more information about the events, see [Amazon ECS task state change events](ecs_task_events.md).