Overview

The DragonConnect example utilizes the following Lambda functions written in JavaScript

• DragonConnect-things
• DragonConnect-led
• DragonConnect-audioEvents

Lambda Function Management

The following tasks have been defined to create, update, and delete the DragonConnect Lambda functions.

Create

The Lambda functions rely upon the general DragonConnect configuration and Grunt, a JavaScript Task Runner. The NODE_PATH environment variable should be set to include the lib directory. This allows multiple modules to work provided that the script is run from the module root. The following steps will deploy the Lambda functions

$ cd lambda
$ export NODE_PATH=lib
$ npm install ../config
$ npm install -g grunt-cli
$ npm install
$ grunt create

When these steps have been completed, the Lambda functions will be available for use. You can check their availability either through the AWS console or by using the following command (remember to use a backtick(`) around the DragonConnect string)

$ aws lambda list-functions \
--query 'Functions[?FunctionName.contains(@, `DragonConnect`)]'

The create task, in addition to packaging and deploying the Lambda function, will also add the appropriate permissions. The permissions needed by a Lambda function are mentioned in the Detail section.

Update

If you decide to experiment and alter the functionality of a Lambda function, a grunt task has been defined to perform an update. The following command will perform an update of all the Lambda functions

$ grunt update

Delete

In order to delete the Lambda functions, use the following command

$ grunt delete

Targets

The above commands will perform the task for all Lambda functions. If you would like to perform the task for a particular Lambda function use the following command

$ grunt ${task}:${target}

where task may be create, update, or delete and target would have a value of

Detail

The management of the Lambda functions require each function to be packaged and the AWS Lambda service to be configured. In addition, the functionality of each Lambda function is discussed.

Package

Each Lambda function is packaged using Browserify and Uglify. This reduces the size of the Lambda function and improves startup performance.

Amazon includes the JavaScript aws-sdk within the Lambda environment and therefore it is excluded when performing the packaging of the function.

Configuration

The DragonConnect Lambda functions use the same configuration of utilizing 1024 MB of memory and a timeout of 5 seconds. In addition, each Lambda function is configured to use the DragonConnect-Lambda IAM role.

Function Descriptions

Each Lambda function represents the operations that may be performed on a resource (API Gateway).

• DragonConnect-things

  The DragonConnect-things function will retrieve information about all things or about a specific thing. The function only returns a thing if it has an associated principal (certificate). Thus, you may notice a difference between the output of the command

  $ aws iot list-things
  

  and the things returned by this function.

  Essentially, this Lambda function provides the capabilities of the API to perform

  • GET /things
  • GET /things/{thingId}

  As you will see in the step, Manage Things, a utility will create a thing, a certificate (principal), and will associate the thing to the principal as well as the DragonConnect IoT policy.

• DragonConnect-led

  The DragonConnect-led function will retrieve the current state of the device shadow as well as request an update of the state. The state of the device shadow is simply defined as

  {
    "active": false
  }
  

  where a value of false represents the LED being off and true represents the LED being on.

  This Lambda function enables the following API operations

  • GET /things/{thingId}/led
  • POST /things/{thingId}/led

• DragonConnect-audioEvents

  The DragonConnect-audioEvents function will create an audio event when the volume up or volume down button is pressed. The volume up or down event includes a timestamp in seconds from the epoch (UTC)

  {
    "volume": "increase",
    "timestamp": 1451685789
  }
  

  Volume may have a value of either increase or decrease. A value of increase represents the volume up button being pressed and decrease represents the volume down button being pressed.

  The DragonConnect-audioEvents Lambda function enables audio events to be created when messages are published to the things/+/audio/events MQTT topic.

  The IoT service does not currently support a role-based permission model. Instead a resource-based permission must be configured that allows the DragonConnect-audioEvents Lambda function to be invoked. The create task configures this permission. For more information, see Create a Rule to Invoke a Lambda Function of Configure and Test Rules in the IoT Developer Guide.

  This function also enables the following API operation

  • GET /things/{thingId}/audio/events?limit=10