This is the AWS CDK v2 Developer Guide. The older CDK v1 entered
maintenance on June 1, 2022 and will now receive only critical bug fixes and security patches.
New features will be developed for CDK v2 exclusively. Support for CDK v1 will
end entirely on June 1, 2023.
Resources
As described in Constructs, the AWS CDK provides a rich class library of
constructs, called AWS constructs, that represent all AWS
resources.
To create an instance of a resource using its corresponding construct, pass in the scope as the first argument,
the logical ID of the construct, and a set of configuration properties (props). For example, here's how to create an
Amazon SQS queue with AWS KMS encryption using the sqs.Queue construct from the AWS Construct Library.
- TypeScript
-
import * as sqs from '@aws-cdk/aws-sqs';
new sqs.Queue(this, 'MyQueue', {
encryption: sqs.QueueEncryption.KMS_MANAGED
});
- JavaScript
-
const sqs = require('@aws-cdk/aws-sqs');
new sqs.Queue(this, 'MyQueue', {
encryption: sqs.QueueEncryption.KMS_MANAGED
});
- Python
-
import aws_cdk.aws_sqs as sqs
sqs.Queue(self, "MyQueue", encryption=sqs.QueueEncryption.KMS_MANAGED)
- Java
-
import software.amazon.awscdk.services.sqs.*;
Queue.Builder.create(this, "MyQueue").encryption(
QueueEncryption.KMS_MANAGED).build();
- C#
-
using Amazon.CDK.AWS.SQS;
new Queue(this, "MyQueue", new QueueProps
{
Encryption = QueueEncryption.KMS_MANAGED
});
Some configuration props are optional, and in many cases have default values. In some cases,
all props are optional, and the last argument can be omitted entirely.
Resource attributes
Most resources in the AWS Construct Library expose attributes, which are resolved at deployment
time by AWS CloudFormation. Attributes are exposed in the form of properties on the resource classes with
the type name as a prefix. The following example shows how to get the URL of an Amazon SQS queue
using the queueUrl
(Python: queue_url
) property.
- TypeScript
-
import * as sqs from '@aws-cdk/aws-sqs';
const queue = new sqs.Queue(this, 'MyQueue');
const url = queue.queueUrl; // => A string representing a deploy-time value
- JavaScript
-
const sqs = require('@aws-cdk/aws-sqs');
const queue = new sqs.Queue(this, 'MyQueue');
const url = queue.queueUrl; // => A string representing a deploy-time value
- Python
-
import aws_cdk.aws_sqs as sqs
queue = sqs.Queue(self, "MyQueue")
url = queue.queue_url # => A string representing a deploy-time value
- Java
-
Queue queue = new Queue(this, "MyQueue");
String url = queue.getQueueUrl(); // => A string representing a deploy-time value
- C#
-
var queue = new Queue(this, "MyQueue");
var url = queue.QueueUrl; // => A string representing a deploy-time value
See Tokens for information about how the AWS CDK encodes deploy-time
attributes as strings.
Referencing resources
Many AWS CDK classes require properties that are AWS CDK resource objects (resources). For
example, an Amazon ECS resource requires a reference to the cluster on which it runs. An Amazon CloudFront
distribution requires a reference to the bucket containing the source code. To satisfy these
requirements, you can refer to a resource in one of two ways:
-
By passing a resource defined in your CDK app, either in the same stack or in a
different one
-
By passing a proxy object referencing a resource defined in your AWS account,
created from a unique identifier of the resource (such as an ARN)
If a construct property represents another AWS construct, its type is that of the
interface type of that construct. For example, the Amazon ECS service takes a property
cluster
of type ecs.ICluster
; the CloudFront distribution takes a
property sourceBucket
(Python: source_bucket
) of type
s3.IBucket
.
You can directly pass any resource object of the proper type defined in the same AWS CDK
app. The following example defines an Amazon ECS cluster and then uses it to define an Amazon ECS
service.
- TypeScript
-
const cluster = new ecs.Cluster(this, 'Cluster', { /*...*/ });
const service = new ecs.Ec2Service(this, 'Service', { cluster: cluster });
- JavaScript
-
const cluster = new ecs.Cluster(this, 'Cluster', { /*...*/ });
const service = new ecs.Ec2Service(this, 'Service', { cluster: cluster });
- Python
-
cluster = ecs.Cluster(self, "Cluster")
service = ecs.Ec2Service(self, "Service", cluster=cluster)
- Java
-
Cluster cluster = new Cluster(this, "Cluster");
Ec2Service service = new Ec2Service(this, "Service",
new Ec2ServiceProps.Builder().cluster(cluster).build());
- C#
-
var cluster = new Cluster(this, "Cluster");
var service = new Ec2Service(this, "Service", new Ec2ServiceProps { Cluster = cluster });
Referencing resources in a different stack
You can refer to resources in a different stack as long as they are defined in the same
app and are in the same AWS account and Region. The following pattern is generally
used:
-
Store a reference to the construct as an attribute of the stack that produces the
resource. (To get a reference to the current construct's stack, use
Stack.of(this)
.)
-
Pass this reference to the constructor of the stack that consumes the resource as a
parameter or a property. The consuming stack then passes it as a property to any
construct that needs it.
The following example defines a stack stack1
. This stack defines an Amazon S3
bucket and stores a reference to the bucket construct as an attribute of the stack. Then the
app defines a second stack, stack2
, which accepts a bucket at instantiation.
stack2
might, for example, define an AWS Glue Table that uses the bucket for data
storage.
- TypeScript
-
const prod = { account: '123456789012', region: 'us-east-1' };
const stack1 = new StackThatProvidesABucket(app, 'Stack1', { env: prod });
// stack2 will take a property { bucket: IBucket }
const stack2 = new StackThatExpectsABucket(app, 'Stack2', {
bucket: stack1.bucket,
env: prod
});
- JavaScript
-
const prod = { account: '123456789012', region: 'us-east-1' };
const stack1 = new StackThatProvidesABucket(app, 'Stack1', { env: prod });
// stack2 will take a property { bucket: IBucket }
const stack2 = new StackThatExpectsABucket(app, 'Stack2', {
bucket: stack1.bucket,
env: prod
});
- Python
-
prod = core.Environment(account="123456789012", region="us-east-1")
stack1 = StackThatProvidesABucket(app, "Stack1", env=prod)
# stack2 will take a property "bucket"
stack2 = StackThatExpectsABucket(app, "Stack2", bucket=stack1.bucket, env=prod)
- Java
-
// Helper method to build an environment
static Environment makeEnv(String account, String region) {
return Environment.builder().account(account).region(region)
.build();
}
App app = new App();
Environment prod = makeEnv("123456789012", "us-east-1");
StackThatProvidesABucket stack1 = new StackThatProvidesABucket(app, "Stack1",
StackProps.builder().env(prod).build());
// stack2 will take an argument "bucket"
StackThatExpectsABucket stack2 = new StackThatExpectsABucket(app, "Stack,",
StackProps.builder().env(prod).build(), stack1.bucket);
- C#
-
Amazon.CDK.Environment makeEnv(string account, string region)
{
return new Amazon.CDK.Environment { Account = account, Region = region };
}
var prod = makeEnv(account: "123456789012", region: "us-east-1");
var stack1 = new StackThatProvidesABucket(app, "Stack1", new StackProps { Env = prod });
// stack2 will take a property "bucket"
var stack2 = new StackThatExpectsABucket(app, "Stack2", new StackProps { Env = prod,
bucket = stack1.Bucket});
If the AWS CDK determines that the resource is in the same account and Region, but in a
different stack, it automatically synthesizes AWS CloudFormation exports in the producing stack
and an Fn::ImportValue
in the consuming stack to transfer that information from one stack to the other.
Resolving dependency deadlocks
Referencing a resource from one stack in a different stack creates a dependency between
the two stacks. This makes sure that they're deployed in the right order. After the stacks
are deployed, this dependency is concrete. After that, removing the use of the shared
resource from the consuming stack can cause an unexpected deployment failure. This happens
if there is another dependency between the two stacks that force them to be deployed in the
same order. It can also happen without a dependency if the producing stack is simply chosen
by the CDK Toolkit to be deployed first. The AWS CloudFormation export is removed from the producing
stack because it's no longer needed, but the exported resource is still being used in the
consuming stack because its update is not yet deployed. Therefore, deploying the producer
stack fails.
To break this deadlock, remove the use of the shared resource from the consuming stack.
(This removes the automatic export from the producing stack.) Next, manually add the same
export to the producing stack using exactly the same logical ID as the automatically
generated export. Remove the use of the shared resource in the consuming stack and deploy
both stacks. Then, remove the manual export (and the shared resource if it's no longer
needed) and deploy both stacks again. The stack's exportValue()
method is a convenient way to create the manual export for
this purpose. (See the example in the linked method reference.)
Referencing resources in your AWS account
Suppose you want to use a resource already available in your AWS account in your AWS CDK
app. This might be a resource that was defined through the console, an AWS SDK, directly
with AWS CloudFormation, or in a different AWS CDK application. You can turn the resource's ARN (or another
identifying attribute, or group of attributes) into a proxy object. The proxy object serves as
a reference to the resource by calling a static factory method on the resource's class.
When you create such a proxy, the external resource does
not become a part of your AWS CDK app. Therefore, changes you make to the proxy in
your AWS CDK app do not affect the deployed resource. The proxy can, however, be passed to any
AWS CDK method that requires a resource of that type.
The following example shows how to reference a bucket based on an existing bucket with the
ARN arn:aws:s3:::my-bucket-name, and an Amazon Virtual Private Cloud based on an
existing VPC having a specific ID.
- TypeScript
-
// Construct a proxy for a bucket by its name (must be same account)
s3.Bucket.fromBucketName(this, 'MyBucket', 'my-bucket-name');
// Construct a proxy for a bucket by its full ARN (can be another account)
s3.Bucket.fromBucketArn(this, 'MyBucket', 'arn:aws:s3:::my-bucket-name');
// Construct a proxy for an existing VPC from its attribute(s)
ec2.Vpc.fromVpcAttributes(this, 'MyVpc', {
vpcId: 'vpc-1234567890abcde',
});
- JavaScript
-
// Construct a proxy for a bucket by its name (must be same account)
s3.Bucket.fromBucketName(this, 'MyBucket', 'my-bucket-name');
// Construct a proxy for a bucket by its full ARN (can be another account)
s3.Bucket.fromBucketArn(this, 'MyBucket', 'arn:aws:s3:::my-bucket-name');
// Construct a proxy for an existing VPC from its attribute(s)
ec2.Vpc.fromVpcAttributes(this, 'MyVpc', {
vpcId: 'vpc-1234567890abcde'
});
- Python
-
# Construct a proxy for a bucket by its name (must be same account)
s3.Bucket.from_bucket_name(self, "MyBucket", "my-bucket-name")
# Construct a proxy for a bucket by its full ARN (can be another account)
s3.Bucket.from_bucket_arn(self, "MyBucket", "arn:aws:s3:::my-bucket-name")
# Construct a proxy for an existing VPC from its attribute(s)
ec2.Vpc.from_vpc_attributes(self, "MyVpc", vpc_id="vpc-1234567890abcdef")
- Java
-
// Construct a proxy for a bucket by its name (must be same account)
Bucket.fromBucketName(this, "MyBucket", "my-bucket-name");
// Construct a proxy for a bucket by its full ARN (can be another account)
Bucket.fromBucketArn(this, "MyBucket",
"arn:aws:s3:::my-bucket-name");
// Construct a proxy for an existing VPC from its attribute(s)
Vpc.fromVpcAttributes(this, "MyVpc", VpcAttributes.builder()
.vpcId("vpc-1234567890abcdef").build());
- C#
-
// Construct a proxy for a bucket by its name (must be same account)
Bucket.FromBucketName(this, "MyBucket", "my-bucket-name");
// Construct a proxy for a bucket by its full ARN (can be another account)
Bucket.FromBucketArn(this, "MyBucket", "arn:aws:s3:::my-bucket-name");
// Construct a proxy for an existing VPC from its attribute(s)
Vpc.FromVpcAttributes(this, "MyVpc", new VpcAttributes
{
VpcId = "vpc-1234567890abcdef"
});
Let's take a closer look at the Vpc.fromLookup()
method. Because the ec2.Vpc
construct
is complex, there are many ways you might want to select the VPC to be used with your
CDK app. To address this, the VPC construct has a fromLookup
static method
(Python: from_lookup
) that lets you look up the desired Amazon VPC by querying your
AWS account at synthesis time.
To use Vpc.fromLookup()
, the system that synthesizes the stack must have
access to the account that owns the Amazon VPC. This is because the CDK Toolkit queries the
account to find the right Amazon VPC at synthesis time.
Furthermore, Vpc.fromLookup()
works only in stacks that are defined with an
explicit account and region
(see Environments). If the AWS CDK tries to look up an Amazon VPC from an environment-agnostic stack, the CDK Toolkit doesn't know which
environment to query to find the VPC.
You must provide Vpc.fromLookup()
attributes sufficient to uniquely identify
a VPC in your AWS account. For example, there can only ever be one default VPC, so it's
sufficient to specify the VPC as the default.
- TypeScript
-
ec2.Vpc.fromLookup(this, 'DefaultVpc', {
isDefault: true
});
- JavaScript
-
ec2.Vpc.fromLookup(this, 'DefaultVpc', {
isDefault: true
});
- Python
-
ec2.Vpc.from_lookup(self, "DefaultVpc", is_default=True)
- Java
-
Vpc.fromLookup(this, "DefaultVpc", VpcLookupOptions.builder()
.isDefault(true).build());
- C#
-
Vpc.FromLookup(this, id = "DefaultVpc", new VpcLookupOptions { IsDefault = true });
You can also use the tags
property to query for VPCs by tag. You can add tags
to the Amazon VPC at the time of its creation by using AWS CloudFormation or the AWS CDK. You can edit tags at any
time after creation by using the AWS Management Console, the AWS CLI, or an AWS SDK. In addition to any
tags you add yourself, the AWS CDK automatically adds the following tags to all VPCs it creates.
-
Name – The name of the VPC.
-
aws-cdk:subnet-name – The name of the subnet.
-
aws-cdk:subnet-type – The type of the subnet: Public,
Private, or Isolated.
- TypeScript
-
ec2.Vpc.fromLookup(this, 'PublicVpc',
{tags: {'aws-cdk:subnet-type': "Public"}});
- JavaScript
-
ec2.Vpc.fromLookup(this, 'PublicVpc',
{tags: {'aws-cdk:subnet-type': "Public"}});
- Python
-
ec2.Vpc.from_lookup(self, "PublicVpc",
tags={"aws-cdk:subnet-type": "Public"})
- Java
-
Vpc.fromLookup(this, "PublicVpc", VpcLookupOptions.builder()
.tags(java.util.Map.of("aws-cdk:subnet-type", "Public")) // Java 9 or later
.build());
- C#
-
Vpc.FromLookup(this, id = "PublicVpc", new VpcLookupOptions
{ Tags = new Dictionary<string, string> { ["aws-cdk:subnet-type"] = "Public" });
Results of Vpc.fromLookup()
are cached in the project's
cdk.context.json
file. (See Runtime context.) Commit this
file to version control so that your app will continue to refer to the same Amazon VPC. This works
even if you later change the attributes of your VPCs in a way that would result in a different
VPC being selected. This is particularly important if you're deploying the stack in an
environment that doesn't have access to the AWS account that defines the VPC, such as CDK Pipelines.
Although you can use an external resource anywhere you'd use a similar resource defined in
your AWS CDK app, you cannot modify it. For example, calling addToResourcePolicy
(Python: add_to_resource_policy
) on an external s3.Bucket
does
nothing.
Physical names
The logical names of resources in AWS CloudFormation are different from the names of resources that are
shown in the AWS Management Console after they're deployed by AWS CloudFormation. The AWS CDK calls these final names
physical names.
For example, AWS CloudFormation might create the Amazon S3 bucket with the logical ID Stack2MyBucket4DD88B4F from the previous example with the physical name
stack2mybucket4dd88b4f-iuv1rbv9z3to.
You can specify a physical name when creating constructs that represent resources by using
the property <resourceType>Name. The following example creates an Amazon S3 bucket with the
physical name my-bucket-name.
- TypeScript
-
const bucket = new s3.Bucket(this, 'MyBucket', {
bucketName: 'my-bucket-name',
});
- JavaScript
-
const bucket = new s3.Bucket(this, 'MyBucket', {
bucketName: 'my-bucket-name'
});
- Python
-
bucket = s3.Bucket(self, "MyBucket", bucket_name="my-bucket-name")
- Java
-
Bucket bucket = Bucket.Builder.create(this, "MyBucket")
.bucketName("my-bucket-name").build();
- C#
-
var bucket = new Bucket(this, "MyBucket", new BucketProps { BucketName = "my-bucket-name" });
Assigning physical names to resources has some disadvantages in AWS CloudFormation. Most importantly,
any changes to deployed resources that require a resource replacement, such as changes to a
resource's properties that are immutable after creation, will fail if a resource has a
physical name assigned. If you end up in that state, the only solution is to delete the AWS CloudFormation
stack, then deploy the AWS CDK app again. See the AWS CloudFormation documentation for
details.
In some cases, such as when creating an AWS CDK app with cross-environment references,
physical names are required for the AWS CDK to function correctly. In those cases, if you don't
want to bother with coming up with a physical name yourself, you can let the AWS CDK name it for
you. To do so, use the special value PhysicalName.GENERATE_IF_NEEDED
, as
follows.
- TypeScript
-
const bucket = new s3.Bucket(this, 'MyBucket', {
bucketName: core.PhysicalName.GENERATE_IF_NEEDED,
});
- JavaScript
-
const bucket = new s3.Bucket(this, 'MyBucket', {
bucketName: core.PhysicalName.GENERATE_IF_NEEDED
});
- Python
-
bucket = s3.Bucket(self, "MyBucket",
bucket_name=core.PhysicalName.GENERATE_IF_NEEDED)
- Java
-
Bucket bucket = Bucket.Builder.create(this, "MyBucket")
.bucketName(PhysicalName.GENERATE_IF_NEEDED).build();
- C#
-
var bucket = new Bucket(this, "MyBucket", new BucketProps
{ BucketName = PhysicalName.GENERATE_IF_NEEDED });
Passing unique identifiers
Whenever possible, you should pass resources by reference, as described in the previous
section. However, there are cases where you have no other choice but to refer to a resource by
one of its attributes. Example use cases include the following:
-
When you are using low-level AWS CloudFormation resources
-
When you need to expose resources to the runtime components of an AWS CDK application,
such as when referring to Lambda functions through environment variables
These identifiers are available as attributes on the resources, such as the
following.
- TypeScript
-
bucket.bucketName
lambdaFunc.functionArn
securityGroup.groupArn
- JavaScript
-
bucket.bucketName
lambdaFunc.functionArn
securityGroup.groupArn
- Python
-
bucket.bucket_name
lambda_func.function_arn
security_group_arn
- Java
-
The Java AWS CDK binding uses getter methods for attributes.
bucket.getBucketName()
lambdaFunc.getFunctionArn()
securityGroup.getGroupArn()
- C#
-
bucket.BucketName
lambdaFunc.FunctionArn
securityGroup.GroupArn
The following example shows how to pass a generated bucket name to an AWS Lambda
function.
- TypeScript
-
const bucket = new s3.Bucket(this, 'Bucket');
new lambda.Function(this, 'MyLambda', {
// ...
environment: {
BUCKET_NAME: bucket.bucketName,
},
});
- JavaScript
-
const bucket = new s3.Bucket(this, 'Bucket');
new lambda.Function(this, 'MyLambda', {
// ...
environment: {
BUCKET_NAME: bucket.bucketName
}
});
- Python
-
bucket = s3.Bucket(self, "Bucket")
lambda.Function(self, "MyLambda", environment=dict(BUCKET_NAME=bucket.bucket_name))
- Java
-
final Bucket bucket = new Bucket(this, "Bucket");
Function.Builder.create(this, "MyLambda")
.environment(java.util.Map.of( // Java 9 or later
"BUCKET_NAME", bucket.getBucketName()))
.build();
- C#
-
var bucket = new Bucket(this, "Bucket");
new Function(this, "MyLambda", new FunctionProps
{
Environment = new Dictionary<string, string>
{
["BUCKET_NAME"] = bucket.BucketName
}
});
Granting permissions
AWS constructs make least-privilege permissions achievable by offering simple,
intent-based APIs to express permission requirements. Many AWS constructs offer grant
methods that you can use to grant an entity (such as an IAM role or user) permission to work
with the resource, without having to manually create IAM permission statements.
The following example creates the permissions to allow a Lambda function's execution role
to read and write objects to a particular Amazon S3 bucket. If the Amazon S3 bucket is encrypted with an
AWS KMS key, this method also grants permissions to the Lambda function's execution role to
decrypt with the key.
- TypeScript
-
if (bucket.grantReadWrite(func).success) {
// ...
}
- JavaScript
-
if ( bucket.grantReadWrite(func).success) {
// ...
}
- Python
-
if bucket.grant_read_write(func).success:
# ...
- Java
-
if (bucket.grantReadWrite(func).getSuccess()) {
// ...
}
- C#
-
if (bucket.GrantReadWrite(func).Success)
{
// ...
}
The grant methods return an iam.Grant
object. Use the success
attribute of the Grant
object to determine whether the grant was effectively
applied (for example, it may not have been applied on external resources). You can also use the assertSuccess
(Python:
assert_success
) method of the Grant
object to enforce that the
grant was successfully applied.
If a specific grant method isn't available for the particular use case, you can use a
generic grant method to define a new grant with a specified list of actions.
The following example shows how to grant a Lambda function access to the Amazon DynamoDB
CreateBackup
action.
- TypeScript
-
table.grant(func, 'dynamodb:CreateBackup');
- JavaScript
-
table.grant(func, 'dynamodb:CreateBackup');
- Python
-
table.grant(func, "dynamodb:CreateBackup")
- Java
-
table.grant(func, "dynamodb:CreateBackup");
- C#
-
table.Grant(func, "dynamodb:CreateBackup");
Many resources, such as Lambda functions, require a role to be assumed when executing code.
A configuration property enables you to specify an iam.IRole
. If no role is
specified, the function automatically creates a role specifically for this use. You can then
use grant methods on the resources to add statements to the role.
The grant methods are built using lower-level APIs for handling with IAM policies. Policies are modeled as
PolicyDocument objects. Add statements directly to roles (or a construct's attached role) using the
addToRolePolicy
method (Python: add_to_role_policy
), or to a resource's policy (such as a
Bucket
policy) using the addToResourcePolicy
(Python: add_to_resource_policy
)
method.
Metrics and alarms
Many resources emit CloudWatch metrics that can be used to set up monitoring dashboards and
alarms. AWS constructs have metric methods that let you access the metrics without looking
up the correct name to use.
The following example shows how to define an alarm when the
ApproximateNumberOfMessagesNotVisible
of an Amazon SQS queue exceeds 100.
- TypeScript
-
import * as cw from '@aws-cdk/aws-cloudwatch';
import * as sqs from '@aws-cdk/aws-sqs';
import { Duration } from '@aws-cdk/core';
const queue = new sqs.Queue(this, 'MyQueue');
const metric = queue.metricApproximateNumberOfMessagesNotVisible({
label: 'Messages Visible (Approx)',
period: Duration.minutes(5),
// ...
});
metric.createAlarm(this, 'TooManyMessagesAlarm', {
comparisonOperator: cw.ComparisonOperator.GREATER_THAN_THRESHOLD,
threshold: 100,
// ...
});
- JavaScript
-
const cw = require('@aws-cdk/aws-cloudwatch');
const sqs = require('@aws-cdk/aws-sqs');
const { Duration } = require('@aws-cdk/core');
const queue = new sqs.Queue(this, 'MyQueue');
const metric = queue.metricApproximateNumberOfMessagesNotVisible({
label: 'Messages Visible (Approx)',
period: Duration.minutes(5)
// ...
});
metric.createAlarm(this, 'TooManyMessagesAlarm', {
comparisonOperator: cw.ComparisonOperator.GREATER_THAN_THRESHOLD,
threshold: 100
// ...
});
- Python
-
import aws_cdk.aws_cloudwatch as cw
import aws_cdk.aws_sqs as sqs
from aws_cdk.core import Duration
queue = sqs.Queue(self, "MyQueue")
metric = queue.metric_approximate_number_of_messages_not_visible(
label="Messages Visible (Approx)",
period=Duration.minutes(5),
# ...
)
metric.create_alarm(self, "TooManyMessagesAlarm",
comparison_operator=cw.ComparisonOperator.GREATER_THAN_THRESHOLD,
threshold=100,
# ...
)
- Java
-
import software.amazon.awscdk.core.Duration;
import software.amazon.awscdk.services.sqs.Queue;
import software.amazon.awscdk.services.cloudwatch.Metric;
import software.amazon.awscdk.services.cloudwatch.MetricOptions;
import software.amazon.awscdk.services.cloudwatch.CreateAlarmOptions;
import software.amazon.awscdk.services.cloudwatch.ComparisonOperator;
Queue queue = new Queue(this, "MyQueue");
Metric metric = queue
.metricApproximateNumberOfMessagesNotVisible(MetricOptions.builder()
.label("Messages Visible (Approx)")
.period(Duration.minutes(5)).build());
metric.createAlarm(this, "TooManyMessagesAlarm", CreateAlarmOptions.builder()
.comparisonOperator(ComparisonOperator.GREATER_THAN_THRESHOLD)
.threshold(100)
// ...
.build());
- C#
-
using cdk = Amazon.CDK;
using cw = Amazon.CDK.AWS.CloudWatch;
using sqs = Amazon.CDK.AWS.SQS;
var queue = new sqs.Queue(this, "MyQueue");
var metric = queue.MetricApproximateNumberOfMessagesNotVisible(new cw.MetricOptions
{
Label = "Messages Visible (Approx)",
Period = cdk.Duration.Minutes(5),
// ...
});
metric.CreateAlarm(this, "TooManyMessagesAlarm", new cw.CreateAlarmOptions
{
ComparisonOperator = cw.ComparisonOperator.GREATER_THAN_THRESHOLD,
Threshold = 100,
// ..
});
If there is no method for a particular metric, you can use the general metric method to
specify the metric name manually.
Metrics can also be added to CloudWatch dashboards. See CloudWatch.
Network traffic
In many cases, you must enable permissions on a network for an application to work, such
as when the compute infrastructure needs to access the persistence layer. Resources that
establish or listen for connections expose methods that enable traffic flows, including
setting security group rules or network ACLs.
IConnectable resources have a connections
property that is the
gateway to network traffic rules configuration.
You enable data to flow on a given network path by using allow
methods. The
following example enables HTTPS connections to the web and incoming connections from the Amazon EC2
Auto Scaling group fleet2
.
- TypeScript
-
import * as asg from '@aws-cdk/aws-autoscaling';
import * as ec2 from '@aws-cdk/aws-ec2';
const fleet1: asg.AutoScalingGroup = asg.AutoScalingGroup(/*...*/);
// Allow surfing the (secure) web
fleet1.connections.allowTo(new ec2.Peer.anyIpv4(), new ec2.Port({ fromPort: 443, toPort: 443 }));
const fleet2: asg.AutoScalingGroup = asg.AutoScalingGroup(/*...*/);
fleet1.connections.allowFrom(fleet2, ec2.Port.AllTraffic());
- JavaScript
-
const asg = require('@aws-cdk/aws-autoscaling');
const ec2 = require('@aws-cdk/aws-ec2');
const fleet1 = asg.AutoScalingGroup();
// Allow surfing the (secure) web
fleet1.connections.allowTo(new ec2.Peer.anyIpv4(), new ec2.Port({ fromPort: 443, toPort: 443 }));
const fleet2 = asg.AutoScalingGroup();
fleet1.connections.allowFrom(fleet2, ec2.Port.AllTraffic());
- Python
-
import aws_cdk.aws_autoscaling as asg
import aws_cdk.aws_ec2 as ec2
fleet1 = asg.AutoScalingGroup( ... )
# Allow surfing the (secure) web
fleet1.connections.allow_to(ec2.Peer.any_ipv4(),
ec2.Port(PortProps(from_port=443, to_port=443)))
fleet2 = asg.AutoScalingGroup( ... )
fleet1.connections.allow_from(fleet2, ec2.Port.all_traffic())
- Java
-
import software.amazon.awscdk.services.autoscaling.AutoScalingGroup;
import software.amazon.awscdk.services.ec2.Peer;
import software.amazon.awscdk.services.ec2.Port;
AutoScalingGroup fleet1 = AutoScalingGroup.Builder.create(this, "MyFleet")
/* ... */.build();
// Allow surfing the (secure) Web
fleet1.getConnections().allowTo(Peer.anyIpv4(),
Port.Builder.create().fromPort(443).toPort(443).build());
AutoScalingGroup fleet2 = AutoScalingGroup.Builder.create(this, "MyFleet2")
/* ... */.build();
fleet1.getConnections().allowFrom(fleet2, Port.allTraffic());
- C#
-
using cdk = Amazon.CDK;
using asg = Amazon.CDK.AWS.AutoScaling;
using ec2 = Amazon.CDK.AWS.EC2;
// Allow surfing the (secure) Web
var fleet1 = new asg.AutoScalingGroup(this, "MyFleet", new asg.AutoScalingGroupProps { /* ... */ });
fleet1.Connections.AllowTo(ec2.Peer.AnyIpv4(), new ec2.Port(new ec2.PortProps
{ FromPort = 443, ToPort = 443 });
var fleet2 = new asg.AutoScalingGroup(this, "MyFleet2", new asg.AutoScalingGroupProps { /* ... */ });
fleet1.Connections.AllowFrom(fleet2, ec2.Port.AllTraffic());
Certain resources have default ports associated with them. Examples include the listener
of a load balancer on the public port, and the ports on which the database engine accepts
connections for instances of an Amazon RDS database. In such cases, you can enforce tight network
control without having to manually specify the port. To do so, use the
allowDefaultPortFrom
and allowToDefaultPort
methods (Python:
allow_default_port_from
, allow_to_default_port
).
The following example shows how to enable connections from any IPV4 address, and a
connection from an Auto Scaling group to access a database.
- TypeScript
-
listener.connections.allowDefaultPortFromAnyIpv4('Allow public access');
fleet.connections.allowToDefaultPort(rdsDatabase, 'Fleet can access database');
- JavaScript
-
listener.connections.allowDefaultPortFromAnyIpv4('Allow public access');
fleet.connections.allowToDefaultPort(rdsDatabase, 'Fleet can access database');
- Python
-
listener.connections.allow_default_port_from_any_ipv4("Allow public access")
fleet.connections.allow_to_default_port(rds_database, "Fleet can access database")
- Java
-
listener.getConnections().allowDefaultPortFromAnyIpv4("Allow public access");
fleet.getConnections().AllowToDefaultPort(rdsDatabase, "Fleet can access database");
- C#
-
listener.Connections.AllowDefaultPortFromAnyIpv4("Allow public access");
fleet.Connections.AllowToDefaultPort(rdsDatabase, "Fleet can access database");
Event handling
Some resources can act as event sources. Use the addEventNotification
method
(Python: add_event_notification
) to register an event target to a particular
event type emitted by the resource. In addition to this, addXxxNotification
methods offer a simple way to register a handler for common event types.
The following example shows how to trigger a Lambda function when an object is added to an
Amazon S3 bucket.
- TypeScript
-
import * as s3nots from '@aws-cdk/aws-s3-notifications';
const handler = new lambda.Function(this, 'Handler', { /*…*/ });
const bucket = new s3.Bucket(this, 'Bucket');
bucket.addObjectCreatedNotification(new s3nots.LambdaDestination(handler));
- JavaScript
-
const s3nots = require('@aws-cdk/aws-s3-notifications');
const handler = new lambda.Function(this, 'Handler', { /*…*/ });
const bucket = new s3.Bucket(this, 'Bucket');
bucket.addObjectCreatedNotification(new s3nots.LambdaDestination(handler));
- Python
-
import aws_cdk.aws_s3_notifications as s3_nots
handler = lambda_.Function(self, "Handler", ...)
bucket = s3.Bucket(self, "Bucket")
bucket.add_object_created_notification(s3_nots.LambdaDestination(handler))
- Java
-
import software.amazon.awscdk.services.s3.Bucket;
import software.amazon.awscdk.services.lambda.Function;
import software.amazon.awscdk.services.s3.notifications.LambdaDestination;
Function handler = Function.Builder.create(this, "Handler")/* ... */.build();
Bucket bucket = new Bucket(this, "Bucket");
bucket.addObjectCreatedNotification(new LambdaDestination(handler));
- C#
-
using lambda = Amazon.CDK.AWS.Lambda;
using s3 = Amazon.CDK.AWS.S3;
using s3Nots = Amazon.CDK.AWS.S3.Notifications;
var handler = new lambda.Function(this, "Handler", new lambda.FunctionProps { .. });
var bucket = new s3.Bucket(this, "Bucket");
bucket.AddObjectCreatedNotification(new s3Nots.LambdaDestination(handler));
Removal policies
Resources that maintain persistent data, such as databases, Amazon S3 buckets, and Amazon ECR
registries, have a removal policy. The removal policy indicates whether
to delete persistent objects when the AWS CDK stack that contains them is destroyed. The values
specifying the removal policy are available through the RemovalPolicy
enumeration
in the AWS CDK core
module.
Resources besides those that store data persistently might also have a
removalPolicy
that is used for a different purpose. For example, a Lambda
function version uses a removalPolicy
attribute to determine whether a given
version is retained when a new version is deployed. These have different meanings and
defaults compared to the removal policy on an Amazon S3 bucket or DynamoDB table.
Value |
meaning |
RemovalPolicy.RETAIN |
Keep the contents of the resource when destroying the stack (default). The resource is
orphaned from the stack and must be deleted manually. If you attempt to re-deploy the
stack while the resource still exists, you will receive an error message due to a name
conflict. |
RemovalPolicy.DESTROY |
The resource will be destroyed along with the stack. |
AWS CloudFormation does not remove Amazon S3 buckets that contain files even if their removal policy is set
to DESTROY
. Attempting to do so is an AWS CloudFormation error. To have the AWS CDK delete all
files from the bucket before destroying it, set the bucket's autoDeleteObjects
property to true
.
Following is an example of creating an Amazon S3 bucket with RemovalPolicy
of
DESTROY
and autoDeleteOjbects
set to true
.
- TypeScript
-
import * as cdk from '@aws-cdk/core';
import * as s3 from '@aws-cdk/aws-s3';
export class CdkTestStack extends cdk.Stack {
constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
super(scope, id, props);
const bucket = new s3.Bucket(this, 'Bucket', {
removalPolicy: cdk.RemovalPolicy.DESTROY,
autoDeleteObjects: true
});
}
}
- JavaScript
-
const cdk = require('@aws-cdk/core');
const s3 = require('@aws-cdk/aws-s3');
class CdkTestStack extends cdk.Stack {
constructor(scope, id, props) {
super(scope, id, props);
const bucket = new s3.Bucket(this, 'Bucket', {
removalPolicy: cdk.RemovalPolicy.DESTROY,
autoDeleteObjects: true
});
}
}
module.exports = { CdkTestStack }
- Python
-
import aws_cdk.core as cdk
import aws_cdk.aws_s3 as s3
class CdkTestStack(cdk.stack):
def __init__(self, scope: cdk.Construct, id: str, **kwargs):
super().__init__(scope, id, **kwargs)
bucket = s3.Bucket(self, "Bucket",
removal_policy=cdk.RemovalPolicy.DESTROY,
auto_delete_objects=True)
- Java
-
software.amazon.awscdk.core.*;
import software.amazon.awscdk.services.s3.*;
public class CdkTestStack extends Stack {
public CdkTestStack(final Construct scope, final String id) {
this(scope, id, null);
}
public CdkTestStack(final Construct scope, final String id, final StackProps props) {
super(scope, id, props);
Bucket.Builder.create(this, "Bucket")
.removalPolicy(RemovalPolicy.DESTROY)
.autoDeleteObjects(true).build();
}
}
- C#
-
using Amazon.CDK;
using Amazon.CDK.AWS.S3;
public CdkTestStack(Construct scope, string id, IStackProps props) : base(scope, id, props)
{
new Bucket(this, "Bucket", new BucketProps {
RemovalPolicy = RemovalPolicy.DESTROY,
AutoDeleteObjects = true
});
}
You can also apply a removal policy directly to the underlying AWS CloudFormation resource via the
applyRemovalPolicy()
method. This method is available on some stateful
resources that do not have a removalPolicy
property in their L2 resource's props.
Examples include the following:
-
AWS CloudFormation stacks
-
Amazon Cognito user pools
-
Amazon DocumentDB database instances
-
Amazon EC2 volumes
-
Amazon OpenSearch Service domains
-
Amazon FSx file systems
-
Amazon SQS queues
- TypeScript
-
const resource = bucket.node.findChild('Resource') as cdk.CfnResource;
resource.applyRemovalPolicy(cdk.RemovalPolicy.DESTROY);
- JavaScript
-
const resource = bucket.node.findChild('Resource');
resource.applyRemovalPolicy(cdk.RemovalPolicy.DESTROY);
- Python
-
resource = bucket.node.find_child('Resource')
resource.apply_removal_policy(cdk.RemovalPolicy.DESTROY);
- Java
-
CfnResource resource = (CfnResource)bucket.node.findChild("Resource");
resource.applyRemovalPolicy(cdk.RemovalPolicy.DESTROY);
- C#
-
var resource = (CfnResource)bucket.node.findChild('Resource');
resource.ApplyRemovalPolicy(cdk.RemovalPolicy.DESTROY);
The AWS CDK's RemovalPolicy
translates to AWS CloudFormation's
DeletionPolicy
. However, the default in AWS CDK is to retain the data, which is
the opposite of the AWS CloudFormation default.