Hi! Is it possible to to trigger an update on a resource if a dependency changes? For example:

const basic1 = new BasicResource("basic1", { value: "value1" })
const basic2 = new BasicResource("basic2", { value: "value2" }, { dependsOn: [basic1] })

I'm working on a dynamic resource and I was hoping to be able to run an update on

basic2

when the value of

basic1

changes. The use case I'm trying to address is rebuilding a search engine index if a facet value changes.

Yep you can establish an explicit dependency the way you have it with the use of

dependsOn

. (EDIT: assuming

basic1

changes somehow in order to trigger a change on its dependents.) The other way, if you are interested (and slightly complicated), is to pass some input, that changes based on

basic1

changing, to

basic2

that you can then use in the

diff

function of

basic2

to compare and see if the value has changed. I forget the order of the

DynamicResource

interface functions being called but you might find https://www.pulumi.com/blog/dynamic-providers/ helpful.

Thanks @clever-sunset-76585! It looks like the

check

method is called every time but there doesn't seem to be any reference to the depend. I must be missing something small.

It looks like the 

check

 method is called every time but there doesn’t seem to be any reference to the depend

Yeah

check

is used to validate inputs and return errors if needed to stop execution. You can read more about the various interface functions here, in case you haven’t come across this doc already: https://www.pulumi.com/docs/intro/concepts/programming-model/#check-olds-news

diff

is where you can return an object that indicates whether a replacement/update is required based on some input changing.

t sounds like the simplest solution would be what you suggested and output something like a 

requiresRestart

 property that I could use as an input to the other resource.

While using a boolean might work the first time (going from

false

->

true

, it can only have one of two states. You could use some string output from

basic1

that changes over time based on something else, which in turn could be used within the

diff

function to compare old inputs with new inputs and therefore perform an update/replacement.