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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 this stack needs to be deployed.
By default, if you don't specify an environment when you define a stack, the stack
is said
to be environment agnostic. This means that AWS CloudFormation templates which are
synthesized from this
stack will try to use deploy-time resolution on environment-related attributes such
as
stack.account, stack.region, and
stack.availablityZones. When using cdk deploy to
deploy environment-agnostic stacks, the CLI uses the default CLI environment configuration
to
determine where to deploy this stack. The AWS CDK CLI follows a protocol similar to
the AWS CLI
for determining which AWS credentials to use when performing operations against your
AWS
account. See AWS CDK Command Line Interface (cdk) for details.
For production systems, we recommend that you explicitly specify the environment
for each stack in your app using the env property.
The following example specifies two environments used in two different stacks.
const envEU = { account: '2383838383', region: 'eu-west-1' }; const envUSA = { account: '8373873873', region: 'us-west-2' }; new MyFirstStack(this, 'first-stack-us', { env: envUSA, encryption: false }); new MyFirstStack(this, 'first-stack-eu', { env: envEU, encryption: true });
By explicitly specifying the target account and Region, the AWS CDK CLI ensures that
you
only deploy this stack to the desired target and deployment if the configured credentials
are
not aligned. To deploy stacks to multiple accounts or different Regions, you must
set the
correct credentials or Region each time you run a cdk deploy
STACK command.
You can use the CDK_DEFAULT_ACCOUNT and CDK_DEFAULT_REGION
environment variables to explicitly associate a stack with the default CLI environment,
as
shown in the following example. This is a common practice for development stacks that
you want
to include in your app, and have each developer use their own account.
new MyDevStack(this, 'dev', { env: { account: process.env.CDK_DEFAULT_ACCOUNT, region: process.env.CDK_DEFAULT_REGION } });
Note
There is a distinction between not specifying the env property at
all and specifying CDK_DEFAULT_ACCOUNT and CDK_DEFAULT_REGION.
The former implies that the stack should synthesize an environment-agnostic template.
This
means that constructs that are defined in such a stack cannot make assumptions about
their
environment. For example, you can't write code like if (stack.region ===
'us-east-1') or use framework facilities like Vpc.fromLookup, which need to query your AWS account. When specifying
CDK_DEFAULT_ACCOUNT and CDK_DEFAULT_REGION, you tell the
stack that it will be deployed in the account and Region as configured in the CLI
at the
time of synthesis. This means that the synthesized template could be different on
different
machines, users, or sessions. This might be acceptable for use cases like development
stacks, but would be an anti-pattern for production stacks.
