Create an Azure Function with the Azure Cosmos DB Trigger to listen to the Change Feed
In this tutorial we will set up an Azure Cosmos DB and Azure Function App using Terraform and from there we will create and deploy an Azure Function written in Node.js that listens to the Azure Cosmos DB change feed for changes to the database
Creating an Azure Function with the Azure Cosmos DB Trigger
Terraform Configuration File
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terraform {
required_providers {
azurerm = {
source = "hashicorp/azurerm"
version = "=3.110.0"
}
}
}
provider "azurerm" {
features {
resource_group {
prevent_deletion_if_contains_resources = false
}
}
}
resource "azurerm_resource_group" "rg" {
name = "ces-tf-terraform-rg"
location = "West US 2"
tags = {
environment = "dev"
source = "terraform"
owner = "cloudengineerskills"
}
}
resource "azurerm_storage_account" "func_storage" {
name = "cloudengineerskillstfsa"
resource_group_name = azurerm_resource_group.rg.name
location = azurerm_resource_group.rg.location
account_tier = "Standard"
account_replication_type = "LRS"
tags = {
environment = "dev"
source = "terraform"
owner = "cloudengineerskills"
}
}
resource "azurerm_service_plan" "func_consumption_plan" {
name = "cloudengineerskillstfconsumptionplan"
resource_group_name = azurerm_resource_group.rg.name
location = azurerm_resource_group.rg.location
os_type = "Linux"
sku_name = "Y1"
tags = {
environment = "dev"
source = "terraform"
owner = "cloudengineerskills"
}
}
resource "azurerm_log_analytics_workspace" "logs" {
name = "workspace-test"
location = azurerm_resource_group.rg.location
resource_group_name = azurerm_resource_group.rg.name
sku = "PerGB2018"
retention_in_days = 30
tags = {
environment = "dev"
source = "terraform"
owner = "cloudengineerskills"
}
}
resource "azurerm_application_insights" "insights" {
name = "tf-test-appinsights"
location = azurerm_resource_group.rg.location
resource_group_name = azurerm_resource_group.rg.name
workspace_id = azurerm_log_analytics_workspace.logs.id
application_type = "Node.JS"
tags = {
environment = "dev"
source = "terraform"
owner = "cloudengineerskills"
}
}
resource "azurerm_linux_function_app" "func_app" {
name = "cloudengineerskillstffuncapp"
resource_group_name = azurerm_resource_group.rg.name
location = azurerm_resource_group.rg.location
storage_account_name = azurerm_storage_account.func_storage.name
storage_account_access_key = azurerm_storage_account.func_storage.primary_access_key
service_plan_id = azurerm_service_plan.func_consumption_plan.id
site_config {
application_stack {
node_version = 20
}
application_insights_connection_string = azurerm_application_insights.insights.connection_string
application_insights_key = azurerm_application_insights.insights.instrumentation_key
}
app_settings = {
"COSMOSDB_CONNECTION_STRING" = azurerm_cosmosdb_account.db_account.primary_sql_connection_string
}
tags = {
environment = "dev"
source = "terraform"
owner = "cloudengineerskills"
}
}
resource "azurerm_cosmosdb_account" "db_account" {
name = "cloudengineerskills-tf-dbacc"
location = azurerm_resource_group.rg.location
resource_group_name = azurerm_resource_group.rg.name
offer_type = "Standard"
kind = "GlobalDocumentDB"
geo_location {
location = azurerm_resource_group.rg.location
failover_priority = 0
}
consistency_policy {
consistency_level = "Session"
}
capabilities {
name = "EnableServerless"
}
free_tier_enabled = true
depends_on = [
azurerm_resource_group.rg
]
tags = {
environment = "dev"
source = "terraform"
owner = "cloudengineerskills"
}
}
resource "azurerm_cosmosdb_sql_database" "db" {
name = "my-database"
resource_group_name = azurerm_resource_group.rg.name
account_name = azurerm_cosmosdb_account.db_account.name
}
resource "azurerm_cosmosdb_sql_container" "db_container" {
name = "my-container"
resource_group_name = azurerm_resource_group.rg.name
account_name = azurerm_cosmosdb_account.db_account.name
database_name = azurerm_cosmosdb_sql_database.db.name
partition_key_paths = ["/id"]
partition_key_version = 1
indexing_policy {
indexing_mode = "consistent"
included_path {
path = "/*"
}
included_path {
path = "/included/?"
}
excluded_path {
path = "/excluded/?"
}
}
}
Provision the Azure Resources
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terraform init
terraform apply
Create and Deploy the Azure Function
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func init
func new
Trigger Function Code
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const { app } = require("@azure/functions");
app.cosmosDB("cosmosDBTrigger", {
connection: "COSMOSDB_CONNECTION_STRING",
databaseName: "my-database",
containerName: "my-container",
createLeaseContainerIfNotExists: true,
handler: (documents, context) => {
context.log(`Cosmos DB function processed ${documents.length} documents`);
},
});
Deploy the Azure Function
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func azure functionapp publish cloudengineerskillstffuncapp
Using the Azure Portal to Monitor Azure Function Logs after Cosmos DB
- Go into the Azure Portal and in the Resource Groups section you should see the resource group provisioned by Azure
- If you select the resource group, go into the Azure Function App resource
- Select your cosmosDBTrigger function, go into Logs and wait for Application Insights to connect
- Back in your resource group, go into the Azure Cosmos DB account resource
- Have a look in the Data Explorer and you should see the Azure Cosmos DB database resource
- Within the Azure Cosmos DB database resource you should see the Azure Cosmos DB container resource
- Using the Data Explorer create a new item and save it, check the logs for the cosmosDBTrigger function and verify a new log has been created
- Try creating, updating, and deleting more items and review the function logs. Note that the change feed monitors for creates and updates but does not track deletions.
Sample items you can add to your database container
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{
"id": "1",
"title": "Complete Project Report",
"description": "Compile all project data and create a comprehensive report covering all phases of the project, including milestones, deliverables, and outcomes.",
"status": "In Progress",
"priority": "High",
"due_date": "2024-09-15"
}
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{
"id": "2",
"title": "Design Marketing Campaign",
"description": "Develop a creative marketing campaign for the upcoming product launch, focusing on social media and email marketing strategies.",
"status": "Not Started",
"priority": "Medium",
"due_date": "2024-10-01"
}
Cleaning up the resources
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terraform destroy
Further Reading
- https://learn.microsoft.com/en-us/javascript/api/@azure/functions/cosmosdbv4functionoptions?view=azure-node-latest
This post is licensed under
CC BY 4.0
by the author.