07 - Revisions and Traffic Splitting¶

Azure Container Apps revisions provide immutable deployment snapshots. Use them for safe releases, canary traffic, and quick rollback.

flowchart TD
    INET[Internet] -->|HTTPS| CA["Container App\nConsumption\nLinux Node 18 LTS"]

    subgraph VNET["VNet 10.0.0.0/16"]
        subgraph ENV_SUB["Environment Subnet 10.0.0.0/23\nDelegation: Microsoft.App/environments"]
            CAE[Container Apps Environment]
            CA
        end
        subgraph PE_SUB["Private Endpoint Subnet 10.0.2.0/24"]
            PE_ACR[PE: ACR]
            PE_KV[PE: Key Vault]
            PE_ST[PE: Storage]
        end
    end

    PE_ACR --> ACR[Azure Container Registry]
    PE_KV --> KV[Key Vault]
    PE_ST --> ST[Storage Account]

    subgraph DNS[Private DNS Zones]
        DNS_ACR[privatelink.azurecr.io]
        DNS_KV[privatelink.vaultcore.azure.net]
        DNS_ST[privatelink.blob.core.windows.net]
    end

    PE_ACR -.-> DNS_ACR
    PE_KV -.-> DNS_KV
    PE_ST -.-> DNS_ST

    CA -.->|System-Assigned MI| ENTRA[Microsoft Entra ID]
    CAE --> LOG[Log Analytics]
    CA --> AI[Application Insights]

    style CA fill:#107c10,color:#fff
    style VNET fill:#E8F5E9,stroke:#4CAF50
    style DNS fill:#E3F2FD

Revision Traffic Splitting¶

graph LR
    INGRESS[Ingress] -->|90%| V1[Revision v1]
    INGRESS -->|10%| V2[Revision v2]

Prerequisites¶

• Completed 06 - CI/CD with GitHub Actions
• At least two deployed images/tags

Step-by-step¶

1. Set standard variables

   RG="rg-nodejs-guide"
   BASE_NAME="nodejs-guide"
   DEPLOYMENT_NAME="main"
   
   APP_NAME=$(az deployment group show \
     --name "$DEPLOYMENT_NAME" \
     --resource-group "$RG" \
     --query "properties.outputs.containerAppName.value" \
     --output tsv)
   

2. Switch to multiple revision mode

   az containerapp revision set-mode \
     --name "$APP_NAME" \
     --resource-group "$RG" \
     --mode multiple
   

   Expected output

   "Multiple"
   

3. Deploy a new version to create a new revision

   az acr build --registry "$ACR_NAME" --image "$BASE_NAME:v3" ./apps/nodejs
   
   az containerapp update \
     --name "$APP_NAME" \
     --resource-group "$RG" \
     --image "$ACR_LOGIN_SERVER/$BASE_NAME:v3"
   

   Expected output

   az acr build takes 1-2 minutes. The az containerapp update returns:

   {
     "latestRevision": "<your-app-name>--xxxxxxx",
     "name": "<your-app-name>",
     "provisioningState": "Succeeded"
   }
   

4. List revisions and choose targets

   az containerapp revision list \
     --name "$APP_NAME" \
     --resource-group "$RG" \
     --query "[].{name:name,active:properties.active,createdTime:properties.createdTime}" \
     --output table
   

   Expected output

   Name                                     Active    CreatedTime
   ---------------------------------------  --------  -------------------------
   <your-app-name>--0000001                 True      2026-04-05T10:00:00+00:00
   <your-app-name>--0000002                 True      2026-04-05T10:15:00+00:00
   

5. Apply canary traffic split (90/10)

   # Capture revision names from the list above
   STABLE_REV="${APP_NAME}--0000001"
   CANARY_REV="${APP_NAME}--0000002"
   
   az containerapp ingress traffic set \
     --name "$APP_NAME" \
     --resource-group "$RG" \
     --revision-weight "$STABLE_REV=90" "$CANARY_REV=10"
   

   Expected output

   [
     {
       "revisionName": "<your-app-name>--0000001",
       "weight": 90
     },
     {
       "revisionName": "<your-app-name>--0000002",
       "weight": 10
     }
   ]
   

6. Rollback instantly if errors increase

   az containerapp ingress traffic set \
     --name "$APP_NAME" \
     --resource-group "$RG" \
     --revision-weight "$STABLE_REV=100"
   

   Expected output

   [
     {
       "revisionName": "<your-app-name>--0000001",
       "weight": 100
     }
   ]
   

7. Deactivate bad revision after confirmation

   az containerapp revision deactivate \
     --name "$APP_NAME" \
     --resource-group "$RG" \
     --revision "$CANARY_REV"
   

   Expected output

   "Deactivate succeeded"
   

Node.js Revision Management¶

When using multiple revisions with Node.js, ensure your application handles statelessness correctly. Session data should be stored in an external cache like Azure Cache for Redis to prevent user impact when traffic is split between different revisions.

Operational guidance¶

• Pair canary rollout with telemetry checks (errors, latency, saturation).
• Keep one prior known-good revision for emergency rollback.
• Use KEDA metrics and revision health together for rollout decisions.

Advanced Topics¶

• Route traffic by labels for blue/green style releases.
• Combine revisions with Dapr service invocation for progressive migration.
• Automate canary promotion in CI/CD using policy checks.

See Also¶

• 04 - Logging, Monitoring, and Observability
• 06 - CI/CD with GitHub Actions
• Revisions Operations

Sources¶

• Revisions (Microsoft Learn)
• Traffic splitting in Azure Container Apps (Microsoft Learn)