README.md

Amazon Lambda

Official Documentation

A simple Lambda is used to transfer data between the IoT system and DynamoDB. This is executed when data appears on MQTT.

See the IoT documentation on how to add an Action to an IoT MQTT endpoint to trigger a Lambda.

Lambda Script

// console.log('Loading function');
var AWS = require('aws-sdk');
var dynamodb = new AWS.DynamoDB();
var docClient = new AWS.DynamoDB.DocumentClient();

exports.handler = (event, context, callback) => {
    
//    console.log("event.msgid="+event.msgid);
//    console.log("event.temp="+event.temp);
//    console.log("event.pressure="+event.pressure);
    var tableName = "aws-iot-java";    
    
    var params = {
        TableName: 'aws-iot-java',
        Item: {
            'msg-id': event.msgid,
            'caldate': event.caldate,
            'calminute': event.calminute,
            'pitemp0': event.pitemp0,
            'pihum0': event.pihum0,
            'pipress0': event.pipress0
            
        }
    }
    
    docClient.put(params,  function(err, data) {
        if (err) {
            console.log('Error putting item into dynamodb failed: '+err);
        }
        else {
            console.log('great success: '+JSON.stringify(data, null, '  '));
        }
    });
};

Function

The script is called with the data presented to MQTT. The event holds the data sent, context is present so the function can interact with AWS Lambda environment to get useful runtime information such as time remaining, and callback can be used to explicitly return information back to the caller.

Writing to DynamoDB is achieved through a call to put using the DocumentClient. Success / failure handling is achieved by a callback function supplied in the put call along side the data.