DynamoDB to SES Tutorial

AWS's DynamoDB is a NoSQL database that is a popular choice amongst serverless developers for good reason - it scales automatically and can be configured to be truly serverless when its billing mode is set to PAY_PER_REQUEST. But just having some data in a database isn't very useful if you can't do anything with it. That's where services such as AWS's Simple Email Service come in handy.

This tutorial will show you how to populate a DynamoDB Table with links to images, then randomly select one of those images to send in a daily email.

By the end of the tutorial, you will have deployed into your AWS account:

• One AWS Lambda Function that writes links to images in a table from a public API
• A DynamoDB Table that stores image data
• Another AWS Lambda Function that sends a daily email using data from the table
• A CloudWatch Event Timer that triggers the sendEmail Lambda

Each step of the tutorial includes:

1. A gif showing a preview of what you'll be doing in that step
2. Step-by-step written instructions with code examples and screenshots

Tutorial Updates

As we continue to develop Stackery, there may be improvements made to the design of the application. You may notice some differences between current versions, and versions used to record our video guides. Rest assured, the overall functionality of Stackery remains the same.

For the most up-to-date visuals and instructions, please refer to the transcribed versions of the tutorial available below each video guide.

Setup

Project Repositories

The following repositories are referenced throughout this tutorial:

• Dynamo to SES Repository (Completed)

Required Installations

The following software is used in this tutorial:

• Node.js + Node Package Manager (npm)
• The AWS-SDK for Node
• Flickr-SDK, a library for using Flickr's API (requires free Flickr account)

Deploy Sample App

You can deploy the completed example into your own AWS account using these two Stackery CLI commands:

stackery create will initialize a new repo in your GitHub account, initializing it with the contents of the referenced blueprint repository.

stackery create --stack-name 'dynamodb-to-ses' \
--git-provider 'github' \
--blueprint-git-url 'https://github.com/stackery/dynamo-to-ses' 

stackery deploy will deploy the newly created stack into your AWS account.

stackery deploy --stack-name 'dynamo-to-ses' \
--env-name 'development' \
--git-ref 'master'

What We're Building

There are numerous use cases for what we're about to build. We will be populating a database using one function, then using another to send an email at a pre-determined interval that includes data from that database. One real-world example would be a database that keeps a record of new user sign-ups to your application. You could then use the sendDailyEmail function to filter sign-ups by those that occurred in the last 24 hours, and send a daily email to your team listing all of the new sign-ups.

In our example, we will be using the free Flickr API to populate our table with images of servers, then sending a daily email reminder that yes, there are still servers in 'serverless' - we just no longer have to think about them 😉.

The finished stack in Stackery

Resources used

The following are descriptions of the Stackery resources we'll be working with:

• Function : This application will have two Lambda functions: one that writes data to a table, and another that reads data from that table and sends an email.

• Table : The DynamoDB Table our functions will be writing to and reading from. Each function will receive the limited permissions it needs to do its task.

• Timer : A CloudWatch Event Timer configured to trigger the sendDailyEmail function every day at 9am PST.

We'll get to configuring these resources in later parts, for now, we want to create an empty stack to start with.

1. Set up Your Stack

Create a new stack

1. Navigate to Stacks
2. Select Add a Stack in the top right corner
3. Select your Git Hosting Provider
4. Enter dynamodb-to-ses for Stack Name
5. Keep Create New Repo selected for the Repo Source
6. For Organization, select the Git account you want this repository in
7. Keep the Repo Name the same as Stack Name
8. For Stack Blueprint choose 'Blank'
9. Click Add Stack to create an empty stack

Stackery initializes the following blank stack:

Add two functions

First, our dynamodb-to-ses app needs two Function resources.

1. Click the Add Resource button in the top right
2. Select Function and click it twice to add two functions to the canvas
3. Double-click the first Function to open the editing panel
4. Enter writeToTable for the function Name
5. Change the Logical ID to writeToTable
6. Change the Source Path to src/writeToTable
7. Leave the other values as they are
8. Click Save at the bottom to save your function
9. Double-click the second Function to open the editing panel
10. Enter sendDailyEmail for the function Name
11. Change the Logical ID to sendDailyEmail
12. Change the Source Path to src/sendDailyEmail
13. Leave the other values as they are
14. Click Save at the bottom to save your function

Your Dashboard should now look like this:

Add a table

Next you need to add a table to your stack:

1. Click the Add Resource button in the top right
2. Select Table and click or drag and drop it onto the canvas
3. Double-click the Table to open the editing panel
4. Enter ServerTable for the table Name
5. Enter ServerTable for the table Logical ID
6. Leave the other values as they are
7. Click Save at the bottom to save your table

Add a timer

The final resource will be a timer, which triggers the sendDailyEmail function every day at 9 am PST.

1. Click the Add Resource button in the top right
2. Select Timer and click or drag and drop it onto the canvas
3. Double-click the Timer to open the editing panel
4. Enter dailyEmailTrigger for the Display Name
5. Select Cron Expression for Type
6. Enter 0 16 * * ? * for the Cron Expression
7. Click Save at the bottom to save your timer

Connect and commit your resources

Your stack now has all of the resources you will need. The final step before you edit your code is to connect them and commit your changes:

1. Drag a Service Discovery Wire from the endpoint on the right side of the writeToTable function to the endpoint on the left side of the ServerTable table
2. Drag a Service Discovery Wire from the endpoint on the right side of the sendDailyEmail function to the endpoint on the left side of the ServerTable table
3. Drag an Integration Wire from the endpoint on the right side of the dailyEmailTrigger timer to the endpoint on the left side of the sendDailyEmail function
4. Commit your changes by pressing the Commit... button in the sidebar and entering a commit message
5. Click Commit and Push to push your changes to your Git repository

Your dynamodb-to-ses stack should now look like this:

UP NEXT: Get your code from your GitHub repository.

2. Get Code from GitHub

Pull down your code from GitHub

In order to configure our webhook function, we need to be able to edit it on our local machine. Luckily, Stackery makes this easy to do so.

1. If it's not open already, navigate to dynamodb-to-ses in Stacks
2. Click the Git link under the stack name (see screenshot below). This will take you to your Git repository in the browser

3. Clone your repository onto your local machine

You should now have access to your serverless application in your IDE, and your project files should look similar to this:

UP NEXT: Writing the logic for your functions.

3. Write Your Functions

Add writeToTable function code

The first function we'll set up is writeToTable. It will use the flickr-sdk package to grab images from the Flickr API, then the AWS-SDK to write them to the ServerTable table.

1. In your text editor or IDE, open dynamodb-to-ses/src/writeToTable/index.js
2. Replace the existing exports.handler function with the following (see comments for explanations):

const AWS = require('aws-sdk');
const Flickr = require('flickr-sdk');

async function getPhotos () {
  const flickr = new Flickr(process.env.FLICKR_API_KEY);
  // Get photos from the Flickr api
  try {
    // All options: https://www.flickr.com/services/api/flickr.photos.search.html
    const photos = await flickr.photos.search({
      text: 'servers datacenter', // the search text
      sort: 'interestingness-desc', // sort to attempt to reduce spam photos
      content_type: 1, // only photos
      safe_search: 1, // only SFW photos please
      extras: 'url_o', // we want the original image urls
      per_page: 100
    });
    return photos.body.photos.photo;
  }
  catch (error) {
    console.log('Error getting photos');
    console.log(error);
  }
}

exports.handler = async () => {
  // Fetch an array of photo objects
  const photoArray = await getPhotos();
  // Write new items to the ServerTable
  // Duplicate entries will be skipped
  const dynamodb = new AWS.DynamoDB.DocumentClient();
  // We'll be using promises to make sure everything gets written when the Lambda is called
  let promiseArray = [];

  for (let photo of photoArray) {
    const params = {
      TableName: process.env.TABLE_NAME,
      Item: {
        id: photo.id,
        title: photo.title || null,
        url: photo.url_o,
        height: photo.height_o,
        width: photo.width_o
      },
      ConditionExpression: 'attribute_not_exists(id)', // do not overwrite existing entries
      ReturnConsumedCapacity: 'TOTAL'
    };

    const p = dynamodb.put(params)
      .promise()
      .then(() => {
        console.log(`Writing ${photo.id} to table ${process.env.TABLE_NAME}. Sweet!`);
      })
      .catch((error) => {
        console.log(`Error writing ${photo.id} to table ${process.env.TABLE_NAME}. The entry may already exist.`);
        console.log(error.message);
      });
    promiseArray.push(p);
  };

  try {
    await Promise.all(promiseArray);
    console.log('Writing to dynamodb');
  } catch (error) {;
    console.log(error);
  }

  // Return a 200 response if no errors
  const response = {
    statusCode: 200,
    headers: {
      'Content-Type': 'application/json'
    },
    body: 'Success!'
  };

  return response;
};

As we added a dependency to our function, we need to add a package to its package.json file.

3. Open dynamodb-to-ses/src/writeToTable/package.json and paste in the following below the "aws-sdk" line (remember the comma):

"flickr-sdk": "^3.8.0"

Your file should look something like this:

4. Save both files, and add, commit, and push them to your GitHub repository

Add sendDailyEmail function code

The second function will take a random image from the ServerTable table and send an email with it using AWS's Simple Email Service (SES).

1. In your text editor or IDE, open dynamodb-to-ses/src/sendDailyEmail/index.js
2. Replace the existing exports.handler function with the following (see comments for explanations):

const AWS = require('aws-sdk');

exports.handler = async () => {
  // Get server photos from the ServerTable
  const dynamodb = new AWS.DynamoDB.DocumentClient();
  const params = {
    TableName: process.env.TABLE_NAME
  };
  let photos, body, header;
  let allPhotos = [];

  try {
    photos = await dynamodb.scan(params).promise();
    photos.Items.forEach((photo) => allPhotos.push(photo));
    console.log(`Getting data from table ${process.env.TABLE_NAME}. Right on!`);
  } catch (error) {
    console.log(`Error getting data from table ${process.env.TABLE_NAME}. Make sure this function is running in the same environment as the table.`);
    throw new Error(error); // stop execution if data from dynamodb not available
  }
  
  try {
    // Select a random photo of the day
    const dailyPhoto = await getRandomPhoto(allPhotos);
    // Create the email
    const today = new Date();
    body = await generateEmailBody(dailyPhoto, today);
    header = `Daily Server Email`;
    // Send the email
    console.log(`Sending email to ${process.env.TO_EMAIL}.`);
    await sendEmail(header, body);
    console.log(`Email sent`);
  } catch (error) {
    console.log(`Error sending email`);
    console.log(error);
  }

  // Return a 200 response if no errors
  const response = {
    statusCode: 200,
    body: `Email sent. Body:\n${body}`
  };

  return response;
};

// Select a random photo
function getRandomPhoto (photos) {
  return photos[Math.floor(Math.random()*photos.length)];
};

// Make a pretty email body
function generateEmailBody (photo, today) {
  console.log('Generating pretty email');
  const header = `<h1>✨ An Important Reminder ✨</h1>`;
  const subHeader = `<h2>${getPrettyDate(today)}</h2>`;
  const photoSection = `
    <div>
      <h2>Yes, there are still servers in serverless.</h2>
      <h3>Here is one:</h3>
      <img src='${photo.url}' width='500px' alt='${photo.title}'>
      <p>Now that we've gotten that out of the way, let's go build something awesome with <a href="app.stackery.io">Stackery</a>!</p>
    </div>
  `;

  const style = `
    <style>
      body {
        font-family: sans-serif;
        text-align: center;
      }
    </style>
    `;

  return `
    <html>
      <head>${style}</head>
      <body>
        ${header}
        ${subHeader}
        <br/><hr/><br/>
        <div>
          ${photoSection}
        </div>
      </body>
    </html>
  `;
};

// Use AWS SES to send the email
async function sendEmail (subject, body) {
  let params = {
    Destination: {
      ToAddresses: [
        process.env.TO_EMAIL
      ]
    },
    Message: {
      Body: {
        Html: {
          Charset: 'UTF-8',
          Data: body
        }
      },
      Subject: {
        Charset: 'UTF-8',
        Data: subject
      }
    },
    Source: process.env.FROM_EMAIL
  };

  const ses = new AWS.SES();
  await ses.sendEmail(params).promise();
}

// Format the date for the email
function getPrettyDate (date) {
  const options = {  
      weekday: 'long',
      year: 'numeric',
      month: 'short',
      day: 'numeric',
      hour: '2-digit',
      minute: '2-digit'
  };

  return date.toLocaleString('en-us', options);
}

3. Save the file, and add, commit, and push it to your GitHub repository
4. Back in the Stackery Dashboard, you will see a message to refresh the app as changes from your repo have been detected. Click refresh (If this alert does not show for you, simply refresh your browser to display any changes)

UP NEXT: Configuring the permissions and environment variables your stack will need.

4. Configure Permissions and Environment Variables

Configure your Environment Variables

You may have noticed several environment variables in the code above, such as process.env.TABLE_NAME and process.env.FLICKR_API_KEY. In order for our functions to work, Stackery injects the correct values when packaging your code for CloudFormation. That means that we need to set up these variables in the environment(s) you will be deploying to. We will do this back in the Stackery Dashboard in your browser.

1. In the Stackery Dashboard, refresh your stack to make sure you are on your latest commit
2. In the top navigation, choose Environments. You will be taken to your list of environments
3. Click on the name of the environment you will be deploying into
4. In the left sidebar, click the Parameters tab

This is where you will configure all of the parameters you will need for your functions - keeping them out of your public repository. They are stored as a JSON config object.

5. Paste the following in the editor:

{
  "flickrApiKey": "your-key-here",
  "serverEmail": {
    "toEmail": "your.email@domain.com",
    "fromEmail": "your.email@domain.com"
  }
}

6. Replace "your.email@domain.com" with your real email address. For testing, you should use your own email for both the toEmail and fromEmail parameters, and you can change those later when your app is ready for production
7. If you don't already have a Flickr API Key (you don't need a secret key for this app), open the Flickr API site, click the link that says "Apply for your key online now", log in or create an account, choose Apply for a non-commercial key, name your app and write a short description, agree to the TOS, and click Submit. On the next page, copy your application Key and paste it in your environment parameters in Stackery, replacing the your-key-here placeholder
8. Click Save to save your environment parameters

9. Navigate back to Stacks and choose dynamodb-to-ses from your stacks list
10. Click Edit in the sidebar to get back to editing your stack
11. Double-click on the writeToTable function to open the editor panel
12. At the very bottom, under Environment Variables, click the ellipses, and choose Config
13. Enter FLICKR_API_KEY as the Key
14. Enter flickrApiKey as the Value (it should auto-populate from your Environments config)
15. Click Save at the bottom to save your function

16. Double-click on the sendDailyEmail function to open the editor panel
17. At the very bottom, under Environment Variables, click the ellipses, and choose Config
18. Enter TO_EMAIL as the Key
19. Enter serverEmail.toEmail as the Value (it should auto-populate from your Environments config)
20. In the next field, click the ellipses, and choose Config
21. Enter FROM_EMAIL as the Key
22. Enter serverEmail.fromEmail as the Value (it should auto-populate from your Environments config)
23. Click Save at the bottom to save your function

17. Click Commit... in the left sidebar, add a message, and click Commit and Push to push your changes to your Git repository

You do not need to manually configure the TABLE_NAME environment parameter, as Stackery automatically configures it for you when you connect your function to a table with an Integration Wire.

Add SES permissions

In order to be able to send emails using AWS SES, we have to configure and verify the to and from emails you will be using (in the future, you can request permission from AWS to remove this sandboxing restriction, but it will be on by default). We also have to add a new policy in our template.yaml configuration.

1. In your stack edit view, switch the Edit Mode from "Visual" to "Template"

2. Scroll down in the YAML file to the sendDailyEmail function configuration
3. Paste in the following under Policies (be very mindful of the spacing):

        - SESCrudPolicy:
            IdentityName: your.email@domain.com

4. Change your.email@domain.com to the same email you entered in the environment parameters configuration
5. Click Commit... in the left sidebar, add a message, and click Commit and Push to push your changes to your Git repository

The next step will need to take place in the AWS Console. Follow the link to get to your console and make sure you are logged into the same account and region as the environment you plan to deploy to.

1. In the AWS Console, navigate to the Simple Email Service page
2. Click Go to identity management
3. In the left sidebar, choose Email Addresses
4. Click Verify a New Email Address at the top
5. Enter the same email address as you added to your environment parameters, then click Verify This Email Address
6. You will receive a verification email. Click the link and you will see that your email is now verified

UP NEXT: Deploying your stack to AWS.

5. Deploy Your Stack

Now we're ready to deploy our stack for testing. Return to your stack view in the Stackery Dashboard.

1. In the left sidebar, navigate to the Deploy view, and click Prepare new deployment in the same environment in which you stored your environment variables in earlier
2. Click Prepare Deployment. This will take about a minute

3. Once the deployment is prepared, click Deploy. This will take you to the AWS Console

4. In the AWS Console, click Execute in the top right. Deploying your stack will take a few minutes. (You can close the AWS Console once the deployment process has started)

5. Back in the Stackery Dashboard, you will see a notification when your deployment is ready. Click the View in Dashboard link to see your deployed stack

UP NEXT: Populating the table and sending an email.

6. Test Your Functions

Test the writeToTable function

In this step, we will trigger the writeToTable function to make it populate the ServerTable with images from Flickr.

1. In the View page for your stack, double-click the writeToTable function
2. Click the View in AWS Console button near the top. You will be taken to the Lambda page for that function

3. Click the Test button at the top right. You will be prompted to create a test event.
4. In the modal, give the event a name such as test and leave the values as they are, then scroll down to click Create

5. Click the Test button again

6. You should see a message below saying "Execution result: succeeded(logs)". (If this is not the case, see the Troubleshooting section at the end)
7. Click the "Details" arrow to see more. It should look like this:

8. You can see the log output, which will show all of your events as well as billing and execution details
9. Close the AWS Console and return to Stackery

View the ServerTable

When you manually invoked the writeToTable function, it populated the ServerTable table. Now we'd like to take a look at it.

1. Close the function detail view if it's open, and double-click on the ServerTable node
2. Click the View in AWS Console button near the top. You will be taken to the DynamoDB page for that table
3. In the AWS Console, click the Items tab at the top
4. You should see a list of 100 items - those are your server images!

Test the sendDailyEmail function

Now that we have a table to choose images from, let's send our test email! Return to Stackery for this step.

1. Close the table detail view if it's open, and double-click on the sendDailyEmail node
2. Click the View in AWS Console button near the top. You will be taken to the Lambda page for that function
3. Click the Test button at the top right. You will be prompted to create another test event.
4. In the modal, give the event a name such as test and leave the values as they are, then scroll down to click Create
5. Click the Test button again
6. Once again, you should see a message below saying "Execution result: succeeded(logs)". You should also receive an email!
7. Check your email. You should have received something like this:

Awesome! You (or whomever you choose to send your email to) will now get a daily reminder that indeed, there are still servers in serverless!

Expanding on this Tutorial

You now have a serverless stack that can write data to a table, get data from that table, and send an email - imagine the possibilities!

Here are some ways of expanding on your dynamodb-to-ses application:

• Use a Git webhook to trigger a function that writes an event to your table every time a designated repository is updated. Then, you can send a daily or weekly email with all the changes made to that repository in that timeframe - instant changelog!
• Use DynamoDB as your CMS for a weekly email. You can use a serverless web form to populate another table with email addresses to send to
• Populate a table with pictures of your kids/cat/dog/ferret, and send an email to family members each time a new item is added

There's a lot more you can do with Stackery, so keep building!

Troubleshooting

Common errors you may come across when following along with this tutorial.

Failure to prepare your stack

If you try to prepare in an environment that is not configured with the correct environment variables, you will see the following error in Stackery:

Follow Step 4 above to correctly configure the environment you plan to deploy into.

The conditional request failed error when writing to DynamoDB

The writeToTable function is set up to not overwrite existing items. If you would prefer to overwrite items in your use case, simply remove the condition

ConditionExpression: 'attribute_not_exists(id)'

from line 44 of the writeToTable function.

See the AWS SDK DynamoDB docs for more options when writing to and reading from DynamoDB tables.