# When will my quantum task run?
<a name="braket-task-when"></a>

When you submit a circuit, Amazon Braket sends it to the device you specify. Quantum Processing Unit (QPU) and on-demand simulator quantum tasks are queued and processed in the order they are received. The time required to process your quantum task after you submit it varies depending on the number and complexity of tasks submitted by other Amazon Braket customers and the availability of the QPU selected.

**Topics**
+ [QPU availability windows and status](#braket-qpu-availability)
+ [Queue visibility](#braket-queue-visibility)
+ [Set up email or SMS notifications](status-change-notifications-in-email-or-sms.md)

## QPU availability windows and status
<a name="braket-qpu-availability"></a>

QPU availability varies from device to device.

In the **Devices** page of the Amazon Braket console, you can see the current and upcoming availability windows and device status. Additionally, each device page shows individual queue depths for quantum tasks and hybrid jobs. 

A device is considered *offline* if is not available to customers, regardless of availability window. For example, it could be offline due to scheduled maintenance, upgrades, or operational issues.

## Queue visibility
<a name="braket-queue-visibility"></a>

Before submitting a quantum task or hybrid job, you can view how many quantum tasks or hybrid jobs are in front of you by checking device queue depth.

**Queue depth**

Queue depth refers to the number of quantum tasks and hybrid jobs queued for a particular device. A device's quantum task and hybrid job queue count are accessible through the Braket Software Development Kit (SDK) or Amazon Braket Management Console. 

1. *Task queue depth* refers to the total number of quantum tasks currently waiting to run in normal priority.

1. *Priority task queue depth* refers to the total number of submitted quantum tasks waiting to run through Amazon Braket Hybrid Jobs. These tasks run before standalone tasks.

1. *Hybrid jobs queue depth* refers to the total number of hybrid jobs currently queued on a device. Quantum tasks submitted as part of a hybrid job have priority, and are aggregated in the Priority Task Queue.

Customers wishing to view queue depth through the Braket SDK can modify the following code snippet to get the queue position of their quantum task or hybrid job: 

```
device = AwsDevice("arn:aws:braket:us-east-1::device/qpu/ionq/Forte-Enterprise-1")

# returns the number of quantum tasks queued on the device 
print(device.queue_depth().quantum_tasks)
{<QueueType.NORMAL: 'Normal'>: '0', <QueueType.PRIORITY: 'Priority'>: '0'}


# returns the number of hybrid jobs queued on the device
print(device.queue_depth().jobs)
'3'
```

Submitting a quantum task or hybrid job to a QPU may result in your workload being in a `QUEUED` state. Amazon Braket provides customers visibility into their quantum task and hybrid job queue position. 

**Queue position**

Queue position refers to the current position of your quantum task or hybrid job within a respective device queue. It can be obtained for quantum tasks or hybrid jobs through the Braket Software Development Kit (SDK) or Amazon Braket Management Console. 

Customers wishing to view queue position through the Braket SDK can modify the following code snippet to get the queue position of their quantum task or hybrid job: 

```
# choose the device to run your circuit 
device = AwsDevice("arn:aws:braket:eu-north-1::device/qpu/iqm/Garnet")
 
#execute the circuit 
task = device.run(bell, s3_folder, shots=100)

# retrieve the queue position information
print(task.queue_position().queue_position)
    
# Returns the number of Quantum Tasks queued ahead of you
'2'
        

from braket.aws import AwsQuantumJob

job = AwsQuantumJob.create(
    "arn:aws:braket:eu-north-1::device/qpu/iqm/Garnet",
    source_module="algorithm_script.py",
    entry_point="algorithm_script:start_here",
    wait_until_complete=False
)

# retrieve the queue position information
print(job.queue_position().queue_position)
'3' # returns the number of hybrid jobs queued ahead of you
```

# Set up email or SMS notifications
<a name="status-change-notifications-in-email-or-sms"></a>

Amazon Braket sends events to Amazon EventBridge when the availability of a QPU changes or when the state of your quantum task changes. Follow these steps to receive device and quantum task status change notifications by email or SMS message:

1. Create an Amazon SNS topic and a subscription to email or SMS. Availability of email or SMS depends on your Region. For more information, see [Getting started with Amazon SNS](https://docs.aws.amazon.com/sns/latest/dg/sns-getting-started.html) and [Sending SMS messages](https://docs.aws.amazon.com/sns/latest/dg/sns-mobile-phone-number-as-subscriber.html).

1. Create a rule in EventBridge that triggers the notifications to your SNS topic. For more information, see [Monitoring Amazon Braket with Amazon EventBridge](braket-monitor-eventbridge.md).

## (Optional) Set up SNS notifications
<a name="braket-sns-notifications"></a>

You can set up notifications through the Amazon Simple Notification Service (SNS) so that you receive an alert when your Amazon Braket quantum task is complete. Active notifications are useful if you expect a long wait time; for example, when you submit a large quantum task or when you submit a quantum task outside of a device's availability window. If you do not want to wait for the quantum task to complete, you can set up an SNS notification.

An Amazon Braket notebook walks you through the setup steps. For more information, see [the Amazon Braket examples on GitHub](https://github.com/aws/amazon-braket-examples) and, specifically, [the example notebook for setting up notifications](https://github.com/aws/amazon-braket-examples/tree/main/examples/braket_features).