Environments

Each Stack instance in your AWS CDK app is explicitly or implicitly associated with an environment (env). An environment is the target AWS account and AWS Region into which the stack is intended to be deployed.

If you don't specify an environment when you define a stack, the stack is said to be environment-agnostic. AWS CloudFormation templates synthesized from such a stack will try to use deploy-time resolution on environment-related attributes such as stack.account, stack.region, and stack.availablityZones (Python: availability_zones).

Note

In an environment-agnostic stack, any constructs that use availability zones will see two of them. This allows the stack to be deployed to almost any region, since nearly all regions have at least two availability zones. The only exception is Osaka (ap-northeast-3), which has one.

When using cdk deploy to deploy environment-agnostic stacks, the AWS CDK CLI uses the specified AWS CLI profile (or the default profile, if none is specified) to determine where to deploy. The AWS CDK CLI follows a protocol similar to the AWS CLI to determine which AWS credentials to use when performing operations against your AWS account. See AWS CDK Toolkit (cdk) for details.

For production stacks, we recommend that you explicitly specify the environment for each stack in your app using the env property. The following example specifies different environments for its two different stacks.

TypeScript

const envEU  = { account: '2383838383', region: 'eu-west-1' };
const envUSA = { account: '8373873873', region: 'us-west-2' };

new MyFirstStack(app, 'first-stack-us', { env: envUSA, encryption: false });
new MyFirstStack(app, 'first-stack-eu', { env: envEU, encryption: true  });

Python

env_EU = core.Environment(account="8373873873", region="eu-west-1")
env_USA = core.Environment(account="2383838383", region="us-west-2")

MyFirstStack(app, "first-stack-us", env=env_USA, encryption=False)
MyFirstStack(app, "first-stack-eu", env=env_EU, encryption=True)

Java

public class MyApp {

    // Helper method to build an environment
    static Environment makeEnv(String account, String region) {
        return Environment.builder()
                .account(account)
                .region(region)
                .build();
    }

    public static void main(final String argv[]) {
        App app = new App();

        Environment envEU = makeEnv("8373873873", "eu-west-1");
        Environment envUSA = makeEnv("2383838383", "us-west-2");
        
        new MyFirstStack(app, "first-stack-us", StackProps.builder()
                .env(envUSA).build());
        new MyFirstStack(app, "first-stack-eu", StackProps.builder()
                .env(envEU).build());
 
        app.synth();
    }
}

C#

Amazon.CDK.Environment makeEnv(string account, string region)
{
    return new Amazon.CDK.Environment
    {
        Account = account,
        Region = region
    };
}

var envEU = makeEnv(account: "8373873873", region: "eu-west-1");
var envUSA = makeEnv(account: "2383838383", region: "us-west-2");

new MyFirstStack(app, "first-stack-us", new StackProps { Env=envUSA });
new MyFirstStack(app, "first-stack-eu", new StackProps { Env=envEU });

When you hard-code the target account and region as above, the stack will always be deployed to that specific account and region. To make the stack deployable to a different target, but to determine the target at synthesis time, your stack can use two environment variables provided by the AWS CDK CLI: CDK_DEFAULT_ACCOUNT and CDK_DEFAULT_REGION. These variables are set based on the AWS profile specified using the --profile option, or the default AWS profile if you don't specify one.

The following code fragment shows how to access the account and region passed from the AWS CDK CLI in your stack.

TypeScript

Access environment variables via the process object.

Note

TypeScript users must install the DefinitelyTyped NodeJS module with NPM to be able to use process. cdk init now installs this module for you, but if you are working with a project created before it was added, or didn't set up your project using cdk init, install it manually.

npm install @types/node

new MyDevStack(app, 'dev', { 
  env: { 
    account: process.env.CDK_DEFAULT_ACCOUNT, 
    region: process.env.CDK_DEFAULT_REGION 
}});

Python

Use the os module's environ dictonary to access environment variables.

import os
MyDevStack(app, "dev", env=core.Environment(
    account=os.environ["CDK_DEFAULT_ACCOUNT"],
    region=os.environ["CDK_DEFAULT_REGION"]))

Java

Use System.getenv() to get the value of an environment variable.

public class MyApp {

    // Helper method to build an environment
    static Environment makeEnv(String account, String region) {
        account = (account == null) ? System.getenv("CDK_DEFAULT_ACCOUNT") : account;
        region = (region == null) ? System.getenv("CDK_DEFAULT_REGION") : region;

        return Environment.builder()
                .account(account)
                .region(region)
                .build();
    }

    public static void main(final String argv[]) {
        App app = new App();

        Environment envEU = makeEnv(null, null);
        Environment envUSA = makeEnv(null, null);
        
        new MyDevStack(app, "first-stack-us", StackProps.builder()
                .env(envUSA).build());
        new MyDevStack(app, "first-stack-eu", StackProps.builder()
                .env(envEU).build());
 
        app.synth();
    }
}

C#

Use System.Environment.GetEnvironmentVariable() to get the value of an environment variable.

Amazon.CDK.Environment makeEnv(string account=null, string region=null)
{
    return new Amazon.CDK.Environment
    {
        Account = account ?? System.Environment.GetEnvironmentVariable("CDK_DEFAULT_ACCOUNT"),
        Region = region ?? System.Environment.GetEnvironmentVariable("CDK_DEFAULT_REGION")
    };
}

new MyDevStack(app, "dev", new StackProps { Env = makeEnv() });

The AWS CDK distinguishes between not specifying the env property at all and specifying it using CDK_DEFAULT_ACCOUNT and CDK_DEFAULT_REGION. The former implies that the stack should synthesize an environment-agnostic template. Constructs that are defined in such a stack cannot use any information about their environment. For example, you can't write code like if (stack.region === 'us-east-1') or use framework facilities like Vpc.fromLookup (Python: from_lookup), which need to query your AWS account.

When you pass in your environment using CDK_DEFAULT_ACCOUNT and CDK_DEFAULT_REGION, the stack will be deployed in the account and Region determined by the AWS CDK CLI at the time of synthesis. This allows environment-dependent code to work, but it also means that the synthesized template could be different based on the machine, user, or session under which it is synthesized. This behavior is often acceptable or even desirable during development, but it would probably be an anti-pattern for production use.

You can set env however you like, using any valid expression. For example, you might write your stack to support two additional environment variables to let you override the account and region at synthesis time. We'll call these CDK_DEPLOY_ACCOUNT and CDK_DEPLOY_REGION here, but you could name them anything you like, as they are not set by the AWS CDK. In the following stack's environment, we use our alternative environment variables if they're set, falling back to the default environment provided by the AWS CDK if they are not.

TypeScript

new MyDevStack(app, 'dev', { 
  env: { 
    account: process.env.CDK_DEPLOY_ACCOUNT || process.env.CDK_DEFAULT_ACCOUNT, 
    region: process.env.CDK_DEPLOY_REGION || process.env.CDK_DEFAULT_REGION 
}});

Python

MyDevStack(app, "dev", env=core.Environment(
    account=os.environ.get("CDK_DEPLOY_ACCOUNT", os.environ["CDK_DEFAULT_ACCOUNT"]),
    region=os.environ.get("CDK_DEPLOY_REGION", os.environ["CDK_DEFAULT_REGION"])

Java

public class MyApp {

    // Helper method to build an environment
    static Environment makeEnv(String account, String region) {
        account = (account == null) ? System.getenv("CDK_DEPLOY_ACCOUNT") : account;
        region = (region == null) ? System.getenv("CDK_DEPLOY_REGION") : region;
        account = (account == null) ? System.getenv("CDK_DEFAULT_ACCOUNT") : account;
        region = (region == null) ? System.getenv("CDK_DEFAULT_REGION") : region;

        return Environment.builder()
                .account(account)
                .region(region)
                .build();
    }

    public static void main(final String argv[]) {
        App app = new App();

        Environment envEU = makeEnv(null, null);
        Environment envUSA = makeEnv(null, null);
        
        new MyDevStack(app, "first-stack-us", StackProps.builder()
                .env(envUSA).build());
        new MyDevStack(app, "first-stack-eu", StackProps.builder()
                .env(envEU).build());
 
        app.synth();
    }
}

C#

Amazon.CDK.Environment makeEnv(string account=null, string region=null)
{
    return new Amazon.CDK.Environment
    {
        Account = account ??
            System.Environment.GetEnvironmentVariable("CDK_DEPLOY_ACCOUNT") ??
            System.Environment.GetEnvironmentVariable("CDK_DEFAULT_ACCOUNT"),
        Region = region ?? 
            System.Environment.GetEnvironmentVariable("CDK_DEPLOY_REGION") ??
            System.Environment.GetEnvironmentVariable("CDK_DEFAULT_REGION")
    };
}

new MyDevStack(app, "dev", new StackProps { Env = makeEnv() });

With your stack's environment declared this way, you can now write a short script or batch file like the following to set the variables from command line arguments, then call cdk deploy.

Linux/Mac OS X

#!/bin/bash
# cdk-deploy-to.sh
export CDK_DEPLOY_ACCOUNT=$1
shift
export CDK_DEPLOY_REGION=$1
shift
cdk deploy "$@"

Windows

@echo off
rem cdk-deploy-to.bat
set CDK_DEPLOY_ACCOUNT=%1
shift
set CDK_DEPLOY_REGION=%1
shift
cdk deploy %*

Then you can write additional scripts that call that script to deploy to specific environments (even multiple environments per script):

Linux/Mac OS X

#!/bin/bash
# cdk-deploy-to-test.sh
bash cdk-deploy-to.sh 123457689 us-east-1 "$@"

Windows

@echo off
rem cdk-deploy-to-test.bat
cdk-deploy-to 135792469 us-east-1 %*

When deploying to multiple environments, consider whether you want to continue deploying to other environments after a deployment fails. The following example avoids deploying to the second production environment if the first doesn't succeed.

Linux/Mac OS X

#!/bin/bash
# cdk-deploy-to-prod.sh
bash cdk-deploy-to.sh 135792468 us-west-1 "$@" || exit
bash cdk-deploy-to.sh 246813579 eu-west-1 "$@"

Windows

@echo off
rem cdk-deploy-to-prod.bat
cdk-deploy-to 135792469 us-west-1 %* || goto :eof
cdk-deploy-to 245813579 eu-west-1 %*

Developers would continue to use the normal cdk deploy command to deploy to their own AWS environments.