I. Introduction

In this tutorial, you learn how to forward the device messages of IoT Core to CFC through Rule Engine and carry out the user-defined data processing through CFC.

II. Application Scenarios Description

The rule engine can filter, modify and forward massive data. However, when you put forward more complex and personalized requirements for device data processing, and it may not meet all requirements using the rule engine only, you can meet relevant processing requirements by combining with CFC. The data processing becomes more flexible and diverse by combining with Rule Engine and CFC. The main application scenarios include:

1. Carry out the data processing in complex scenarios.
2. Store the device log information.
3. Forward the device message to the user-defined service.

III. Example Scenarios Description

To give you an in-depth understanding of the combined use of Rule Engine and CFC, we take a simple example:

• The rule engine forwards the system log generated by the device to CFC.
• CFC decodes the log message received and stores the message content in BOS.

The operation steps are as follows:

1. Create a BOS instance.
2. Create a CFC instance, and configure BOS as the log storage destination.
3. Create an IOT Core instance and a forwarding rule.
4. Verify the device log forwarding and storage function.

IV. Operating Steps

4.1 Create a BOS Instance

For the specific method, please see BOS Creating Bucket.

Log in to the BOS Management console. Click "Bucket List" in the left navigation bar, and find and click the + button in the Bucket list ("New Bucket" button) to create a Bucket in the pop-up box by following the prompts.

Click "Confirm" to complete the creation of this Bucket.

4.2 Creating CFC Instance and Configuring Destination

Select "Create Blank Function".

Select "BOS" as log storage in "unction Configuration. The log storage path is custom.

Select "None" for Trigger.

The rule engine sends the Base64 encoded message content to CFC. For more information, see [Forwarding to CFC Function](https://cloud.baidu.com/doc/IoTCore/s/zkd8kfdc8#Forward to Function Computing#). Therefore, to obtain the data transmitted by the rule engine in CFC, we need to carry out the following two steps:

1. Carry out the Base64 decoding of message in event ['message'].

2. Convert the decoded data into the object according to the description file of Protocol Buffers.

In this tutorial, CFC uses Python3.6 during running, whose function is to decode the device data and print the log.

The Python function program reference code is as follows:

import base64
import time
from google.protobuf import json_format
import json
import MqttLogConstants_pb2 as MqttLog
from TrafficLogEntry_pb2 import TrafficLogEntries
import logging
logging.basicConfig()
logger = logging.getLogger()
logger.setLevel(logging.INFO)

# Decode byte data and convert it into log object
def parse_log_entries(bytes):
    entries = TrafficLogEntries()
    entries.ParseFromString(bytes)
    return entries

# CFC Function Entry
def handler(event, context):
    # base64 decoding
    logBytes=base64.b64decode(event['message'])
    # Decode byte data and convert it into log object
    logEntries = parse_log_entries(logBytes)
    for entry in logEntries.entries:
        if entry.code.startswith('MQT'):
            entryJson = json.loads(json_format.MessageToJson(entry))
            details = entryJson['details']
            newDetails = {}
            for keyNum in details:
                detail = MqttLog.LogDetailKey.Name(int(keyNum))
                newDetails[detail] = details[keyNum]
            entryJson['details'] = newDetails
            # Print the decoding result as a log
            logger.info(entryJson)
    return None

Upload the Python function program processing package.

4.3 Creating IoT Core Instance and Configuring Rule Engine

4.3. 1 Create a IoT Core instance.

Enter the console and click "create IOT core".

After you fill in the information, click "Submit".

After successful creation, the instance is displayed in the instance list.

4.3.2 Add a Template.

Click the "Template" menu in Device Management, and then click "Add Template" to add a template.

Fill in the「template name and click「confirm」.

After confirmation, create a device template named fortest, which can be viewed in the template list.

4.3.3 Add a device.

Click "New Device" to create a device.

Select "Key Authentication" as the authentication mode, and select the template "Forest" created in the previous steps, and then click "Submit".

After successful creation, it displays the key of the device. Click "Download" to save the key record text.

4.3.4 Generating Connection Information

To connect the device, you need to use the MQTT Connection Information Generator to generate the connection authentication information of the device and record the Results (MQTT Connection Information) for standby.

Please save the Connection Authentication Information of Device, which is used in Step 4.4.

4.3.5 Configuring Rule Engine

Log in to the IoT Core console, and find the "Rule List" under the instance, and then click "Create Rule" to create a rule.

After you enter the rule information, click "Confirm" to create a rule.

Click "Edit and Debug" to enter the Edit interface.

Edit the "Input Source" of rule, and then click "Topic Template".

When the device is connected, monitored and disconnected, the log data is recorded in the directory $sys/log/info/#.

Select "SYS_LOG_TOPIC" for the device template, select "$sys/log/info/#" for optional topic.

Click "Rule Destination".

Select "CFC" as the destination, and select the function corresponding to the Python program, and then click 「Save」.

After saving the rule successfully, enter the rule list and start the rule. When the rule is Running, it indicates that the rule takes effect.

4.4 Verifying Device Log Forwarding and Storage Function

On completion of the above steps, the environment has been built, and the device message can be forwarded to CFC through the rule engine. CFC stores the log information generated in BOS.

Fill in the connection authentication information generated in Step 4.3.4 into the MQTT client, and then click "Connect".

Observe the Log in CFC, and you find that the data has been successfully received and transcoded.

The INFO log in the figure above is the log printed in the Python program.

View BOS, and you can see the log file. The device log information is successfully stored, and the verification is completed.