Schedule and broadcast jobs (Python)

Use Azure IoT Hub to schedule and track jobs that update millions of devices. Use jobs to:

• Update desired properties
• Update tags
• Invoke direct methods

Conceptually, a job wraps one of these actions and tracks the progress of execution against a set of devices, which is defined by a device twin query. For example, a back-end app can use a job to invoke a reboot method on 10,000 devices, specified by a device twin query and scheduled at a future time. That application can then track progress as each of those devices receives and executes the reboot method.

Learn more about each of these capabilities in these articles:

• Device twin and properties: Get started with device twins and Understand and use device twins in IoT Hub

• Direct methods: IoT Hub developer guide - direct methods and Quickstart: direct methods

This article shows you how to create two Python apps:

• A Python simulated device app, simDevice.py, that implements a direct method called lockDoor, which can be called by the back-end app.

• A Python console app, scheduleJobService.py, that creates two jobs. One job calls the lockDoor direct method and another job sends desired property updates to multiple devices.

Prerequisites

• An active Azure account. (If you don't have an account, you can create a Trial in just a couple of minutes.)

• An IoT Hub. Create one with the CLI or the Azure portal.

• A registered device. Register one in the Azure portal.

• Python version 3.7 or later is recommended. Make sure to use the 32-bit or 64-bit installation as required by your setup. When prompted during the installation, make sure to add Python to your platform-specific environment variable.

Create a simulated device app

In this section, you create a Python console app that responds to a direct method called by the cloud, which triggers a simulated lockDoor method.

1. At your command prompt, run the following command to install the azure-iot-device package:

   pip install azure-iot-device
   

2. Using a text editor, create a new simDevice.py file in your working directory.

3. Add the following import statements and variables at the start of the simDevice.py file. Replace deviceConnectionString with the connection string of the device you created above:

   import time
   from azure.iot.device import IoTHubDeviceClient, MethodResponse
   
   CONNECTION_STRING = "{deviceConnectionString}"
   

4. Define the following function, which will instantiate a client and configure it to respond to the lockDoor method, as well as receive device twin updates:

   def create_client():
       # Instantiate the client
       client = IoTHubDeviceClient.create_from_connection_string(CONNECTION_STRING)
   
       # Define behavior for responding to the lockDoor direct method
       def method_request_handler(method_request):
           if method_request.name == "lockDoor":
               print("Locking Door!")
   
               resp_status = 200
               resp_payload = {"Response": "lockDoor called successfully"}
               method_response = MethodResponse.create_from_method_request(
                   method_request=method_request,
                   status=resp_status,
                   payload=resp_payload
               )
               client.send_method_response(method_response)
   
       # Define behavior for receiving a twin patch
       def twin_patch_handler(twin_patch):
           print("")
           print("Twin desired properties patch received:")
           print(twin_patch)
   
       # Set the handlers on the client
       try:
           print("Beginning to listen for 'lockDoor' direct method invocations...")
           client.on_method_request_received = method_request_handler
           print("Beginning to listen for updates to the Twin desired properties...")
           client.on_twin_desired_properties_patch_received = twin_patch_handler
       except:
           # If something goes wrong while setting the handlers, clean up the client
           client.shutdown()
           raise
   

5. Add the following code to run the sample:

   def main():
       print ("Starting the IoT Hub Python jobs sample...")
       client = create_client()
   
       print ("IoTHubDeviceClient waiting for commands, press Ctrl-C to exit")
       try:
           while True:
               time.sleep(100)
       except KeyboardInterrupt:
           print("IoTHubDeviceClient sample stopped!")
       finally:
           # Graceful exit
           print("Shutting down IoT Hub Client")
           client.shutdown()
   
   
   if __name__ == '__main__':
       main()
   

6. Save and close the simDevice.py file.

Get the IoT Hub connection string

In this article, you create a backend service that invokes a direct method on a device and updates the device twin. The service needs the service connect permission to call a direct method on a device. The service also needs the registry read and registry write permissions to read and write the identity registry. There is no default shared access policy that contains only these permissions, so you need to create one.

To create a shared access policy that grants service connect, registry read, and registry write permissions and to get a connection string for this policy, follow these steps:

1. Open your IoT hub in the Azure portal. The easiest way to get to your IoT hub is to select Resource groups, select the resource group where your IoT hub is located, and then select your IoT hub from the list of resources.

2. On the left-side pane of your IoT hub, select Shared access policies.

3. From the top menu above the list of policies, select Add shared access policy.

4. On the Add shared access policy pane, enter a descriptive name for your policy; for example: serviceAndRegistryReadWrite. Under Permissions, select Registry Write and Service Connect (Registry Read is automatically selected when you select Registry Write) then select Add.

   

5. Back on the Shared access policies page, select your new policy from the list of policies.

6. In the new pane that appears, select the copy icon for the Primary connection string and save the value.

   

For more information about IoT Hub shared access policies and permissions, see Access control and permissions.

Schedule jobs for calling a direct method and updating a device twin's properties

In this section, you create a Python console app that initiates a remote lockDoor on a device using a direct method and also updates the device twin's desired properties.

1. At your command prompt, run the following command to install the azure-iot-hub package:

   pip install azure-iot-hub
   

2. Using a text editor, create a new scheduleJobService.py file in your working directory.

3. Add the following import statements and variables at the start of the scheduleJobService.py file. Replace the {IoTHubConnectionString} placeholder with the IoT hub connection string you copied previously in Get the IoT hub connection string. Replace the {deviceId} placeholder with the device ID (the name) from your registered device:

   import os
   import sys
   import datetime
   import time
   import threading
   import uuid
   import msrest
   
   from azure.iot.hub import IoTHubJobManager, IoTHubRegistryManager
   from azure.iot.hub.models import JobProperties, JobRequest, Twin, TwinProperties, CloudToDeviceMethod
   
   CONNECTION_STRING = "{IoTHubConnectionString}"
   DEVICE_ID = "{deviceId}"
   
   METHOD_NAME = "lockDoor"
   METHOD_PAYLOAD = "{\"lockTime\":\"10m\"}"
   UPDATE_PATCH = {"building":43,"floor":3}
   TIMEOUT = 60
   WAIT_COUNT = 5
   
   # Create IoTHubJobManager
   iothub_job_manager = IoTHubJobManager.from_connection_string(CONNECTION_STRING)
   
   

4. Add the following methods to run the jobs that call the direct method and device twin:

   def device_method_job(job_id, device_id, execution_time):
       print ( "" )
       print ( "Scheduling job: " + str(job_id) )
   
       job_request = JobRequest()
       job_request.job_id = job_id
       job_request.type = "scheduleDeviceMethod"
       job_request.start_time = datetime.datetime.utcnow().isoformat()
       job_request.cloud_to_device_method = CloudToDeviceMethod(method_name=METHOD_NAME, payload=METHOD_PAYLOAD)
       job_request.max_execution_time_in_seconds = execution_time
       job_request.query_condition = "DeviceId in ['{}']".format(device_id)
   
       new_job_response = iothub_job_manager.create_scheduled_job(job_id, job_request)
   
   def device_twin_job(job_id, device_id, execution_time):
       print ( "" )
       print ( "Scheduling job " + str(job_id) )
   
       job_request = JobRequest()
       job_request.job_id = job_id
       job_request.type = "scheduleUpdateTwin"
       job_request.start_time = datetime.datetime.utcnow().isoformat()
       job_request.update_twin = Twin(etag="*", properties=TwinProperties(desired=UPDATE_PATCH))
       job_request.max_execution_time_in_seconds = execution_time
       job_request.query_condition = "DeviceId in ['{}']".format(device_id)
   
       new_job_response = iothub_job_manager.create_scheduled_job(job_id, job_request)
   
   

5. Add the following code to schedule the jobs and update job status. Also include the main routine:

   def iothub_jobs_sample_run():
       try:
           method_job_id = uuid.uuid4()
           device_method_job(method_job_id, DEVICE_ID, TIMEOUT)
   
           print ( "" )
           print ( "Direct method called with Job Id: " + str(method_job_id) )
   
           twin_job_id = uuid.uuid4()
           device_twin_job(twin_job_id, DEVICE_ID, TIMEOUT)
   
           print ( "" )
           print ( "Device twin called with Job Id: " + str(twin_job_id) )
   
           while True:
               print ( "" )
   
               method_job_status = iothub_job_manager.get_scheduled_job(method_job_id)
               print ( "...job " + str(method_job_id) + " " + method_job_status.status )
   
               twin_job_status = iothub_job_manager.get_scheduled_job(twin_job_id)
               print ( "...job " + str(twin_job_id) + " " + twin_job_status.status )
   
               print ( "Job status posted, press Ctrl-C to exit" )
               time.sleep(WAIT_COUNT)
   
       except msrest.exceptions.HttpOperationError as ex:
           print ( "" )
           print ( "Http error {}".format(ex.response.text) )
           return
       except Exception as ex:
           print ( "" )
           print ( "Unexpected error {}".format(ex) )
           return
       except KeyboardInterrupt:
           print ( "" )
           print ( "IoTHubService sample stopped" )
   
   if __name__ == '__main__':
       print ( "Starting the IoT Hub jobs Python sample..." )
       print ( "    Connection string = {0}".format(CONNECTION_STRING) )
       print ( "    Device ID         = {0}".format(DEVICE_ID) )
   
       iothub_jobs_sample_run()
   

6. Save and close the scheduleJobService.py file.

Run the applications

You are now ready to run the applications.

1. At the command prompt in your working directory, run the following command to begin listening for the reboot direct method:

   python simDevice.py
   

2. At another command prompt in your working directory, run the following command to trigger the jobs to lock the door and update the twin:

   python scheduleJobService.py
   

3. You see the device responses to the direct method and device twins update in the console.

   

   

Next steps

In this article, you scheduled jobs to run a direct method and update the device twin's properties.

To continue getting started with IoT Hub and device management patterns such as remote over the air firmware update, see How to do a firmware update.