Docker in ProductionLesson 5.3

Docker resource limits and preventing container sprawl

--memory, --cpus, --memory-swap, cgroup limits, docker stats, resource starvation, OOM killer, resource reservation in Compose

Preventing a Runaway Container From Killing Your Host

Without limits, any container can consume all available host memory or CPU, starving other containers and the host OS. Always set limits in production.

Setting Limits at Runtime

# Limit to 512MB RAM and 0.5 CPU cores
docker run -d \
  --memory=512m \
  --cpus=0.5 \
  --memory-swap=512m \
  my-app

Setting --memory-swap equal to --memory disables swap, preventing the container from swapping to disk when it hits the memory ceiling. Instead, the Linux OOM killer terminates the container process — which is usually preferable to uncontrolled swap usage.

Monitoring Resource Usage

# Live resource stats for all running containers
docker stats

# One-time snapshot, no-stream
docker stats --no-stream

Limits in Docker Compose

services:
  api:
    deploy:
      resources:
        limits:
          cpus: "0.5"
          memory: 512M
        reservations:
          memory: 256M

reservations guarantee a minimum amount of resources; limits set the maximum. Compose deploy resource limits apply when using docker compose with the --compatibility flag or Docker Swarm.