The second factor of the Twelve-Factor App methodology highlights the importance of explicitly declaring and isolating these dependencies.
Why Declare and Isolate Dependencies?
Declaring and isolating dependencies ensures that the application is self-contained and does not rely on the implicit existence of system-wide packages.
- Reproducibility: Ensures that the application runs consistently across different environments.
- Scalability: Facilitates easy scaling without conflicts between dependencies.
- Security: Allows for targeted updates and monitoring of specific dependencies.
How to Declare and Isolate Dependencies
Use Dependency Management Tools
Modern programming languages offer package managers to handle dependencies, such as:
- Maven for Java
- Pip for Python
Example: Using Pip for Python
pip install -r requirements.txt
requirements.txt lists the dependencies:
Containers like Docker ensure that dependencies are isolated and consistent across different environments.
FROM python:3.8 COPY requirements.txt . RUN pip install --no-cache-dir -r requirements.txt
Deployment Strategies with Dependencies
In a pipeline, dependencies must be handled at the build stage, ensuring the application has everything it needs before deployment.
- Build Stage: Install dependencies using a package manager.
- Test Stage: Run tests to verify that dependencies are functioning correctly.
- Deployment Stage: Deploy the application along with its dependencies to the target environment.
Managing dependencies explicitly is essential for maintaining a robust, scalable, and secure application.