The Complete Docker Compose Monitoring Guide

You have deployed your stack with Docker Compose. Your containers are running. Everything seems to be working. But what happens when something breaks at 3 AM?

This guide covers the 6 essential dimensions of monitoring for Docker Compose, and how to set them up effectively.

1. Container Monitoring

The most basic level: are your containers running?

What to Watch

Container state – running, stopped, restarting, exited
Restart loops – a container stuck in a restart loop is often worse than one that has stopped entirely
Docker health checks – Docker’s native HEALTHCHECK is underused but extremely valuable
Exit codes – a non-zero exit code indicates a crash, not a clean shutdown

Health Checks in Your docker-compose.yml

services:
  api:
    image: myapp:latest
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 40s

Maintenant automatically reads Docker health check results and alerts you when a container transitions to unhealthy.

Container monitoring — states, health checks, restart loops

2. Endpoint Monitoring

Verifying that your services respond correctly to requests.

HTTP Checks

Beyond simply asking “does it respond”, a proper HTTP check verifies:

The status code (200, 201, etc.)
The response time (latency)
The response content (body assertion)
SSL certificate validity

With Maintenant, you configure this directly through Docker labels:

labels:
  maintenant.endpoint.http: "https://api.example.com/health"
  maintenant.endpoint.interval: "30s"
  maintenant.endpoint.http.expected-status: "200"

HTTP/TCP endpoint monitoring — latency, status codes

TCP Checks

For services that do not speak HTTP – databases, Redis, MQTT – a TCP check verifies that the port is open and accepting connections:

labels:
  maintenant.endpoint.tcp: "postgres:5432"

3. SSL Certificate Monitoring

Expired certificates are one of the most common causes of preventable downtime. With Let’s Encrypt and automatic renewal, it is tempting to assume everything just works. But renewals can fail silently.

Maintenant automatically detects SSL certificates on all your HTTPS endpoints and alerts you at 30, 14, 7, 3, and 1 day before expiration.

SSL/TLS certificate tracking — expiration, chain validation

4. Cron Job Monitoring

Scheduled tasks are the most overlooked services. Is your nightly backup actually running? Did your cleanup job finish successfully?

The heartbeat pattern: your cron sends a ping to a URL after each execution. If the ping does not arrive within the expected window, you get alerted.

Heartbeat monitoring — cron jobs, scheduled tasks

# Add a line to your crontab
0 3 * * * /usr/local/bin/backup.sh && curl -fsS -o /dev/null https://now.example.com/ping/{uuid}/$?

5. System Resource Monitoring

Critical Metrics

Disk space – a full disk can crash your database
Memory usage – per container and per host
CPU – to detect abnormal spikes
Network I/O – to identify congestion

Maintenant collects these metrics via the Docker stats API and displays them in real time with historical graphs.

System resources — CPU, memory, disk, network per container

6. Update Detection

Knowing that a security update is available for your PostgreSQL or Redis image is critical. Maintenant scans OCI registries and compares digests to alert you when updates are available.

Update intelligence — critical, available, pinned versions

Setting It All Up in 30 Seconds

With Maintenant, all 6 monitoring dimensions are covered by a single container:

services:
  maintenant:
    image: ghcr.io/kolapsis/maintenant:latest
    ports:
      - "8080:8080"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - /proc:/host/proc:ro
      - maintenant-data:/data
    environment:
      MAINTENANT_ADDR: "0.0.0.0:8080"
      MAINTENANT_DB: "/data/maintenant.db"
    restart: unless-stopped

volumes:
  maintenant-data:

Your containers are discovered automatically. Add labels for endpoints and alerts. That is it.

Install Maintenant –>