Tenant-Specific Data Isolation in Azure SQL Databases

Question

Pulumi · Accepted Answer

In a multi-tenant architecture, where a single instance of software may serve multiple tenant customers, data isolation is a critical aspect. In Azure SQL Databases, tenant-specific data isolation can be achieved by having separate databases for each tenant, or by implementing row-level security within a single database.

For tenant-specific data isolation, we'll use Pulumi to programmatically create managed SQL databases within an Azure SQL Server instance. Each managed database will act as an isolated container for a tenant's data.

Pulumi provides an infrastructure as code tool to define cloud resources using familiar programming languages. In this case, we'll use Python to define our resources.

Here's a high-level outline of steps we'll take with the Pulumi Python program to achieve tenant-specific data isolation in Azure SQL Databases:

1. **Setup**: Import all necessary Pulumi modules for interacting with Azure
2. **SQL Server Creation**: Define an Azure SQL Server resource that will host tenant-specific databases.
3. **Managed Databases Creation**: Define managed database resources within the SQL server for each tenant, ensuring data isolation.
4. **Configuration and Outputs**: Apply any necessary configurations and export outputs such as the connection strings for each tenant's database.

Let's write a Pulumi Python program that accomplishes these steps:

```python
import pulumi
import pulumi_azure_native as azure_native

# Start by defining the configuration for our SQL server.

# Create an Azure Resource Group to hold all related resources
resource_group = azure_native.resources.ResourceGroup('tenantResourceGroup')

# Create an Azure SQL Server to host our managed databases
sql_server = azure_native.sql.Server('tenantSqlServer',
    resource_group_name=resource_group.name,
    location=resource_group.location,
    administrator_login='sqladmin',                         # Use an appropriate username
    administrator_login_password='SecurePassword123!',      # Replace with a secure password
    version='12.0')                                         # Specify the SQL Server version

# Define a list of tenants. In a real-world scenario, this could be from a database or API
tenants = ['TenantA', 'TenantB', 'TenantC']

# Loop over tenants list to create a separate Managed Database for each tenant
tenant_databases = {}
for tenant in tenants:
    # Each tenant gets their own managed database for isolation
    tenant_databases[tenant] = azure_native.sql.ManagedDatabase(
        f'dbFor{tenant}',
        resource_group_name=resource_group.name,
        managed_instance_name=sql_server.name,             # Associate with the SQL Server created above
        location=resource_group.location,
        database_name=tenant)                              # Name the database after the tenant

# Output connection strings for each tenant database
tenant_connection_strings = {
    tenant: pulumi.Output.all(resource_group.name, sql_server.name, tenant_databases[tenant].name).apply(
        lambda args: f"Server=tcp:{args[1]}.database.windows.net;Database={args[2]};User ID=sqladmin;Password=SecurePassword123!;Encrypt=true;Connection Timeout=30;")
    for tenant in tenants
}

# Export the SQL Server name and tenant connection strings
pulumi.export('sqlServerName', sql_server.name)
pulumi.export('tenantConnectionStrings', tenant_connection_strings)
```

In the above program, we start by importing the necessary Pulumi package `pulumi_azure_native` to manage Azure resources.

- We then create a new resource group to house all resources pertaining to tenant isolation (`ResourceGroup`).
- Next, we create an Azure SQL Server (`Server`) which will contain all the managed databases. Notice that we provide an administrator login and password—these credentials should be secured and managed appropriately in a real-world scenario. 
- We define a list of tenants and loop through them, creating an isolated `ManagedDatabase` for each within the SQL server.
- Finally, we export the server name and a dictionary of tenant-specific SQL connection strings. The connection strings can be used by applications to connect to their respective databases securely.

This program achieves the goal of tenant-specific data isolation within Azure SQL Databases via Pulumi using Python. If you're new to Pulumi, you'll want to set up the Pulumi CLI, authenticate with Azure, and then run `pulumi up` to deploy these resources. To remove the resources, run `pulumi destroy`. Make sure to never expose sensitive information like SQL server admin passwords, and instead use Pulumi's secret management or environment variables.