DynamoDB Event Streams

An Intro to DynamoDB Event Streams

You are looking for a database endpoint that has a very quick response time is schema less and can alert you when data changes. For this tip we will implement this solution using AWS – DynamoDB, DynamoDB is AWS’s schema less database solution. In This tip we take a look at how to implement a DynamoDB table, build a lambda function that will alert our slack channel when data in that table is changed.

Project Workflow

For this project we will be working in 3 main workspaces, Slack, your personal work station and AWS. To complete this project, you will need:

• A free tier Slack account • An AWS Free tier account • Python installed on your work station

Solution – Step 1 Create the Slack Channel This same logic can be implemented with MS Teams or other webhook supported technologies, but in this example, I will be implementing with slack. If you do not have a slack account you can sign up for free here: https://slack.com/get-started#/ . Once you have an account, we need to create a channel, click the + button next to channels » Create a channel.

Name your channel and click create

Solution – Step 2 Enable app Webhook Now that we have the channel created, we need to add an “app” to the channel. Click the Add an App link in the newly created channel header:

In the search bar type webhook, the one we want is Incoming WebHook for our channel, click install:

Click Add to Slack

Select the channel you want the notifications to go to, click “Add Incoming WebHooks Integration”:

Take a note of the URL provided on the following screen, this URL is a unique endpoint that points to your particular slack channel.

Solution – Step 3 Create the Python Virtual Env Next, we need to create a virtual environment that our AWS – Lambda function will use to send data to our slack channel. Create a Folder Structure to hold your environment such as:

#Open an Admin Command Prompt Window and issue the following commands :

cd C:\VirtualEnvs
python -m venv SlackNotifier
cd C:\VirtualEnvs\SlackNotifier\Scripts
pip install requests
cd C:\VirtualEnvs
python -m venv SlackNotifier
cd C:\VirtualEnvs\SlackNotifier\Scripts
pip install requests

Next right click inside of C:\VirtualEnvs\SlackNotifier\Lib\site-packages and add a new file called lambda_function.py. Add the following code, add the URL of your slack channel to the URL line.

import json
import requests

def lambda_handler(event, context):
    # TODO implement
    URL = """""" #add your webhookURL
    payload={"text": "A new user has signed up for you app!"}
    r = requests.post(URL,json=payload)
    return {
        'statusCode': 200,
        'body': json.dumps('Message posted to Slack!')

Select the entire contents of site-packages and zip them into “lambda_function.zip” .

Solution – Step 4 Create Super Admin Role in IAM For our lambda function to work we need to assign permissions so that it can access DynamoDB, for this example we will simply create a SuperAdmin role and use that to ensure our function can perform all its duties. For this login to your AWS console and navigate to IAM » Roles.

Create Role

Select Lambda  » Next : Permissions

Assign Admin rights to the role, Click Next : Tags

Click Next : Review

Name your role and click Create Role

Solution – Step 5 Create the Lambda Function Now inside of you AWS console, navigate to the Lambda service. On the AWS Lambda dashboard, click create function.

Choose Author from Scratch, and select Python 3.8 for the Runtime and name “SlackNotifier” and under the choose or create an execution role dropdown select “Use Existing” and select the SuperAdmin role we created earlier.

Once the function is created you will see a screen as follows, all we need to do on this screen is upload the virtual environment that we created earlier. Click Actions » Upload a .zip File

Navigate to lambda_function.zip and upload.

We can setup a test event to make sure the function is posting to our channel correctly:

Now select Test from the Lambda Header menu:

You should get a message in your slack channel :

Now all we need to do is setup DynamoDB and configure it to use this function when new data is added.

Solution – Step 6 Create DynamoDB Table Now in the AWS console navigate to the DynamoDB service and click create table , enter AppUsers as the table name and UserId as the partition key, click Create.

Wait for a few seconds and let the table get created, once it finished, we should have a view as follows:

Solution – Step 7 Enable Streams Now click manage Stream,

Solution – Step 7 Create a trigger for Table Now we create a trigger on the table, navigate to Triggers » Existing Lambda function.

Point it to your existing lambda function:

Solution – Step 8 Test Now that our trigger is setup, lets insert an Item into our dynamoDB table and see what happens. Navigate to Items » Create Item.

Enter a UserId and click Save.

If everything has been configured correctly, you will get a message inside your slack channel indicating a new user has signed up!

Ian Fogelman

Ian Fogelman

My name is Ian Fogelman. I like to develop data driven solutions with SQL Server, Python, .NET and predictive analytics.