Get outputs and parameters from remote CDK stacks


License
Apache-2.0
Install
pip install cdk-remote-stack==0.1.189

Documentation

awscdk-jsii-template NPM version PyPI version Build

cdk-remote-stack

Get outputs from cross-regional AWS CDK stacks

Why

AWS CDK cross-regional cross-stack reference is not easy with the native AWS CDK construct library.

cdk-remote-stack aims to simplify the cross-regional cross-stack reference to help you easily build cross-regional multi-stack AWS CDK apps.

This construct library provides two major constructs:

  • RemoteOutputs - cross regional stack outputs reference.
  • RemoteParameters - cross regional/account SSM parameters reference.

RemoteOutputs

RemoteOutputs is ideal for one stack referencing the outputs from another across different AWS regions.

Let's say we have two cross-regional CDK stacks in the same cdk app:

  1. stackJP - cdk stack in JP to create a SNS topic
  2. stackUS - cdk stack in US to get the Outputs from stackJP and print out the SNS TopicName from stackJP Outputs.
import { RemoteOutputs } from 'cdk-remote-stack';
import * as cdk from '@aws-cdk/core';

const app = new cdk.App();

const envJP = {
  region: 'ap-northeast-1',
  account: process.env.CDK_DEFAULT_ACCOUNT,
};

const envUS = {
  region: 'us-west-2',
  account: process.env.CDK_DEFAULT_ACCOUNT,
};

// first stack in JP
const stackJP = new cdk.Stack(app, 'demo-stack-jp', { env: envJP })

new cdk.CfnOutput(stackJP, 'TopicName', { value: 'foo' })

// second stack in US
const stackUS = new cdk.Stack(app, 'demo-stack-us', { env: envUS })

// ensure the dependency
stackUS.addDependency(stackJP)

// get the stackJP stack outputs from stackUS
const outputs = new RemoteOutputs(stackUS, 'Outputs', { stack: stackJP })

const remoteOutputValue = outputs.get('TopicName')

// the value should be exactly the same with the output value of `TopicName`
new cdk.CfnOutput(stackUS, 'RemoteTopicName', { value: remoteOutputValue })

At this moment, RemoteOutputs only supports cross-regional reference in a single AWS account.

always get the latest stack output

By default, the RemoteOutputs construct will always try to get the latest output from the source stack. You may opt out by setting alwaysUpdate to false to turn this feature off.

For example:

const outputs = new RemoteOutputs(stackUS, 'Outputs', { 
  stack: stackJP,
  alwaysUpdate: false,
})

RemoteParameters

AWS SSM Parameter Store is great to store and persist parameters and allow stacks from other regons/accounts to reference. Let's dive into the two major scenarios below:

#1 - Stacks from single account and different regions

In this sample, we create two stacks from JP(ap-northeast-1) and US(us-west-2). The JP stack will produce and update parameters in its parameter store, while the US stack will consume the parameters across differnt regions with the RemoteParameters construct.

    const envJP = { region: 'ap-northeast-1', account: '111111111111' };
    const envUS = { region: 'us-west-2', account: '111111111111' };

    // first stack in JP
    const producerStackName = 'demo-stack-jp';
    const stackJP = new cdk.Stack(app, producerStackName, { env: envJP });
    const parameterPath = `/${envJP.account}/${envJP.region}/${producerStackName}`

    new ssm.StringParameter(stackJP, 'foo1', {
      parameterName: `${parameterPath}/foo1`,
      stringValue: 'bar1',
    });
    new ssm.StringParameter(stackJP, 'foo2', {
      parameterName: `${parameterPath}/foo2`,
      stringValue: 'bar2',
    });
    new ssm.StringParameter(stackJP, 'foo3', {
      parameterName: `${parameterPath}/foo3`,
      stringValue: 'bar3',
    });

    // second stack in US
    const stackUS = new cdk.Stack(app, 'demo-stack-us', { env: envUS });

    // ensure the dependency
    stackUS.addDependency(stackJP);

    // get remote parameters by path from SSM parameter store
    const parameters = new RemoteParameters(stackUS, 'Parameters', {
      path: parameterPath,
      region: stackJP.region,
    })

    const foo1 = parameters.get(`${parameterPath}/foo1`);
    const foo2 = parameters.get(`${parameterPath}/foo2`);
    const foo3 = parameters.get(`${parameterPath}/foo3`);

    new cdk.CfnOutput(stackUS, 'foo1Output', { value: foo1 });
    new cdk.CfnOutput(stackUS, 'foo2Output', { value: foo2 });
    new cdk.CfnOutput(stackUS, 'foo3Output', { value: foo3 });

#2 - Stacks from differnt accounts and different regions

Similar to the case above, now we are running seperate stacks in seperate account/region. We will need to pass a role to the RemoteParameters construct to get all the parameters from remote.

    const envJP = { region: 'ap-northeast-1', account: '111111111111' };
    const envUS = { region: 'us-west-2', account: '222222222222' };

    // first stack in JP
    const producerStackName = 'demo-stack-jp';
    const stackJP = new cdk.Stack(app, producerStackName, { env: envJP });
    const parameterPath = `/${envJP.account}/${envJP.region}/${producerStackName}`

    new ssm.StringParameter(stackJP, 'foo1', {
      parameterName: `${parameterPath}/foo1`,
      stringValue: 'bar1',
    });
    new ssm.StringParameter(stackJP, 'foo2', {
      parameterName: `${parameterPath}/foo2`,
      stringValue: 'bar2',
    });
    new ssm.StringParameter(stackJP, 'foo3', {
      parameterName: `${parameterPath}/foo3`,
      stringValue: 'bar3',
    });

    // allow US account to assume this readonly role to get parameters
    const cdkReadOnlyRole = new iam.Role(stackJP, 'readOnlyRole', {
      assumedBy: new iam.AccountPrincipal(envUS.account),
      roleName: PhysicalName.GENERATE_IF_NEEDED,
      managedPolicies: [ iam.ManagedPolicy.fromAwsManagedPolicyName('AmazonSSMReadOnlyAccess')],
    })

    // second stack in US
    const stackUS = new cdk.Stack(app, 'demo-stack-us', { env: envUS });

    // ensure the dependency
    stackUS.addDependency(stackJP);

    // get remote parameters by path from SSM parameter store
    const parameters = new RemoteParameters(stackUS, 'Parameters', {
      path: parameterPath,
      region: stackJP.region,
      // assume this role for cross-account parameters
      role: iam.Role.fromRoleArn(stackUS, 'readOnlyRole', cdkReadOnlyRole.roleArn),
    })

    const foo1 = parameters.get(`${parameterPath}/foo1`);
    const foo2 = parameters.get(`${parameterPath}/foo2`);
    const foo3 = parameters.get(`${parameterPath}/foo3`);

    new cdk.CfnOutput(stackUS, 'foo1Output', { value: foo1 });
    new cdk.CfnOutput(stackUS, 'foo2Output', { value: foo2 });
    new cdk.CfnOutput(stackUS, 'foo3Output', { value: foo3 });

#3 - dedicated account for a centralized parameter store

The parameters are stored in a centralized account/region and previously provisioned as a state-of-truth configuration store. All other stacks from different account/region are consuming the parameters from remote.

This scenario is pretty much like #2. The difference is that there's a dedicated account for centralized parameter store being shared across all other accounts.

You will need create RemoteParameters for all the consuming stacks like:

// for StackUS
new RemoteParameters(stackUS, 'Parameters', {
  path: parameterPath,
  region: 'eu-central-1'
  // assume this role for cross-account parameters
  role: iam.Role.fromRoleArn(stackUS, 'readOnlyRole', sharedReadOnlyRoleArn),
})

// for StackJP
new RemoteParameters(stackJP, 'Parameters', {
  path: parameterPath,
  region: 'eu-central-1'
  // assume this role for cross-account parameters
  role: iam.Role.fromRoleArn(stackJP, 'readOnlyRole', sharedReadOnlyRoleArn),
})

Tools for multi-account deployment

You will need to install cdk-assume-role-credential-plugin so you can deploy stacks from different accounts. Read this blog post to setup this plugin.

Limitation

  1. At this moment, the RemoteParameters construct only support the String data type from parameter store.
  2. Max number of parameters is 100. Will make it configurable in the future PR when required.