Local process control

Step 1: Create a process control function

1. Download the local process control function querySqliteDB-code.zip.
2. Log on to the Function Compute console.
   If you have not activated this service, read the terms and select I have read and agree to the terms. Then, click Activate Now.
3. (Optional) In the navigation pane on the left, click Services & Functions. On the Services & Functions page, in the Service List section, click Create Service to create a service.
   The Service Name parameter is required. Set this parameter to EdgeFC. You can configure the other parameters as needed or use their default settings.

   Note

   • If this is your first time creating a service in Function Compute, follow the configuration wizard.
   • If you have already created the EdgeFC service for other scenarios or miniprogram examples, you do not need to create it again.
4. After the service is created, on the Services & Functions page, find the EdgeFC service and click Create Function.
5. On the Create Function page, click Configure and Deploy in the Event Function section.
6. Set the basic management configuration parameters for the process control function.

   Parameter	Description
   Function Type	Keep the default option.
   Service	Select the EdgeFC service that you created.
   Function Name	Set it to querySqliteDB.
   Runtime	Set the function runtime and select a method to upload the code. In this example, select Python 3. To the right of Upload Code, select Upload a ZIP file. Click Upload Code and upload the querySqliteDB-code.zip package that you downloaded in Step 1.
   Handler	Use the default value: index.handler.

   You can configure the other parameters as needed or use their default settings. For more information, see Function Compute.

   After you confirm the function information, click Create.

7. After the function is created, the system automatically navigates to the function details page. On the Code tab, in the Code Execution Management section, select the Edit Online radio button to view the source code.
   

   Note The sample code for querySqliteDB consists of three steps.

   1. Parses the productKey and deviceName from the received device data (the event parameter) to form the database table name.

      edict = json.loads(event)
      topic = edict['topic']
      tlist = topic.split('/')
      if tlist[1] == 'sys':
        productKey = tlist[2]
        deviceName = tlist[3]
        tableName = productKey+'_'+deviceName
        print("-- Table Name : "+tableName)

   2. Retrieves all data reported by the LightSensor sensor within the last 5 minutes and calculates the average value.

      cursor.execute("SELECT avg(VALUE) FROM {} WHERE KEY = ? AND TIMESTAMP >= datetime('now','-5 minutes','localtime')".format(tableName), [key])
      avg_value = cursor.fetchone()[0]

   3. If the average value of the data reported by the LightSensor sensor is greater than a specific threshold (in this case, a light intensity of 240), it turns off the Light device.

      if avg_value > 240:
        print("-- Turn off the Light.")
        set_params = {"productKey": "a1ZJTVs****","deviceName": "LightDev","payload": {"LightSwitch":0}}
        res = lesdk.setThingProperties(set_params)

Step 2: Assign the function to an edge instance

1. Log on to the IoT Edge console.
2. In the navigation pane on the left, click Application Management.
3. Create an edge application of the Function Compute type using the function that you created in Step 1. For more information, see Function Compute application.

   The application information parameters are described as follows:

   Parameter	Description
   Application Name	Set a name for your application, for example, querySqliteDB.
   Application Type	Select Function Compute.
   Region	Select the region where your service was created.
   Service	Select the EdgeFC service.
   Function	Select the querySqliteDB function.
   Authorization	Select AliyunIOTAccessingFCRole.
   Application Version	Set the version for the application. The version number must be unique for this application. You cannot set two identical version numbers for the same application.

   In the Function Configuration section, set Enable Default Configurations to Yes. The other parameters can be left at their default settings.

4. In the navigation pane on the left, click Edge Instances.
5. Find the edge instance that you created in the "Prerequisites" section and click View.
6. On the Instance Details page, go to the Edge Applications tab and click Assign Application.
7. In the Assign Application panel, find the created process control function querySqliteDB, click Assign in the Actions column, and then click Close .

Step 3: Configure message routing

This topic explains how to add messages and describes each parameter. For more information, see Set message routing.

1. On the Instance Details page, click the Message Routing tab.
2. Click Assign Route to add a message route from the LightSensor device to Function Compute.
   Set the following parameters as prompted on the page, and then click OK .

   Parameter	Description
   Route Name	Set a name for the message route.
   Message Source	In this example, select Device, and then select Light Sensor > LightSensor.
   Topic Filter	In this example, select All.
   Message Target	In this example, select Edge Application and the EdgeFC/querySqliteDB function.

Step 4: Deploy the edge instance

1. On the Instance Details page, click Deploy in the upper-right corner. In the dialog box that appears, click OK to deploy resources, such as sub-devices and functions, to the edge.
2. Log on to your gateway using Secure Shell (SSH) and run the tail -f /linkedge/run/logger/fc-base/querySqliteDB/log.INFO command.
   The local process control function of edge Function Compute runs as a background service. You can view the logs of this function to monitor its operation.

   You have now completed the process of using edge Function Compute to implement local process control.