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App

The App construct extends cdk.App and is used internally by SST to:

  • Automatically prefix stack names with the stage and app name
  • Deploy the entire app using the same AWS profile and region

It is made available as the app in the stacks() callback in sst.config.ts of your SST app.

sst.config.ts
export default {
  config(input) {
    return {
      name: "myapp",
      region: "us-east-1",
    };
  },
  stacks(app) {},
} satisfies SSTConfig;

Since it is initialized internally, the props that are passed to App cannot be changed.

Examples​

Accessing app properties​

The properties of the app can be accessed in the sst.config.ts as:

stacks(app) {
  app.name;
  app.stage;
  app.region;
  app.account;
}

Specifying default function props​

You can also use addDefaultFunctionPermissions, addDefaultFunctionEnv, and addDefaultFunctionLayers to progressively add more permissions, environment variables, and layers to the defaults. These can be called multiple times and from anywhere.

sst.config.ts
stacks(app) {
  app.setDefaultFunctionProps({
    timeout: 20,
    memorySize: 512,
    runtime: "go1.x",
    environment: { TABLE_NAME: "NOTES_TABLE" },
  });

  // Start adding stacks
}

Or if you need to access the Stack scope, you can pass in a callback.

sst.config.ts
import { StringParameter } from "aws-cdk-lib/aws-ssm";

stacks(app) {
  app.setDefaultFunctionProps((stack) => ({
    timeout: 20,
    memorySize: 512,
    runtime: "go1.x",
    environment: {
      API_KEY: StringParameter.valueFromLookup(stack, "my_api_key"),
    },
  }));

  // Start adding stacks
}

Updating default function props​

You can also use addDefaultFunctionPermissions, addDefaultFunctionEnv, and addDefaultFunctionLayers to progressively add more permissions, environment variables, and layers to the defaults. These can be called multiple times and from anywhere.

However, they only affect the functions that are created after the call.

sst.config.ts
stacks(app) {
  app.stack(StackA)

  app.addDefaultFunctionEnv({
    TABLE_NAME: "NOTES_TABLE"
  });

  app.addDefaultFunctionPermissions(["s3"]);

  app.addDefaultFunctionLayers([mylayer]);

  app.stack(StackB)

  // Add more stacks
}

So in the above example, the addDefaultFunctionPermissions and addDefaultFunctionEnv calls will only impact the functions in StackB.

You can also use the Stack's setDefaultFunctionProps to update these for a specific stack.

Setting a default removal policy​

You can set a removal policy to apply to all the resources in the app. This is useful for ephemeral environments that need to clean up all their resources on removal.

sst.config.ts
stacks(app) {
  // Remove all resources when the dev stage is removed
  if (app.stage === "dev") {
    app.setDefaultRemovalPolicy("destroy");
  }

  // Add stacks
}

Note that, the setDefaultRemovalPolicy method isn't meant to be used for production environments.

Properties​

An instance of App has the following properties.

account​

Type : string

The AWS account the app is being deployed to. This comes from the IAM credentials being used to run the SST CLI.

defaultRemovalPolicy​

Type : undefined | "destroy" | "retain" | "snapshot" | "retain-on-update-or-delete"

isActiveStack?​

Type : (string) => boolean

local​

Type : boolean

Whether or not the app is running locally under sst dev

mode​

Type : "dev" | "deploy" | "remove"

Whether the app is running locally under start, deploy or remove

name​

Type : string

The name of your app, comes from the name in your sst.config.ts

region​

Type : string

The region the app is being deployed to. If this is not specified as the --region option in the SST CLI, it'll default to the region in your sst.config.ts.

stage​

Type : string

The stage the app is being deployed to. If this is not specified as the --stage option, it'll default to the stage configured during the initial run of the SST CLI.

Methods​

An instance of App has the following methods.

addDefaultFunctionBinding​

addDefaultFunctionBinding(bind)

Parameters

  • bind Array<BindingResource>

Binds additional default resources to be applied to all Lambda functions in the app.

app.addDefaultFunctionBinding([STRIPE_KEY, bucket]);

addDefaultFunctionEnv​

addDefaultFunctionEnv(environment)

Parameters

  • environment Record<string, string>

Adds additional default environment variables to be applied to all Lambda functions in the app.

app.addDefaultFunctionEnv({
  "MY_ENV_VAR": "my-value"
})

addDefaultFunctionLayers​

addDefaultFunctionLayers(layers)

Parameters

Adds additional default layers to be applied to all Lambda functions in the stack.

addDefaultFunctionPermissions​

addDefaultFunctionPermissions(permissions)

Parameters

Adds additional default Permissions to be applied to all Lambda functions in the app.

app.addDefaultFunctionPermissions(["s3"])

finish​

finish()

logicalPrefixedName​

logicalPrefixedName(logicalName)

Parameters

  • logicalName string

Use this method to prefix resource names in your stacks to make sure they don't thrash when deployed to different stages in the same AWS account. This method will prefix a given resource name with the stage and app name. Using the format ${stage}-${name}-${logicalName} .

console.log(app.logicalPrefixedName("myTopic"));

// dev-my-app-myTopic

registerTypes​

registerTypes(c)

Parameters

  • c SSTConstruct

setDefaultFunctionProps​

setDefaultFunctionProps(props)

Parameters

The default function props to be applied to all the Lambda functions in the app. These default values will be overridden if a Function sets its own props. This needs to be called before a stack with any functions have been added to the app.

app.setDefaultFunctionProps({
  runtime: "nodejs20.x",
  timeout: 30
})

setDefaultRemovalPolicy​

setDefaultRemovalPolicy(policy)

Parameters

  • policy "destroy" | "retain" | "snapshot" | "retain-on-update-or-delete"

The default removal policy that'll be applied to all the resources in the app. This can be useful to set ephemeral (dev or feature branch) environments to remove all the resources on deletion.

danger

Make sure to not set the default removal policy to DESTROY for production environments.

app.setDefaultRemovalPolicy(app.mode === "dev" ? "destroy" : "retain")