Introduction: A Developer’s Journey into the Unknown
When I first started working with Docker, I had little to no knowledge about hosting, ports, IPs, or managing containers. My experience was limited to running basic commands like:
- `docker ps` (to check active containers)
- `docker ps -a` (to list all containers)
Then came a real-world challenge: managing a system that used Django as a backend and an older version of Vue (Vuetify I think) on the frontend. This system was hosted on a server configured with `supervisorctl`, `uwsgi`, and `nginx`—a setup that seemed overwhelming at first.
Transitioning from a traditional server configuration to a fully containerized application was a daunting task. First, I learned how to back up databases, then gradually grasped key Nginx directives, and eventually understood domain hosting.
A crucial resource in my learning process was this tutorial: Deploying a Django Application with Docker, Nginx, and Certbot. Through hands-on experimentation, I improved my `docker-compose.yml` configuration, enhanced my understanding of Docker containers, and optimized GitLab CI/CD workflows. Things were going smoothly—until the unexpected happened.
The Unexpected Problem: A Mysterious Database Failure
The trouble began with an unusual backup stored in a development volume.
I remember thinking, Why is this backup in the development container? I thought I placed it in the production volume. Well, maybe I just forgot. I dismissed the anomaly and moved on.
Then came _Saturday_, between 9 AM and 11 AM. I was running my final checks to ensure everything was functioning properly. I monitored the requests, verifying that all responses returned `200 OK`. Everything seemed fine.
At 12 AM, disaster struck.
Every request started returning 500 Internal Server Error.
Panic Mode: The Fear of Failure
I was terrified. The system had been down for two hours. Users started calling, demanding answers. I frantically searched for clues and eventually spotted an error in the production database container: `No such directory ...`.
But what directory was missing?
At that time, my database knowledge was limited. I turned to Stack Overflow, but every solution I found seemed foreign and confusing. To make matters worse, I couldn’t access either my development or production PostgreSQL databases—they were both corrupted.
Picture this: a Docker newbie, managing a crucial system that handled commercial transactions, suddenly facing total system failure. Users were unable to create or update orders for their clients. I felt an overwhelming sense of responsibility. My mind raced: What is happening? People are counting on me. I need to fix this—fast!
For a brief moment, paranoia set in. Is this a hacker attack? I desperately wanted to believe an external force was responsible rather than confront my own potential mistakes.
Then, a nagging thought resurfaced: Why was the production backup also present in the development environment?
Hours before the crash, both environments were functioning correctly. So why did the system break when real users started using it?
The Turning Point: A Lesson in Action Over Analysis
At the time, I didn’t have the luxury of deep analysis. My boss, who also didn’t know the exact cause of the issue, gave me a simple yet powerful directive:
“Restart everything. Restore the data. Hurry up.” -- My boss
I deleted the corrupted production database and restored a backup from 30 minutes before the failure. Once the backup was applied and the database container restarted, the system was back online. Users resumed their tasks, and operations returned to normal.
But the root cause of the failure still eluded me.
As I reviewed the backup files, I noticed something strange—both the production and development database backups were stored in the same location. That’s when I decided to take a closer look at my `docker-compose.yml` files.
The Hidden Error: A Simple Yet Costly Mistake
Comparing my Docker Compose files, I discovered a glaring mistake.
Development docker-compose.yml:
db_service:
volumes:
- my_vol:/some/dir
volumes:
my_vol:
Production docker-compose.yml
db_service:
volumes:
- my_vol:/some/dir
volumes:
my_vol:
At first glance, they seemed identical. But that was precisely the problem.
Both environments were using the same named volume: my_vol. This meant that Docker was not treating them as separate entities—instead, both environments were unknowingly sharing the same database volume.
Why Was This a Problem?
For a while, it didn’t cause any issues because the development and production environments weren’t used simultaneously. However, once real users started interacting with the system, conflicts emerged. Different database requests from separate environments began colliding, corrupting both databases.
The Solution: Isolating Environments Properly
To prevent this from happening again, I changed the volume names in each environment to ensure proper isolation.
Fixed Development docker-compose.yml:
db_service:
volumes:
- dev_vol:/some/dir
volumes:
dev_vol:
Now, Docker treated the development and production databases as completely separate entities, eliminating the risk of accidental data overlap.
Final Thoughts: Lessons from a Near-Disaster
Looking back, this experience taught me several invaluable lessons:
- Separate Development and Production Environments – Never let them share the same resources unintentionally.
- Backups Are Lifesavers – Having a recent backup prevented a complete data loss disaster.
- Action Over Analysis – While understanding the root cause is important, taking quick action in emergencies is sometimes more critical.
- Continuous Learning – Every mistake is an opportunity to improve.
In the end, what started as a terrifying crisis became a powerful learning experience. I emerged from this challenge with a stronger grasp of Docker, database management, and production deployment strategies.
To all developers facing unexpected system failures—stay calm, act quickly, and most importantly, learn from your mistakes. You’ll come out stronger on the other side.