Docker Stack

A production-style containerized application stack with full observability

Overview

This project is a fully containerized application stack built with production practices in mind. It runs a Flask web application backed by MySQL, served through NGINX as the sole public entry point. On top of that, a complete observability layer is wired in — Prometheus collects metrics from every service, Loki aggregates all container logs, and Grafana provides 7 pre-built dashboards covering the full stack.

🏗️ Architecture Overview

Dockerfile Linting

Hadolint is used to lint app/Dockerfile against Dockerfile best-practice rules. Configuration lives in .hadolint.yaml at the project root.

Run hadolint

Docker (no install needed):

docker run --rm -i hadolint/hadolint < app/Dockerfile

With the project config applied:

docker run --rm -i \
  -v "$(pwd)/.hadolint.yaml:/.config/hadolint.yaml" \
  hadolint/hadolint < app/Dockerfile

If hadolint is installed locally:

hadolint --config .hadolint.yaml app/Dockerfile

Ignored rule

DL3008 — Pin versions in apt-get install — is intentionally ignored.

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Prerequisites

• Docker 20.10+ and Docker Compose v2
• Secrets files must exist before starting:

echo -n "root"  > secrets/db_root_pw.txt
echo -n "admin" > secrets/db_admin_pw.txt

Start

./scripts/start.sh

All 10 services start in dependency order. MySQL initializes the schema on first boot (db/init/01_schema.sql). Flask waits for MySQL to be healthy before starting. NGINX waits for Flask.

Stop

./scripts/stop.sh

Containers are removed, all named volumes (data) are preserved. To also wipe data:

docker compose down -v

Rebuild the Flask image

docker compose build flask-app
docker compose up -d flask-app

View logs

docker compose logs -f                  # all services
docker compose logs -f flask-app mysql  # specific services

Check service status

docker compose ps

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Access

Interface	URL	Credentials
Application	http://localhost	—
Grafana	http://localhost:3000	admin / admin
Prometheus	http://localhost:9090	—
Alloy UI	http://localhost:12345	—
cAdvisor	http://localhost:8080	—
mysqld-exporter	http://localhost:9104/metrics	—
Blackbox Exporter	http://localhost:9115	—

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Observability

Metrics

Prometheus scrapes 6 targets every 15 seconds with 15-day retention:

Job	Source	What it measures
flask-app	Flask /metrics	Request rate, latency (p50/p95/p99), error rate per endpoint
cadvisor	cAdvisor	Per-container CPU, memory, network, filesystem
mysqld-exporter	mysqld-exporter	Query throughput, connections, InnoDB buffer pool, slow queries
blackbox-http	Blackbox → NGINX	HTTP uptime, status code, response time phases
blackbox-exporter	Blackbox self	Exporter health
prometheus	Prometheus self	Scrape health, TSDB stats

Alloy also collects host-level metrics (CPU, memory, disk, network) via its built-in node exporter and pushes them to Prometheus via remote_write.

Logs

Alloy tails all container logs via the Docker socket and ships them to Loki with container and service labels. MySQL slow query log gets special treatment — multiline entries are reassembled and the query_time label is extracted for filtering.

Dashboards

7 pre-provisioned Grafana dashboards, auto-loaded on startup:

Dashboard	Data Source	What's inside
Stack Overview	Prometheus + Loki	Single-pane-of-glass — all service health, links to every other dashboard
Flask Application	Prometheus	Request rate, error rate, p50/p95/p99 latency, per-endpoint breakdown
Docker Containers	Prometheus	Per-container CPU, memory, network — links to logs
MySQL	Prometheus + Loki	Query throughput by type, connections, InnoDB, slow query log panel
Container Logs	Loki	Live log viewer, log volume, MySQL slow log, journal errors
Node Exporter Full	Prometheus	Full host system metrics
Prometheus Blackbox Exporter	Prometheus	HTTP probe status, response time breakdown by phase

Dashboards are cross-linked — container metrics panels link directly to Container Logs filtered to that container.

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Secrets

Database credentials are managed via Docker Secrets — never plain environment variables.

secrets/
├── db_root_pw.txt    # MySQL root password
└── db_admin_pw.txt   # MySQL app user password (used by Flask + mysqld-exporter)

See secrets/README.md.

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Project Structure

docker-stack/
├── docker-compose.yml
├── .hadolint.yaml              # Hadolint Dockerfile linting config
├── app/                        # Flask application
│   ├── Dockerfile
│   ├── app.py
│   ├── requirements.txt
│   └── templates/index.html
├── configs/                    # All service configs (mounted read-only)
│   ├── nginx/default.conf
│   ├── prometheus/prometheus.yml
│   ├── loki/loki.yml
│   ├── alloy/config.alloy
│   ├── blackbox/blackbox.yml
│   └── grafana/provisioning/
│       ├── datasources/        # Prometheus + Loki auto-wired
│       └── dashboards/json/    # 7 pre-built dashboards
├── db/init/01_schema.sql       # MySQL schema, auto-run on first start
├── secrets/                    # Never committed — gitignored
│   ├── db_root_pw.txt
│   └── db_admin_pw.txt
└── scripts/
    ├── start.sh                # docker compose up -d
    └── stop.sh                 # docker compose down (volumes preserved)

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Screenshots

Application

Prometheus Targets

Alloy

Grafana