What is constructs?
The 'constructs' npm package provides a framework for defining cloud infrastructure in code by composing and sharing reusable components known as constructs. Constructs can represent low-level resources such as a virtual machine, a database, or a piece of code, as well as higher-level abstractions that are composed of these resources. The package is designed to be used with the AWS Cloud Development Kit (CDK) but is also general enough to be used in other contexts.
What are constructs's main functionalities?
Defining Constructs
This feature allows developers to define their own constructs by extending the Construct class. Constructs can encapsulate any number of child constructs and resources, providing a way to create reusable and composable infrastructure components.
{"const { Construct } = require('constructs');\n\nclass MyConstruct extends Construct {\n constructor(scope, id) {\n super(scope, id);\n // Define resources and other constructs here\n }\n}\n\nconst app = new Construct();\nconst myConstruct = new MyConstruct(app, 'MyConstructId');"}
Composing Constructs
This feature demonstrates how to compose constructs within other constructs, allowing for the creation of complex infrastructure systems by nesting constructs.
{"const { Construct } = require('constructs');\n\nclass MyConstruct extends Construct {\n // ...\n}\n\nclass MyCompositeConstruct extends Construct {\n constructor(scope, id) {\n super(scope, id);\n new MyConstruct(this, 'NestedConstruct');\n }\n}\n\nconst app = new Construct();\nconst myComposite = new MyCompositeConstruct(app, 'MyCompositeConstructId');"}
Synthesizing Constructs
This feature shows how to synthesize a construct, which means to generate a representation of the construct's state, typically for the purpose of deploying infrastructure. The 'synthesize' method is part of the 'Node' class, which provides context and lifecycle methods for constructs.
{"const { Construct, Node } = require('constructs');\n\nclass MyConstruct extends Construct {\n // ...\n}\n\nconst app = new Construct();\nconst myConstruct = new MyConstruct(app, 'MyConstructId');\n\nconst synthesized = Node.of(myConstruct).synthesize();\nconsole.log(synthesized);"}
Other packages similar to constructs
serverless
The 'serverless' package allows for defining serverless applications using a simple and concise configuration file. It is similar to 'constructs' in that it enables infrastructure as code, but it is focused specifically on serverless use cases and provides a different abstraction level and feature set.
pulumi
Pulumi is an infrastructure as code tool that allows developers to define infrastructure using general-purpose programming languages. Similar to 'constructs', Pulumi provides a way to create, deploy, and manage cloud infrastructure, but it does not use the construct paradigm and instead relies on standard programming constructs and classes.
Constructs Programming Model
Define composable configuration models through code
User Manual
Scope Relocation
The path of a scope is used as a seed for all names generated within that scope
such as logical names in the AWS CDK or node.uniqueId
.
There are use cases in which an entire construct subtree (scope) needs to be
"relocated" to a different path. The main use case is in order to allow
refactoring while preserving old names.
Be careful: relocating a scope may result in duplicate names. Use at your own
risk.
To relocate a scope, use the node.relocate(root)
method. This method can only
be called before any children are added to the scope and it will impact the
value of node.path
and node.uniqueId
.
If implementing name generation, make sure to refer to node.path
as the root
of the scope's path instead of node.scopes
.
Let's say we had a scope foo
that was originally under the foo
path and it
has a child called childOfFoo
:
const foo = new Construct(root, 'foo');
const childOfFoo = new Construct(foo, 'childOfFoo');
expect(Node.of(foo).path).toBe('foo');
expect(Node.of(childOfFoo).path).toBe('foo/childOfFoo');
Now, we want to refactor our code and hoist it under a new root, say baz
:
const baz = new Construct(root, 'baz');
const foo = new Construct(baz, 'foo');
const childOfFoo = new Construct(foo, 'childOfFoo');
expect(Node.of(foo).path).toBe('bar/foo');
expect(Node.of(childOfFoo).path).toBe('baz/foo/childOfFoo');
If we relocate foo
to foo
, the original paths are preserved:
const baz = new Construct(root, 'baz');
const foo = new Construct(baz, 'foo');
Node.of(construct).relocate('foo');
const childOfFoo = new Construct(foo, 'childOfFoo');
expect(Node.of(foo).path).toBe('foo');
expect(Node.of(childOfFoo).path).toBe('foo/childOfFoo');
Similarly, the uniqueId
of a construct will be derived from this path.
Contributing
This project has adopted the Amazon Open Source Code of
Conduct.
We welcome community contributions and pull requests. See our contribution
guide for more information on how to report issues, set up a
development environment and submit code.
License
This project is distributed under the Apache License, Version 2.0.