Components

Pulumi allows users to define their own logical aggregations of resources called components and so does Besom. The API is a bit different in comparison to other Pulumi SDKs. User is expected to define a case class that will contain all the Output properties one wants to expose from the internals of the component.

The case class has to:

1. extend besom.ComponentResource trait
2. have a (using ComponentBase) clause after it's primary constructor
3. have a derives RegistersOutputs at the end of it's class declaration

Next step is to declare a function that will use the component constructor function to compose all the resources together. Every component expects:

• a unique resource name as the first argument (usually it's an information that the end user has to provide)
• a resource type which is a string formatted specifically to fit Pulumi's model
• and, as the second argument list of component function, the block of code that defines all the resources that should belong to the component.

Here's a small example using the S3 bucket resource again:

import besom.*
import besom.api.aws
import java.time.OffsetDateTime

case class ZooVisit(
  catPicsUrl: Output[String], 
  parrotPicsUrl: Output[String]
)(using ComponentBase) 
  extends ComponentResource 
  derives RegistersOutputs
object ZooVisit:
  def apply(date: OffsetDateTime)(using Context): Output[ZooVisit] = 
    component(s"zoo-visit-at-$date", "user:component:ZooVisit") { 
      val cats = aws.s3.Bucket(s"cats-$date")
      val parrots = aws.s3.Bucket(s"parrot-$date")
      ZooVisit(cats.websiteEndpoint, parrots.websiteEndpoint)
    }

@main def main = Pulumi.run {
  val visit = ZooVisit(OffsetDateTime.now())

  Stack.exports(
    cats    = visit.map(_.catPicsUrl),
    parrots = visit.map(_.parrotPicsUrl)
  )
}