Azure Web App with Azure CosmosDB for MongoDB

This sample demonstrates a Python Flask single-page web application called Vacation Planner hosted on an Azure Web App. The app runs on an Azure App Service Plan and stores activity data in the activities collection of the sampledb MongoDB database on an Azure CosmosDB for MongoDB account.

Architecture

The following diagram illustrates the architecture of the solution:

The web app enables users to plan and manage vacation activities, with all data persisted in a CosmosDB-backed MongoDB collection. The solution is composed of the following Azure resources:

Azure Resource Group: A logical container scoping all resources in this sample.
Azure Virtual Network: Hosts two subnets:
- app-subnet: Dedicated to regional VNet integration with the Function App.
- pe-subnet: Used for hosting Azure Private Endpoints.
Azure Private DNS Zone: Handles DNS resolution for the CosmosDB for MongoDB Private Endpoint within the virtual network.
Azure Private Endpoint: Secures network access to the CosmosDB for MongoDB account via a private IP within the VNet.
Azure NAT Gateway: Provides deterministic outbound connectivity for the Web App. Included for completeness; the sample app does not call any external services.
Azure Network Security Group: Enforces inbound and outbound traffic rules across the virtual network's subnets.
Azure Log Analytics Workspace: Centralizes diagnostic logs and metrics from all resources in the solution.
Azure Cosmos DB for MongoDB: A globally distributed database account optimized for MongoDB workloads, with multi-region failover enabled.
MongoDB Database: The sampledb database that holds all application data.
MongoDB Collection: The activities collection within sampledb, used to store vacation activity records.
Azure App Service Plan: The underlying compute tier that hosts the web application.
Azure Web App: Runs the Python Flask single-page application (Vacation Planner), connected to CosmosDB for MongoDB via VNet integration.
App Service Source Control: (Optional) Configures continuous deployment from a public GitHub repository.

Prerequisites

Azure Subscription
Azure CLI
Python 3.11+
Flask
pymongo
Bicep extension, if you plan to install the sample via Bicep.
Terraform, if you plan to install the sample via Terraform.

Deployment

Set up the Azure emulator using the LocalStack for Azure Docker image. Before starting, ensure you have a valid LOCALSTACK_AUTH_TOKEN to access the Azure emulator. Refer to the Auth Token guide to obtain your Auth Token and set it in the LOCALSTACK_AUTH_TOKEN environment variable. The Azure Docker image is available on the LocalStack Docker Hub. To pull the image, execute:

docker pull localstack/localstack-azure-alpha

Start the LocalStack Azure emulator by running:

# Set the authentication token
export LOCALSTACK_AUTH_TOKEN=<your_auth_token>

# Start the LocalStack Azure emulator
IMAGE_NAME=localstack/localstack-azure-alpha localstack start -d
localstack wait -t 60

# Route all Azure CLI calls to the LocalStack Azure emulator
azlocal start-interception

Deploy the application to LocalStack for Azure using one of these methods:

All deployment methods have been fully tested against Azure and the LocalStack for Azure local emulator.

Note
When you deploy the application to LocalStack for Azure for the first time, the initialization process involves downloading and building Docker images. This is a one-time operation—subsequent deployments will be significantly faster. Depending on your internet connection and system resources, this initial setup may take several minutes.

Test

Retrieve the port published and mapped to port 80 by the Docker container hosting the emulated Web App.
Open a web browser and navigate to http://localhost:<published-port>.
If the deployment was successful, you will see the following user interface for adding and removing activities:

You can use the call-web-app.sh Bash script below to call the web app. The script demonstrates three methods for calling web apps:

Through the LocalStack for Azure emulator: Call the web app via the emulator using its default host name. The emulator acts as a proxy to the web app.
Via localhost and host port mapped to the container's port: Use 127.0.0.1 with the host port mapped to the container's port 80.
Via container IP address: Use the app container's IP address on port 80. This technique is only available when accessing the web app from the Docker host machine.
Via Runtime Gateway: Use the {web_app_name}website.localhost.localstack.cloud:4566 URL to call the web app via the LocalStack runtime gateway.

#!/bin/bash

get_docker_container_name_by_prefix() {
	local app_prefix="$1"
	local container_name

	# Check if Docker is running
	if ! docker info >/dev/null 2>&1; then
		echo "Error: Docker is not running" >&2
		return 1
	fi

	echo "Looking for containers with names starting with [$app_prefix]..." >&2

	# Find the container using grep
	container_name=$(docker ps --format "{{.Names}}" | grep "^${app_prefix}" | head -1)

	if [ -z "$container_name" ]; then
		echo "Error: No running container found with name starting with [$app_prefix]" >&2
		return 1
	fi

	echo "Found matching container [$container_name]" >&2
	echo "$container_name"
}

get_docker_container_ip_address_by_name() {
	local container_name="$1"
	local ip_address

	if [ -z "$container_name" ]; then
		echo "Error: Container name is required" >&2
		return 1
	fi

	# Get IP address
	ip_address=$(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$container_name")

	if [ -z "$ip_address" ]; then
		echo "Error: Container [$container_name] has no IP address assigned" >&2
		return 1
	fi

	echo "$ip_address"
}

get_docker_container_port_mapping() {
	local container_name="$1"
	local container_port="$2"
	local host_port

	if [ -z "$container_name" ] || [ -z "$container_port" ]; then
		echo "Error: Container name and container port are required" >&2
		return 1
	fi

	# Get host port mapping
	host_port=$(docker inspect -f "{{(index (index .NetworkSettings.Ports \"${container_port}/tcp\") 0).HostPort}}" "$container_name")

	if [ -z "$host_port" ]; then
		echo "Error: No host port mapping found for container [$container_name] port [$container_port]" >&2
		return 1
	fi

	echo "$host_port"
}

call_web_app() {
	# Get the web app name
	echo "Getting web app name..."
	web_app_name=$(azlocal webapp list --query '[0].name' --output tsv)

	if [ -n "$web_app_name" ]; then
		echo "Web app [$web_app_name] successfully retrieved."
	else
		echo "Error: No web app found"
		exit 1
	fi

	# Get the resource group name
	echo "Getting resource group name for web app [$web_app_name]..."
	resource_group_name=$(azlocal webapp list --query '[0].resourceGroup' --output tsv)

	if [ -n "$resource_group_name" ]; then
		echo "Resource group [$resource_group_name] successfully retrieved."
	else
		echo "Error: No resource group found for web app [$web_app_name]"
		exit 1
	fi

	# Get the the default host name of the web app
	echo "Getting the default host name of the web app [$web_app_name]..."
	app_host_name=$(azlocal webapp show \
		--name "$web_app_name" \
		--resource-group "$resource_group_name" \
		--query 'defaultHostName' \
		--output tsv)

	if [ -n "$app_host_name" ]; then
		echo "Web app default host name [$app_host_name] successfully retrieved."
	else
		echo "Error: No web app default host name found"
		exit 1
	fi

	# Get the Docker container name
	echo "Finding container name with prefix [ls-$web_app_name]..."
	container_name=$(get_docker_container_name_by_prefix "ls-$web_app_name")

	if [ $? -eq 0 ] && [ -n "$container_name" ]; then
		echo "Container [$container_name] found successfully"
	else
		echo "Failed to get container name"
		exit 1
	fi

	# Get the container IP address
	echo "Getting IP address for container [$container_name]..."
	container_ip=$(get_docker_container_ip_address_by_name "$container_name")

	if [ $? -eq 0 ] && [ -n "$container_ip" ]; then
		echo "IP address [$container_ip] retrieved successfully for container [$container_name]"
	else
		echo "Failed to get container IP address"
		exit 1
	fi

	# Get the mapped host port for web app HTTP trigger (internal port 80)
	echo "Getting the host port mapped to internal port 80 in container [$container_name]..."
	host_port=$(get_docker_container_port_mapping "$container_name" "80")
	
	if [ $? -eq 0 ] && [ -n "$host_port" ]; then
		echo "Mapped host port [$host_port] retrieved successfully for container [$container_name]"
	else
		echo "Failed to get mapped host port for container [$container_name]"
		exit 1
	fi

	# Retrieve LocalStack proxy port
	proxy_port=$(curl http://localhost:4566/_localstack/proxy -s | jq '.proxy_port')

	if [ -n "$proxy_port" ]; then
		# Call the web app via emulator proxy
		echo "Calling web app [$web_app_name] via emulator..."
		curl --proxy "http://localhost:$proxy_port/" -s "http://$app_host_name/" 1> /dev/null
		
		if [ $? == 0 ]; then
			echo "Web app call via emulator proxy port [$proxy_port] succeeded."
		else
			echo "Web app call via emulator proxy port [$proxy_port] failed."
		fi
	else
		echo "Failed to retrieve LocalStack proxy port"
	fi
	
	if [ -n "$container_ip" ]; then
		# Call the web app via the container IP address
		echo "Calling web app [$web_app_name] via container IP address [$container_ip]..."
		curl -s "http://$container_ip/" 1> /dev/null

		if [ $? == 0 ]; then
			echo "Web app call via container IP address [$container_ip] succeeded."
		else
			echo "Web app call via container IP address [$container_ip] failed."
		fi
	else
		echo "Failed to retrieve container IP address"
	fi

	if [ -n "$host_port" ]; then
		# Call the web app via the host port
		echo "Calling web app [$web_app_name] via host port [$host_port]..."
		curl -s "http://127.0.0.1:$host_port/" 1> /dev/null

		if [ $? == 0 ]; then
			echo "Web app call via host port [$host_port] succeeded."
		else
			echo "Web app call via host port [$host_port] failed."
		fi
	else
		echo "Failed to retrieve host port"
	fi

	gateway_port=4566

	if [ -n "$gateway_port" ]; then
		# Call the web app via the runtime gateway
		echo "Calling web app [$web_app_name] via runtime gateway on port [$gateway_port]..."
		curl -s "http://${web_app_name}website.localhost.localstack.cloud:$gateway_port/" 1> /dev/null

		if [ $? == 0 ]; then
			echo "Web app call via runtime gateway on port [$gateway_port] succeeded."
		else
			echo "Web app call via runtime gateway on port [$gateway_port] failed."
		fi
	else
		echo "Failed to retrieve runtime gateway port"
	fi
}

call_web_app

MongoDB Tooling

You can utilize MongoDB Compass to explore and manage your MongoDB databases and collections. Ensure you connect using mongodb://localhost:port connection string, where port corresponds to the port published by the MongoDB container on the host and mapped to the internal MongoDB port 27017.

Alternatively, you can use the MongoDB Shell to interact with and administer your MongoDB instance, as shown in the following table:

~$ mongosh mongodb://localhost:32770
Current Mongosh Log ID: 6914588406320f60899dc29c
Connecting to:          mongodb://localhost:32770/?directConnection=true&serverSelectionTimeoutMS=2000&appName=mongosh+2.5.9
Using MongoDB:          8.0.15
Using Mongosh:          2.5.9

For mongosh info see: https://www.mongodb.com/docs/mongodb-shell/

------
   The server generated these startup warnings when booting
   2025-11-12T09:28:07.726+00:00: Using the XFS filesystem is strongly recommended with the WiredTiger storage engine. See http://dochub.mongodb.org/core/prodnotes-filesystem
   2025-11-12T09:28:07.892+00:00: Access control is not enabled for the database. Read and write access to data and configuration is unrestricted
   2025-11-12T09:28:07.892+00:00: For customers running the current memory allocator, we suggest changing the contents of the following sysfsFile
   2025-11-12T09:28:07.892+00:00: We suggest setting the contents of sysfsFile to 0.
   2025-11-12T09:28:07.892+00:00: vm.max_map_count is too low
   2025-11-12T09:28:07.892+00:00: We suggest setting swappiness to 0 or 1, as swapping can cause performance problems.
------

test> show dbs
admin     100.00 KiB
config    108.00 KiB
local      40.00 KiB
sampledb  180.00 KiB
test> use sampledb
switched to db sampledb
sampledb> show collections
activities
sampledb> db.activities.find().pretty()
[
  {
    _id: '39ab62c2aaa0015ed5309876053e4146',
    username: 'Paolo',
    activity: 'Go to Paris',
    timestamp: '2025-11-12T09:31:43.338268'
  },
  {
    _id: '4fb8f53442d3ebe9167245f9555bac51',
    username: 'Paolo',
    activity: 'Go to Madrid',
    timestamp: '2025-11-12T09:31:50.109456'
  },
  {
    _id: '84646160cb1db21a7083b4c5b6e2d9d0',
    username: 'Paolo',
    activity: 'Go to Rome',
    timestamp: '2025-11-12T09:32:21.781936'
  }
]

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Azure Web App with Azure CosmosDB for MongoDB

Architecture

Prerequisites

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MongoDB Tooling

References

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Azure Web App with Azure CosmosDB for MongoDB

Architecture

Prerequisites

Deployment

Test

MongoDB Tooling

References