A production-style application deployment rarely succeeds on the first attempt.
This project implemented a containerized multi-service architecture using Docker Compose, integrating Flask as the application layer, PostgreSQL as the persistence layer, Gunicorn as the WSGI runtime, and NGINX as the reverse proxy ingress service.
The intended architecture was:
Client → NGINX → Flask → PostgreSQL
The objective extended beyond simply getting containers running.
The implementation focused on:
- Multi-container orchestration
- Reverse proxy traffic routing
- Inter-service communication
- Stateful persistence with Docker volumes
- Environment variable injection
- Runtime debugging and remediation
- Container observability and diagnostics
Several deployment failures occurred during implementation, each requiring troubleshooting and root cause analysis.
Issues encountered included:
Docker Compose manifest discovery failure due to incorrect directory placement.
Docker image build failures caused by malformed Dockerfile syntax.
Gunicorn runtime crashes resulting from incorrect CMD formatting.
NGINX ingress failure caused by invalid directive syntax ("listens" instead of "listen").
Flask runtime exceptions caused by Python syntax, indentation, and environment variable errors.
Each failure required log inspection, iterative debugging, configuration correction, rebuild execution, and container redeployment.
Validation was performed using:
docker compose logs -f
docker ps
docker volume ls
curl endpoint verification
Final deployment confirmed successful end-to-end communication between NGINX, Flask, and PostgreSQL.
This article documents the complete deployment lifecycle, architecture decisions, failure analysis, remediation strategy, and operational lessons learned while building the stack.
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