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Event Grid triggered Function App on Locally

This example shows how to deploy an Event Grid triggered Function App - which records every resource deployment in your subscription into PostgreSQL - to Locally Build.

Requirements

• Locally Build.
• Either HashiCorp Terraform or OpenTofu.
• Either Docker or Podman (recommended).
• Node.js 20+, to install the function's dependencies.
• The Locally Plugin for Microsoft.DBforPostgreSQL installed (locally plugin install --name Microsoft.DBforPostgreSQL).
• The Locally Plugin for Microsoft.EventGrid installed (locally plugin install --name Microsoft.EventGrid).
• The Locally Plugin for Microsoft.Storage installed (locally plugin install --name Microsoft.Storage).
• The Locally Plugin for Microsoft.Web installed (locally plugin install --name Microsoft.Web).

Running the example

First up, we need to ensure Locally is running, which can be launched via:

locally build

The Function App is deployed from a zip that Terraform builds from function/, so we first install its dependencies:

cd function
npm install
cd ..

With Locally running, in another terminal we can initialise Terraform, which both downloads the providers we need and then configures the modules for use:

cd environments/locally
terraform init

Note

It's possible to use OpenTofu here by substituting terraform for tofu.

With Terraform initialised, we can then provision the example by running:

locally run terraform apply

One apply creates the resource group, storage account, plan and Function App, pushes the code into the app, creates the subscription-scoped Event Grid system topic, and subscribes the function to it.

Triggering the function

The system topic watches the whole subscription, so deploying any resource fires the function. Note that it's writes to resources that raise the event, not the resource group that contains them - so deploy a resource, for example a storage account:

locally run az group create -n trigger-rg -l berlin
locally run az storage account create -n triggersa$RANDOM -g trigger-rg -l berlin --sku Standard_LRS

Delivery is picked up on a poll, so give it a few seconds, then read back everything the function has been handed from the received_url output:

curl "$(locally run terraform output -raw received_url)"

Tearing it down

cd environments/locally
locally run terraform destroy

The trigger-rg resource group you created above to fire an event isn't part of this configuration, so remove it separately:

locally run az group delete -n trigger-rg --yes