01 - Run Locally with Docker¶

Before deploying to Azure Container Apps, validate your Node.js app in a container locally. This catches image, dependency, and port issues early.

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

Local Development Workflow¶

graph TD
    CODE[Source Code] --> BUILD[Docker Build]
    BUILD --> CONT[Container]
    CONT --> LOCAL[localhost:8000]
    LOCAL --> HEALTH[Health Check]

Prerequisites¶

• Docker Engine or Docker Desktop
• Node.js and npm installed
• Source code with a Dockerfile

Step-by-step¶

1. Build the container image

   cd apps/nodejs
   docker build --tag aca-nodejs-guide .
   

   Expected output

   [1/5] FROM docker.io/library/node:20-slim
   [2/5] WORKDIR /app
   [3/5] COPY package*.json ./
   [4/5] RUN npm install --omit=dev
   [5/5] COPY src/ ./src/
   Successfully tagged aca-nodejs-guide:latest
   

2. Run the container locally

   # Copy and customize the environment file
   cp .env.example .env
   
   docker run --publish 8000:8000 --env-file .env aca-nodejs-guide
   

   Expected output

   {"timestamp":"2026-04-05T10:00:00.000Z","level":"INFO","message":"Server started on port 8000"}
   

3. Verify health endpoint

   curl http://localhost:8000/health
   

   Expected output

   {"status":"healthy","timestamp":"2026-04-05T10:01:00.000Z"}
   

   You can also verify runtime metadata:

   curl http://localhost:8000/info
   

   Expected output

   {"app":"azure-container-apps-nodejs-guide","version":"1.0.0","runtime":{"node":"v20.20.2","platform":"linux","arch":"x64"}}
   

4. Inspect application logs

   docker logs <container-id>
   

   Expected output

   {"timestamp":"2026-04-05T10:00:00.000Z","level":"INFO","message":"Server started on port 8000"}
   {"timestamp":"2026-04-05T10:01:00.000Z","level":"INFO","method":"GET","url":"/health","status":200}
   

   To find the container ID: docker ps

Local parity checklist¶

• Application listens on port 8000 (or your configured container port)
• Required environment variables are present
• /health returns HTTP 200
• No startup exceptions in container logs

Advanced Topics¶

• Use multi-stage Docker builds to keep your production image lean and secure.
• Use node --watch during development to automatically restart the server on file changes.
• Add local Redis or MongoDB via docker-compose to mimic cloud dependencies.

Review Matrix¶

See Also¶

• 02 - First Deploy to Azure Container Apps
• 03 - Configuration, Secrets, and Dapr
• Recipes Index

Sources¶

• Quickstart: Code to Cloud (Microsoft Learn)
• Dockerfile requirements for Azure Container Apps (Microsoft Learn)