When moving a legacy app to containers, you have to check on the dependencies, compatibility, and security needs. The dependencies on different libraries, databases, and external services it uses need to be enumerated. Then create a Dockerfile which replicates the app's environment: its OS version, the required libraries, and its configurations.
Best Practices include:
Base Image Selection : One should begin with an output size minimal image, ubuntu, or alpine.
Dependency Management: Only optional dependencies should be installed in the Dockerfile to avoid littering and bloat.
Data Persistence: For data that needs persistency, use Docker volumes as a means to segregate from containerized processes.
Security: Vulnerability scanning should be done using integration tools, and not hardcoded sensitive information but rather passed through environment variables.
When the application is containerized, ensure to test it in isolation before integrating with other systems of production.
Migrating a legacy app to containers involves creating a Dockerfile that captures the app’s dependencies, environment, and runtime. Below is an example Dockerfile for a Node.js app:
This Dockerfile sets up a container for a Node.js app by specifying the environment and dependencies needed, simplifying deployment and scaling.
