Claude-Dockerizing a NestJS API with Multi-Environment Support

Prompt:

I have nestjs api backend node application that I want to dockerize it. I will use docker compose for the ease of management. I will have atleast 3 environments: dev, test and prod which I want to support running those docker instances in my EC2 machine running Amazon Linux simultaneously. There will be separate env input files such as env.dev, env.test which defines the environment values. 1. Provide me single Dockerfile supporting multiple environments using NODE_ENV environment variable. 2. Also provide me single docker compose yml file supporting multiple environments by treating each environment as a separate project env. 3. Also Provide me single helper script with minimal util functions mainly for ease of management of build and deploy using primarily docker compose commands. This script can be used to source from any other custom scripts.

Response:

I'll help you create a Docker setup for your NestJS application that supports multiple environments.

Multi-Environment Dockerfile

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Multi-Environment Docker Compose

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Docker Helper Script

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Let me explain each component:

Dockerfile:
- Uses multi-stage build to optimize image size
- Accepts NODE_ENV as build argument
- Copies appropriate environment file based on NODE_ENV
- Uses Node 18 Alpine for smaller image size
- Separates build and runtime stages
docker-compose.yml:
- Uses YAML anchors to avoid repetition
- Defines separate services for each environment
- Maps different ports for each environment (3000, 3001, 3002)
- Uses environment-specific env files
- Includes volume mapping for logs
- Configures restart policy
Helper Script:
- Provides common functions for managing Docker environments
- Includes logging with color coding
- Supports environment validation
- Functions include:
  - build_app: Build for specific environment
  - start_app: Start containers
  - stop_app: Stop containers
  - restart_app: Restart containers
  - view_logs: View container logs
  - cleanup: Clean up resources
  - status: Show container status

To use this setup:

Save the files in your project root:
- Dockerfile
- docker-compose.yml
- docker-helper.sh
Create environment files:
- env.dev
- env.test
- env.prod
Make the helper script executable:
```
chmod +x docker-helper.sh
```

Use the helper script:

# Build and start dev environment
./docker-helper.sh build dev
./docker-helper.sh start dev

# View logs
./docker-helper.sh logs dev

# Check status of all environments
./docker-helper.sh status

You can also source the helper script in other scripts:

source ./docker-helper.sh
build_app "dev"
start_app "dev"

Would you like me to explain any part in more detail or make any modifications to the configuration?

Prompt:

I want you to update the docker-compose.yml file: 1. Remove version as it is deprecated; 2. I don't need x-app-common; 3. Define single service called mf-api -- the image, container, args, ports, environment will be dependent on dynamic environment values; 4. There are only couple of build stage env variables and there are more than 10 run time specific environment variables. Only for few of them, I may provide default values and for others, I may just list them in ARGS and in environment sections without specifying any defaults -- This assumes that the docker compose would automatically pass the env values of the listed ones and pass it as args when invoking the docker instance. Please clarify.

Response:

I'll update the docker-compose.yml file to match your requirements.

Updated Docker Compose with Dynamic Environment

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Let me explain the key changes and how environment variables work in this setup:

Version Removal: Removed the version field as it's no longer needed in recent Docker Compose versions.
Single Dynamic Service:
- Service name is now mf-api
- Image and container names use ${NODE_ENV} for environment-specific naming
Build Arguments vs Runtime Environment:
- Build arguments (args) are used during image build time
- Environment variables are used when the container runs
Environment Variable Handling:
- Variables with defaults use the syntax: VARIABLE: ${VARIABLE:-default_value}
- Variables without defaults use the list syntax: - VARIABLE
- When listed without defaults, Docker Compose will:
  - First look for the variable in the shell environment
  - Then look in the environment file specified by env_file
  - Pass through the value if found, or empty if not found
Important Clarifications:
- Variables listed under environment without defaults MUST be:
  - Defined in your shell environment, OR
  - Defined in your environment file (env.${NODE_ENV}), OR
  - Defined in a .env file in the same directory as docker-compose.yml
- Docker Compose will automatically pass these variables to the container
- If a variable is not found anywhere, it will be passed as an empty string

To use this setup:

# Example 1: Running with minimal configuration
NODE_ENV=dev docker compose up

# Example 2: Running with specific variables
export DATABASE_URL=postgresql://user:pass@host:5432/db
export REDIS_URL=redis://localhost:6379
NODE_ENV=prod docker compose up

# Example 3: Running with a different port
NODE_ENV=test API_PORT=3001 docker compose up

You can also create a .env file in your project root to provide default values:

DATABASE_URL=postgresql://user:pass@host:5432/db
REDIS_URL=redis://localhost:6379
AWS_REGION=us-east-1
# ... other variables

Would you like me to:

Add or remove any environment variables?
Modify how any of the variables are handled?
Add additional configuration options to the service?

Prompt:

within build:args, for example, we have API_VERSION without any default values. Would docker compose will pickup $API_VERSION from the shell environment and pass it or is there a specific syntax to pass these values using docker compose build ?

Response:

Let me clarify how build arguments work in Docker Compose, particularly for arguments without default values.

There are two ways to handle build arguments in Docker Compose:

Using the environment variable reference syntax:

build:
  args:
    API_VERSION: ${API_VERSION}

Using the list syntax (what we had before):

build:
  args:
    - API_VERSION

The key difference is:

The list syntax (- API_VERSION) does NOT automatically pick up values from the shell environment during build
The environment variable reference syntax (API_VERSION: ${API_VERSION}) WILL pick up values from the shell environment

Let me update the docker-compose.yml to use the correct syntax:

Docker Compose with Correct Build Args Syntax

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To build using these build arguments, you would:

# Method 1: Export variables before building
export API_VERSION=1.2.3
export APP_BUILD_CONFIG=prod
docker compose build

# Method 2: Specify variables in command line
docker compose build --build-arg API_VERSION=1.2.3 --build-arg APP_BUILD_CONFIG=prod

# Method 3: Use .env file with the build arguments defined
# .env file:
# API_VERSION=1.2.3
# APP_BUILD_CONFIG=prod
docker compose build

I've also updated the environment variables section to use the same reference syntax for consistency. This makes it clearer what variables are being passed and allows for better error handling if required variables are missing.

Would you like me to:

Add more examples of how to use build arguments?
Explain how to handle build arguments in the Dockerfile?
Show how to verify that build arguments are being passed correctly?

Prompt:

Okay, however the treatment inside environment: section is different; If I have REDIS_URL without specifying value OR REDIS_URL: {VAR}, we can just say - VAR ?

Response:

Yes, you're absolutely correct! When it comes to runtime environment variables (under environment:), both syntaxes work the same way:

environment:
  - REDIS_URL                 # Simple list syntax

is functionally equivalent to:

environment:
  REDIS_URL: ${REDIS_URL}    # Explicit reference syntax

Both will:

Look for REDIS_URL in the shell environment
Look in the env_file if not found in shell
Pass an empty string if not found anywhere

Let me update the docker-compose.yml to use the simpler list syntax for runtime environment variables:

Docker Compose with Simplified Environment Variables

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The key differences in this updated version:

Build args still use ARG: ${ARG} syntax because they need explicit reference
Environment variables with defaults still use VAR: ${VAR:-default} syntax
Environment variables without defaults now use the simpler - VAR list syntax

This makes the configuration cleaner and more maintainable while achieving the same functionality. Would you like me to make any other adjustments to the configuration?

Prompt:

I need a minimal helper script to manage with docker compose build, up and down operations. Unless we use env specific projects (with -p option), docker compose up terminates other running instances belonging to other environment. So I need a shell function like api_manage up/down/destroy/status/logs which will internally make use of NODE_ENV and corresponding project with docker compose operations.

Response:

Docker Compose Helper Script

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To use this script:

Save it as api-helper.sh and make it executable:

chmod +x api-helper.sh

Source it in your shell or other scripts:

source api-helper.sh

Use it with different environments:

# Start dev environment
NODE_ENV=dev api_manage up

# Start test environment (runs alongside dev)
NODE_ENV=test api_manage up

# Check status of prod environment
NODE_ENV=prod api_manage status

# View logs for test environment
NODE_ENV=test api_manage logs

# Bring down dev environment only
NODE_ENV=dev api_manage down

# Completely remove test environment
NODE_ENV=test api_manage destroy

Key features:

Uses project names (-p option) to isolate environments
Supports running multiple environments simultaneously
Provides common operations (up, down, destroy, build, status, logs)
Falls back to default environment if NODE_ENV not set
Can be sourced in other scripts or run directly

Would you like me to:

Add more commands or features?
Add error handling for specific scenarios?
Add support for additional environment variables?

Prompt:

Error response from daemon: Invalid container name (mfapi:local), only [a-zA-Z0-9][a-zA-Z0-9.-] are allowed

Response:

Ah, this error occurs because Docker has strict naming conventions for containers. Let me update the docker-compose.yml and helper script to ensure we use only allowed characters (replacing underscores with hyphens):

Docker Compose with Valid Container Names

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Updated Docker Helper Script

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Key changes made:

In docker-compose.yml:
- Changed image and container names to use dots instead of underscores (mf-api.${NODE_ENV})
- Ensured all names use valid characters
In the helper script:
- Added sanitization of environment names using tr '_' '-'
- Updated project name generation to ensure valid characters

Now you can use it the same way:

NODE_ENV=dev api_manage up
NODE_ENV=test api_manage up
NODE_ENV=prod api_manage status

The script will automatically convert any invalid characters to valid ones, ensuring Docker accepts the names. Let me know if you'd like any adjustments to this solution!

Prompt:

I need to choose proper docker base image for build stage; I am using node:22-slim as per latest recommendations, but got prisma error: #10 0.696 Please manually install OpenSSL via apt-get update -y && apt-get install -y openssl and try installing Prisma again. If you're running Prisma on Docker, add this command to your Dockerfile, or switch to an image that already has OpenSSL installed. I want fairly recent one for base image for builder; Please suggest;

Response:

For a Node.js application using Prisma, you'll want a base image that includes the necessary system dependencies. Here are some good options:

Using node:20-bookworm-slim (recommended):

FROM node:20-bookworm-slim AS builder

# Install OpenSSL and other required dependencies
RUN apt-get update -y && \
    apt-get install -y openssl pkg-config libssl-dev && \
    rm -rf /var/lib/apt/lists/*

Using node:20 (includes more dependencies but larger size):

FROM node:20 AS builder
# No need to install additional dependencies

Using node:20-slim with minimal dependencies:

FROM node:20-slim AS builder

# Install only OpenSSL
RUN apt-get update -y && \
    apt-get install -y openssl && \
    rm -rf /var/lib/apt/lists/*

I recommend going with option 1 (node:20-bookworm-slim) because:

Node.js 20 is the current LTS version with long-term support until April 2026
The bookworm variant is based on Debian 12 which has newer system libraries
The slim variant provides a good balance between image size and included dependencies
Including pkg-config and libssl-dev helps avoid other potential dependency issues

Let me update the full Dockerfile with this recommendation:

Updated Dockerfile with Prisma Support

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Key changes:

Changed base image to node:20-bookworm-slim
Added required dependencies for Prisma in build stage
Added minimal dependencies in production stage
Added Prisma client generation step
Copying node_modules from builder to include Prisma client

Would you like me to:

Explain more about the different Node.js Docker image variants?
Add any other dependencies for your specific use case?
Optimize the image size further?

Prompt:

Error: Cannot find module '/app/node dist/main'

Response:

That error occurs because there's an extra space in the CMD instruction. Let me fix the Dockerfile:

Fixed Dockerfile with Correct CMD

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The key fix was in the last line:

Wrong: CMD ["node", "node dist/main"] or CMD ["node dist/main"]
Correct: CMD ["node", "dist/main"]

The CMD instruction needs to be an array of strings where:

First element is the executable ("node")
Subsequent elements are the arguments ("dist/main")

You should now be able to run the container without the module not found error. Would you like me to add any additional changes or explain more about Dockerfile CMD syntax?