Simple Chat

Cosmos Container Throughput Deployer Fix

Cosmos Container Throughput Deployer Fix

Fixed in version: 0.241.206 Deployer version: 1.0.14

Issue Description

New azd up deployments could fail during Gunicorn worker startup with a Cosmos DB error similar to:

Collection create forbidden as collection count in database offer has exceeded 25.

The application imports config.py during worker boot and opens or creates all SimpleChat Cosmos containers. The deployer created the SimpleChat database with shared autoscale throughput, and Cosmos DB limits shared-throughput databases to 25 containers. Current SimpleChat deployments require more than 25 application containers.

Root Cause Analysis

The deployment model used a provisioned Cosmos DB account, but attached the autoscale throughput offer to the SimpleChat SQL database. That made the database a shared-throughput database. When app startup reached the 26th container, Cosmos rejected the create operation even though the account itself was healthy and provisioned.

Technical Details

Files modified:

  • deployers/bicep/modules/cosmosDb.bicep
  • deployers/bicep/main.bicep
  • deployers/bicep/main.json
  • deployers/azurecli/deploy-simplechat.ps1
  • deployers/terraform/main.tf
  • deployers/version.txt
  • application/single_app/config.py
  • functional_tests/test_deployer_capacity_defaults.py
  • docs/explanation/features/v0.241.085/DEPLOYER_CAPACITY_DEFAULTS.md

Code changes summary:

  • Provisioned Cosmos deployments now create the SimpleChat SQL database without a shared database throughput offer.
  • SimpleChat containers are pre-created with dedicated autoscale throughput in provisioned mode.
  • The default autoscale max is now 1000 RU/s per container.
  • The existing cosmosDatabaseAutoscaleMaxThroughput Bicep parameter name is retained for deployment compatibility, but it now controls per-container autoscale max RU/s.
  • Serverless Cosmos deployments continue to create containers without throughput settings.

Testing Approach

Validation is covered by functional_tests/test_deployer_capacity_defaults.py, which checks the Bicep, generated one-click ARM template, Azure CLI deployer, Terraform deployer, documentation, application version, and deployer version.

Impact Analysis

New provisioned deployments avoid the shared-throughput 25-container limit and should no longer fail at startup when SimpleChat reaches containers such as public_workspace_identities.

Existing deployments that already have a shared-throughput SimpleChat database may require an intentional migration plan because removing a shared database throughput offer is not generally an in-place Bicep update. Those environments should be reviewed before rerunning infrastructure deployment.

Validation

Before:

  • azd up created a shared-throughput SimpleChat database.
  • App startup attempted to create more than 25 containers under that database offer.
  • Gunicorn workers failed to boot with the Cosmos container-count error.

After:

  • The deployer creates the database and all expected SimpleChat containers.
  • Provisioned throughput is assigned at the container level.
  • The app can open existing containers during startup without hitting the shared database container limit.