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Use TagHub SDK on Hello World Application 2-python3.md

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Use TagHub SDK on Hello World Application 2

Document Version: V1.0

Change Log
Version Date Content
1.0 2022-02-10 Document created

Purpose

This document guide you how to use TagHub Python SDK on Hello World Application to subscribe Tag data for edge computing.

You shall complete pre-request steps:

1. Add backend.py Python Code

We need to add one python script, running at backend to subscribe Tags and do some edge computing tasks.

1.1 Create backend.py and add Python packages
import time, requests
from thingspro.edge.tag_v1 import tag
  • thingspro.edge.tag_v1 is TagHub Python SDK.
1.2 Add Class: backendProcess and assign initial variables
class backendProcess():
    def __init__(self):
        self.subscriber = tag.Subscriber()
        self.publisher = tag.Publisher()
        self.webAPIURL = 'http://127.0.0.1/api/v1'
        self.headers = {}
        self.headers["Content-Type"] = 'application/json'
  • We will use self.subscriber to subscribe Tag.
  • The backend process will leverage hello-world's Restful API to create virtual tags.
1.3 Create start() method
def start(self):
        # Waiting Web API
        self.waitWebAPI()
        
        # Create virtual tags before subscribe them
        self.createTag('virtual', 'hello-world', 'tag01', 'string')
        self.createTag('virtual', 'hello-world', 'tag02', 'int32')
        self.createTag('virtual', 'hello-world', 'tag03', 'int32')        
        
        # Subscribe virtual tags, and declare call back function        
        self.subscriber.subscribe_callback(self.tagDataCallback)        
        self.subscriber.subscribe('virtual', 'hello-world', ['tag01', 'tag02'])
        
        while True:
            time.sleep(1)

  • We tell Tag Subscriber that we want to subscribe tag01 and tag02, and call we defined method, self.tagDataCallback, when data coming.

  • To prevent failure, we create virtual tags (via hello-world Restful API) again, including 3rd tag (tag03).

1.4 Create tagDataCallback() method
def tagDataCallback(self, data={}):
        timestamp=int(time.time()*1000000)  
        if data["tagName"] == 'tag02':
            F = self.C_to_F(data['dataValue'])
            tag03 = {
                    'prvdName': 'virtual',
                    'srcName': 'hello-world',
                    'tagName': 'tag03',            
                    'dataValue': int(F),
                    'dataType': 'int32',
                    'ts': timestamp        
                }  
            self.publisher.publish(tag03)
            
            if (F >= 100):     
                tag01Value = 'Over Hit'
            else:
                tag01Value = 'Normal'                     
            tag01 = {
                'prvdName': 'virtual',
                'srcName': 'hello-world',
                'tagName': 'tag01',            
                'dataValue': tag01Value,
                'dataType': 'string',
                'ts': timestamp        
            }             
            self.publisher.publish(tag01)
  • We convert tag02 value (temperature) , from °C to °F , and publish temperature °F to tag03.
  • If tag03 value >= 100, publish 'Over Hit' to tag01, else publish 'Normal' to tag01

2. Develop Your Application

2.1 Download Hello World Application 1.3

$ wget https://tpe2.thingspro.io/tpe2/Python3/HelloWorldApp13.tar

2.2 ThingsPro Edge Application 1.2 Structure

Name Type Note
Dockerfile File Updated for launch backend.py and web.py
app Folder Add backend.py
Rename run.py to web.py
docker-compose.yml File Update version to 1.3
metadata.yml File Update version to 1.3
nginx.conf File Same with 1.0
requirements.tx File Same with 1.2

2.3 Build ThingsPro Edge Applicaiton

Follow pre-request step: Build and Run "Hello World" Application, to build hello-world application V1.3

-rwxrwxrwx 1 root root       861 Feb 12 14:07 Dockerfile
drwxrwxrwx 2 root root      4096 Feb 12 15:12 app
-rwxrwxrwx 1 root root        56 Feb 12 16:54 docker-compose.yml
-rw-r--r-- 1 root root 136980480 Feb 13 02:06 hello-world_1.3_armhf.mpkg
-rwxrwxrwx 1 root root       107 Feb 12 16:54 metadata.yml
-rwxrwxrwx 1 root root       281 Feb 12 08:46 nginx.conf
-rwxrwxrwx 1 root root        73 Feb 12 13:07 requirements.txt

3. Deploy Application on Moxa IIoT Gateway

3.1 Deploy hello-world V1.3

Follow pre-request step: Build and Run "Hello World" Application, to deploy hello-world application V1.3

3.2 Testing
3.3.1 Update virtual tags value by PUT /api/v1/hello-world/tag
curl -X PUT https://127.0.0.1:8443/api/v1/hello-world/tag -H "mx-api-token:$(cat /var/thingspro/data/mx-api-token)" -H "Content-Type:application/json" -k -d '{"prvdName":"virtual","srcName":"hello-world","tagName":"tag02", "dataValue":20, "dataType":"int32"}'

curl -X PUT https://127.0.0.1:8443/api/v1/hello-world/tag -H "mx-api-token:$(cat /var/thingspro/data/mx-api-token)" -H "Content-Type:application/json" -k -d '{"prvdName":"virtual","srcName":"hello-world","tagName":"tag02", "dataValue":4040, "dataType":"int32"}'
3.2.2 Monitor these two virtual tags on ThingsPro Edge Web Admin

Add Tag03 into monitoring.

ThingsPro Edge Web Admin / Tag Management offers a easy way to monitor Tag value changed.

This feature is available on ThingsPro Edge V2.2.1+.

3.3 Done and Next Action