Using AWS Lambda to Send SNS Topics in CloudWatch

AWS Lambda enables you to run code without managing a server.  You simply plop in your code and it does the rest (no maintenance, scaling concerns, etc).  The cost is only $0.20 per 1 million requests/month and the first million requests are free each month.

In the previous post, I setup an SNS topic. I’m extending this further so that a node.js function will be triggered in AWS Lambda each time my SNS topic is triggered. This Lambda function will feed metrics into AWS CloudWatch which will allow me to chart/monitor/set alarms against events or patterns with my SNS topic.  A practical use case for this could be understanding event patterns or logging SNS messages (and their contents) sent to your customers.

Creating your Lambda Function

From the Lambda page of the AWS console, select “Create Function”.  From here, we’ll author from scratch.  Below are the inputs I’ve used for this example:
Name: SNSPingerToCloudWatch
Runtime: Node.js 8.10
Role: Choose and existing role
Existing role: lambda_basic_execution

On the page after selecting “Create Function”, we’ll click “SNS” from the “Add Triggers” section and then select our SNS topic in the “Configure Triggers” section.  Then click “Add” and “Save”.  Here’s a screenshot of the final state.

Next, click on your function name (SNSPingerToCloudWatch) in the flow chart and scroll to edit the function code.
The JS we’ll use:

exports.handler = async (event, context) => {
    const message = event.Records[0].Sns.Message;
    console.log('Pinger says:', message);
    return message;

Under Basic Settings, I’ve set the timeout duration to 5 seconds (because that’s the timeout duration I have set in my SNS topic PHP script) You can add descriptions, throttles, etc but I’m leaving those at the defaults.  Here’s a screenshot of my final config for this Lambda function.

Once complete, click “Save” again and then we’re ready to test. I manually fired my SNS topic and jumped over to the “Monitoring” tab of the console. It took a minute or so but I saw my event appear. From here, you can view the log details in CloudWatch, as well.

Publish to AWS SNS Topic With PHP

Simple Notification Service (SNS) is a handy AWS product which enables programmatic publication and subscription to topics.  They can be as simple as email or SMS or involve more complicated services complicated like Lambda, SQS, HTTP, etc.  The write-up below walks through the process end-to-end from installing the AWS PHP SDK to publishing your first message as an SMS/text message.  With a small amount of additional effort, one could quickly expand this to use cases like weather/emergency notifications for office buildings/schools.

The first two steps are one-time setup, walking through AWS PHP SDK installation and IAM Role creation (something new to me).  The remaining steps are a rinse-and-repeat process so future SNS projects should only take minutes to setup.  For this example, I spun up a LAMP instance in Lightsail so my approach is tailored to this default config.

Step 1: Installing/Prepping the AWS PHP SDK

We’re going to do this by using Composer so let’s install that: curl -sS | sudo php Next, we’ll create composer.json to add the right dependency for the AWS SDK: sudo nano composer.json And inside composer.json, we’ll add this requirement:

    "require": {
        "aws/aws-sdk-php": "2.*"
Lastly, we’ll install the dependencies: php composer.phar install The end result should be the presence of ./vendor for your project directory.  This is where the needed libraries will live and an autoloader script which you’ll add as a requirement to your project (noted below).

The next thing we’ll do is setup the the credentials file to house the IAM credentials for this project (and any future projects).  We’ll do this by creating a .aws directory and then creating a credentials file within that directory: sudo mkdir .aws cd ./.aws sudo nano credentials The credentials file structure is outlined in detail here.  Our credentials file will look like: [sns-project] aws_access_key_id = ... aws_secret_access_key = ... Here’s a recording of step 1 as I went through it:

Step 2: Creating the IAM credentials for your project

Now, let’s create the IAM credentials we’ll need to plug into the credentials file.

  1. Navigate to the IAM Console and select “Users”.  Click “Add User“.
  2. Name your project (should match what you’ve loaded in your credentials file- ours is “sns-project”) and check the Programmatic Access box.
  3. Use the existing “AmazonSNSFullAccess” policy and click “Review” to verify everything is correct.
  4. Copy your IAM access key ID and secret IAM access key to notepad – you’ll need these in a moment.  These will be what we plug into our credentials file
  5. Lastly, let’s go back to our SSH window and edit the credentials file to add the aws_access_key_id a d aws_secret_access_key from the console in place the “…” we originally put in the credentials file.

Step 3: Setting up your SNS Topic

We’re finished with the one-time setup portion of this project.  The rest can be a rinse-and-repeat process if you want to setup multiple projects.  For this example, I’m just going to setup a topic to send me SMS/text messages but SNS supports a number of different actions.

Step 4: The PHP Script

This example will just publish a static message but it should be simple enough to expand to your use-cases/projects.  I’ve commented what’s happening inline below but a few callouts…

  • Your profile (“sns-project”) should match what you set in your credentials file.  Example screenshot here.
  • Your region has to match the region in which you created your SNS topic.
  • If you’re using something other than SMS messaging for delivery, you can specify additional parameters in the array below.

putenv('HOME=/home/bitnami'); //Define the home location so can trigger from other locations (cronjobs, for example)
require '../vendor/autoload.php'; //Load the SDK
use Aws\Sns\SnsClient; //Specify  the SNS client from the SDK 
$client = SnsClient::factory(
     'sns-project', //This should match your profile name in the credentials file
     'region' => 'us-west-2', //The region you created your SNS topic (is also noted in your AWS SNS console)
     'version' => '2010-03-31', //The API version to use - no need to modify
$payload = array(
     'TopicArn' => 'arn:aws:sns:us-west-2:189998:sns-project', //The topic ARN from your AWS console
     'Message' => 'This is the content of your text message', //The content of your message.  If you're using email, you can also add Subject to this array to set subject line
     'MessageStructure' => 'string', ); 
try {
      $client->publish( $payload );
      echo 'Success!';
} catch ( Exception $e ) {
      echo "Failure!\n" . $e->getMessage();
From here, you should be good to go!

WordPress Blog on AWS for $5

I’ve been with multiple webhosts over the years (DreamHost, Host Gator, Site5, 1and1, SiteGround, and I’m probably forgetting a few) and even ran a reseller of my own for a several years.  In the past few years, large groups like Endurance International Group have been gobbling up mom-n-pops operations like Site5 and Host Gator and immediately making cuts to customer service and, in some cases, product/service quality.  For running small personal blogs and websites, though, their prices are near impossible to beat. I’ve been wanting to take the plunge into AWS for a while now but my projects and their scale haven’t aligned to make it cost-effective for me, a hobbyist.  In late 2016, however, AWS launched LightSail which enables you to launch a virtual private machine with numerous pre-configured images for as little as five bucks a month.  That’s SSD storage (overkill for this scale of project but still a nice feature), healthy transfer limits, free static IP, and the ease of scale that AWS has built themselves on and the end result is a super nice product that acts as a gateway for enabling full migration to AWS.  After literally two or three minutes of playing, I had already spun up a new LAMP VPS with WordPress pre-installed.  10 minutes later, I’d migrated my blog (this blog) from back to self-hosting and purchased a dedicated domain.  Within an hour, I’d setup processes on seven AWS products and learned that the massive list of AWS products shouldn’t look as daunting as it appears on their landing page.  I put together the guide below to  encourage others with interest and hesitation to take the plunge and try it out…

Launching WordPress on Lightsail

  1. Visit Lightsail and setup an AWS account if you don’t already have one.
  2. Select “Create Instance” and select the WordPress image.
  3. Select your key pair; I suggest you create a new one to keep things isolated.  Unless you plan on using this for things other than WordPress, you won’t need it anyway thanks to the browser-based SSH available in the Lightsail UI.
  4. Select your instance plan.  The cool thing about AWS is they make it incredibly easy to move and scale (up or down).  If you want to change the specs of your instance in the future, just take a snapshot of your existing instance , spin up your new instance, and then migrate the IP — it’s all less than 10 clicks.
  5.  Give a relevant name to your instance and click create.  Within a minute or so, it’ll be live and you’ll be able to attach your free IP.

Registering and pointing a domain name to Lightsail via Route 53

  1. Visit Route 53 and select Domain Registration.  The pricing is very competitive for TLDs and they offer free privacy protection for WhoIs which is a nice bonus.
  2. After completing registration and the request is out of pending status (~5 minutes), go to “Registered Domains” and click on the new domain you just registered.
  3. Click the “Manage DNS” button then select “Create Record Set”.
  4. Flip back to the Lightsail console for your instance and select “Create a DNS zone”
  5. Set your A record for your domain to point to your Lightsail static IP.  You should have a record for your domain with and without the www prefix.  Copy the four nameservers at the bottom of the page.
  6. Back in the Route 53 console, set the nameservers (NS) to the four nameservers you copied from Lightsail and set the TTL to 1 minute before saving.  If you don’t adjust this before saving, your changes will not be recognized until the default TTL has lapsed (which is two days).  Leave the routing policy set to Simple and click Create.
  7. Return to the Lightsail console and copy your public IP.
  8. Return to Route 53 and add two new A records: 1 A record without the www prefix and 1 with the www prefix.  Again, set the TTL to 60 seconds before creating.
After your new domain name propagates, you’ll be ready to go.  Meanwhile, you can finish your WordPress setup via the public IP.

Setting up email with Lightsail and AWS SES

If you don’t plan on sending or receiving email, this isn’t necessary.  You can setup other mail configurations with Lightsail but I’m opting to utilize AWS Simple Email Service (SES) because it’s the easiest and it makes monitoring of metrics simple.  These next few steps will enable you to retrieve forgotten WordPress passwords and receive email notices from your WordPress instance.
  1. Visit the SES page of the AWS console and select Domains from the left menu.
  2. Next, click the “Verify a New Domain” button, enter your domain name, and check the “Generate DKIM Settings” box – you’ll want this to give your mails additional credibility with email service providers (thus reducing your likelihood of being caught in spam filtering).
  3. After clicking “Verify this Domain”, the next page will share the TXT, CNAME, and MX DNS records needed but, because you purchased your domain within the AWS ecosystem, it’ll create those for you when you select “Use Route 53”.
  4. Ensure all four boxes are checked for “Domain Verification Record”, “DKIM Record Set”, “Email Receiving Record”, and “Hosted Zones” then click “Create Record Sets”.  After a couple of minutes, the domain status in SES should reflect “Verified”/”Yes” for status, DKIM, and enabled for sending.
If you don’t plan on sending emails to anyone except yourself (ie password resets and other notifications from your WordPress instance), click “Email Addresses” from the left menu and verify your personal email address.  This will be the only address your instance can send mail to via SES unless you proceed with the following additional steps…  Proceed depending on your needs/desires. By default, SES accounts are in Sandbox mode which prevents sending mail to addresses which aren’t verified.  To get out of Sandbox mode, we need to do a few things to comply with the SES requirements.
  1. Go to “Configure Sets” from the SES left menu and click “Create Configuration Set”.  Give your set some general name (I called mine default), and select “Create Configuration Set” again.
  2. Select “Add Destination” and select “SNS” from the drop down menu.  Side note: SNS (Simple Notification Service) is another AWS product that’s pretty powerful/cool – I don’t discuss it here but you should read more about it.
  3. To get out of Sandbox, you have to have a process for handling bounces and complaints so, at a minimum, check those two boxes and give your destination some name (such as notifyMe).
  4. Select “Create SNS Topic”, give your topic a name (such as emailMe), and hit “Create Topic”.  Save your configuration set.
  5. Go to the Simple Notification Service page from the AWS console and select “Topics” from the left menu.
  6. Select your topic, select “Subscribe to Topic” from the “Actions” drop down menu.  The protocol will be email and the endpoint will be your personal email address.
  7. Lastly, we’ll create a case with AWS support to request a service limit increase for SES.   The configuration set and SNS topic we configured will enable you to select “Yes” for the “I have a process to handle bounces and complaints” question.  Once AWS Support gets back to you, you should now be able to send/receive mail.

Using WordPress plugins to send/receive mail

The rest is really up to personal preference.  Within the SES dashboard, you can view your SMTP settings which you can plug into any number of plugins available within WordPress.  I personally use WP Mail SMTP.   Below is the configuration needed for this particular plugin.
  1. From the plugin configration page within WordPress, the mailer selected should be “Other SMTP”
  2. The SMTP host will be the hostname in your AWS SES dashboard
  3. Encryption will be TLS and port is 587
  4. Authentication should be turned on
  5. The SMTP username and password will come from your AWS SES dashboard by clicking “Create My SMTP Credentials”.  Side note: what you’re actually doing is creating an IAM (Identity Access and Management) role.  IAM is actually yet another AWS product that you’ll be using as part of this project.  Similar to SNS, I won’t go into IAM but it’s also another cool/powerful AWS product.


This should get you fully up and running with a total time investment of less than 30 minutes and an ongoing cost of ~$5 per month.  Personally, the reward is in learning more about the AWS line of products.  Exploring around, you’ll see you can easily tie into other AWS services like creating CloudWatch monitors to monitor uptime/outages, expand your integration with SNS for notification of issues, etc.  Many of these are within the AWS Free Tier, too.  One last side note: you can create a CloudWatch monitor to monitor your costs and trigger an alert to an SNS topic when they breach a threshold.  If you’re playing around, I strongly encourage this as the AWS console doesn’t notify you of costs as you’re clicking away.