The Complete Guide to Adding AWS Resources to Your Amplify Project
Tags: aws, serverless
Published: 2021-12-13 18:03:24


![image.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638891565224/1Xa3SzL8f.png)

During  [Dr. Werner Vogel's re:Invent keynote](https://www.youtube.com/watch?v=8_Xs8Ik0h1w), the point was made that AWS has a ton of services--each one designed to solve a customer pain point.

 [AWS Amplify](https://docs.amplify.aws) composes some of those services together to create a framework designed for today's professional frontend developer. These services can be added with a CLI command. For example, to add a GraphQL API or REST API, one would type.

`amplify add api`

We at Amplify integrate core services needed to build production apps, but the reality is that today's applications need a wide variety of services. One initial solution, was to put all 175+ services in the CLI 😅

I'm happy to say we have a better way:

`amplify add custom`

This command will scaffold out files using  [AWS Cloud Development Kit](https://aws.amazon.com/cdk/) (CDK) or AWS CloudFormation.  You can then use this stack to add whatever services you like. In this post, we'll walk through what that experience is like so you can feel comfortable adding any AWS resource to your next project,  not just [the ones offered directly through the CLI](https://docs.amplify.aws/cli/) .

## Adding a custom resource

As mentioned, both CDK and CloudFormation are supported, but my opinion is that most frontend developers will enjoy writing TypeScript to generate their infrastructure, so that's what we'll be using in this post. 

After running `amplify add custom` and following the prompts, Amplify will generate our CDK stack.

![CLI output where a user has confirmed they are using CDK and selected yes to the prompts](https://cdn.hashnode.com/res/hashnode/image/upload/v1638978503725/PiK4HVO8l.png)

If you've worked in CDK with TypeScript before, you should feel right at home since the generated files are very similar to what you would get when running 

```js
cdk init --template sample-app --language typescript
```

The key differences is that we include a few more examples for folks to get started, and a few Amplify helpers to easily connect Amplify with your CDK backend.

After deleting the commented examples for now, the following screenshot is what is left:

![a CDK stack that is very similar to what is generated when running cdk init](https://cdn.hashnode.com/res/hashnode/image/upload/v1638979030116/MHwL2vG6lN.png)

## Adding an SNS Topic and SQS 

Let's say you wanted to [send a text message to a group of interested individuals](https://blog.focusotter.com/send-an-sms-to-customers-using-react-and-aws-amplify). To avoid bottling up the downstream service, we'll also add an SQS Queue so messages can be picked up in batches.

This scenario is exactly what we provide out of the box as one of our commented out examples!

![An SNS Topic and SQS queue being created and added together in a CDK project from Amplify](https://cdn.hashnode.com/res/hashnode/image/upload/v1638981331864/h-hf6IhVl.png)

Keep in mind that any resource that you see in the  [CDK docs](https://docs.aws.amazon.com/cdk/api/latest/) is fair game to be added.

## Understanding Amplify helpers

Now that we understand how resources can be added, let's look at some of the extra benefits Amplify provides.

**AmplifyHelpers**: We automatically install a package called `@aws-amplify/cli-extensibility-helper`. 

This currently contains two methods: `getProjectInfo` and `addResourceDependency`. We'll chat about adding resources dependencies in a bit, but let's first explore the available project info.

Calling this method currently provides two properties: `envName` and `projectName`.

![envName and projectName being show via intellisense](https://cdn.hashnode.com/res/hashnode/image/upload/v1638984433953/pOlzlAf3r.png)

The `envName` corresponds to the current Amplify environment. By default, this is `dev`, though by running `amplify env add <envName>` [users can add branches to their backends](https://docs.amplify.aws/cli/teams/overview/) , much like when working in git.

> 🚨Due to the lifecycle of when the environment name gets populated, the `envName` here is to be used for conditional checks only, not for naming resources:

```js
if(AmplifyHelpers.getProjectInfo().envName === 'prod') {
  // create an IAM role to allow access to a prod account
}
```
Additionally, the `projectName` is the name specified in the CLI when first running `amplify add custom` (see the first screenshot). As we saw when we created our resources, this is great for project organization:

![resource naming with the correct Amplify environment](https://cdn.hashnode.com/res/hashnode/image/upload/v1638985245133/RVgGjxJqV.png)

> 🗒️Note that the above screenshot also shows the correct way to pull in the Amplify environment when naming resources.

## Working with Amplify generated resources

In addition to `AmplifyHelpers.getProjectInfo()`, let's look at `AmplifyHelpers.addResourceDependency()`.

This method will bring in resources that we generated with the Amplify CLI. 

> 🗒️ It's worth noting that when running `amplify add custom`, example 3 of the commented boilerplate code provides this function by default.

Because we're in TypeScript, our `retVal` variable is already typed to reference our Amplify resources:

![amplify resources typed objects](https://cdn.hashnode.com/res/hashnode/image/upload/v1638988680956/ooaE55wfl.png)

If by chance you just pushed up some resources and aren't seeing values like `Arn` and `region`, running `amplify build` will regenerate this file.

Within the `addResourceDependency` function, we can specify which of our Amplify resources we would like access to by passing in an array, where each object in it has a `category` and `resourceName` key.

Keep in mind that what we have so far is a type representation of what we need (`int`, `string`, etc). So from here, we can use a CDK helper method to extract the actual value:

```js
const authArn = cdk.Fn.ref(retVal.auth.amplifystripestarter9420c337.UserPoolArn)
```

![complete flow of adding resources and extracting their values](https://cdn.hashnode.com/res/hashnode/image/upload/v1638989231513/lnQF7hGWR.png)


## Accessing custom stacks in Lambda

To look at the other side of the fence, suppose we ran `amplify push` and deployed our custom stack. Then we add a Lambda via `amplify add function` to our project. In this case, we also need to grant access for our Lambda to call SNS.

To accomplish this, we can take advantage of the `custom-policies.json` file that we now generate with every Lambda created:

```js
[
	{
		"Action": ["SNS:Publish"],
		"Resource": ["arn:aws:sns:*:*:mySNSTopic-${env}"]
	}
]
```

Note that we support wildcards for the region and account number. Additionally, we interpolate the Amplify environment by using the `${env}` syntax.

## Conclusion

In this example, we took a peek at how to subscribe an SQS Queue to an SNS Topic, but the learnings went far beyond that. By adding custom resources with the CDK, pulling in existing resources created with the Amplify CLI, and updating policies so Lambda functions have permissions to call our external resources, users now have the ability to create truly rich applications while minimizing time spent in the AWS Console.

This is just one of aspects of Amplify's new extensibility releases. For a rundown of all the new enhancements and a glimpse into the posts I'll be releasing, checkout my blog post over on A Cloud Guru that covers  [5 new Amplify features to take your app to any scale](https://acloudguru.com/blog/engineering/5-new-amplify-features-to-take-your-app-to-any-scale).